UTILIZATION STUDIES AND

RESIDUAL MEASUREMENTS

INTERAGENCY TECHNICAL REFERENCE
Supersedes BLM Technical Reference 4400-3, Utilization Studies, dated September 1984

Edited, designed, and produced by the Bureau of Land Management’s

National Applied Resource Sciences Center

BLM/RS/ST-96/004+1730

Utilization Studies and Residual Measurements

Interagency Technical Reference

Cooperative Extension Service

U.S. Department of Agriculture

—Forest Service—

Natural Resource Conservation Service,

Grazing Land Technology Institute

U.S. Department of the Interior

—Bureau of Land Management—

1996

Revised in 1997, 1999
TABLE OF CONTENTS

UTILIZATION STUDIES AND

RESIDUAL MEASUREMENTS

Interagency Technical Reference

By (In alphabetical order)

Technical Reference 1734-3

copies available from

Bureau of Land Management

National Business Center

BC-650B

P.O. Box 25047

Denver, Colorado 80225-0047

Bill Coulloudon

Rangeland Management Spec.

Bureau of Land Management

Phoenix, Arizona

Kris Eshelman (deceased)

Rangeland Management Spec.

Bureau of Land Management

Reno, Nevada

James Gianola

Wildhorse and Burro Spec.

Bureau of Land Management

Carson City, Nevada

Ned Habich

Rangeland Management Spec.

Bureau of Land Management

Denver Colorado

Lee Hughes

Ecologist

Bureau of Land Management

St. George, Utah

Curt Johnson

Rangeland Management Spec.

Forest Service Region 4

Ogden Utah

Mike Pellant

Rangeland Ecologist

Bureau of Land Management

Boise, Idaho

Paul Podborny

Wildlife Biologist

Bureau of Land Management

Ely, Nevada

Allen Rasmussen

Rangeland Management Spec.

Cooperative Extension Service

Utah State University

Logan, UT

Ben Robles

Wildlife Biologist

Bureau of Land Management

Safford, Arizona

Pat Shaver

Natural Resource Conservation Service

Rangeland Management Spec.

Corvallis, Oregon

John Spehar

Rangeland Management Spec.

Bureau of Land Management

Rawlins, Wyoming

John Willoughby

State Biologist

Bureau of Land Management

Sacramento, California
TABLE OF CONTENTS

TABLE OF CONTENTS

I. PREFACE ...................................................................................................................... i

II. INTRODUCTION ....................................................................................................... 1

A. Terms and Concepts ............................................................................................... 1

B. Guidelines............................................................................................................... 2

C. Location of Sample Sites......................................................................................... 2

D. Key Species ............................................................................................................. 4

E. Coordination........................................................................................................... 5

F. Electronic Data Recorders ...................................................................................... 5

III. STUDY DESIGN AND ANALYSIS ............................................................................. 7

A. Planning the Study .................................................................................................. 7

B. Statistical Considerations ...................................................................................... 11

C. Collecting Utilization Data and Residue Measurements ....................................... 17

D. Other Important Considerations ........................................................................... 19

IV. UTILIZATION PATTERNS (USE ZONES) ............................................................... 23

A. Base Map for Displaying Utilization Patterns ........................................................ 23

B. Mapping Utilization Patterns ................................................................................ 23

V. METHODS ................................................................................................................ 25

A. Browse Removal Methods..................................................................................... 25

1. Twig Length Measurement Method ................................................................ 25

2. Cole Browse Method ...................................................................................... 34

3. Extensive Browse Method............................................................................... 43

B. Residue Measuring Methods ................................................................................. 51

1. Stubble Height Method .................................................................................. 51

2. Visual Obstruction Method - Robel Pole ........................................................ 57

3. Comparative Yield Method ............................................................................. 62

C. Herbaceous Removal Methods.............................................................................. 70

1. Paired Plot Method ......................................................................................... 70

2. Ocular Estimate .............................................................................................. 76

3. Key Species Method (formerly the Modified Key Forage Plant Method)......... 81

4. Height-Weight Method ................................................................................... 89

5. Actual Weight Method.................................................................................. 103

6. Grazed-Class Method ................................................................................... 109

D. Qualitative Assessments - Landscape Appearance Method ................................. 119

(formerly the Key Forage Plant Method)

E. Other Methods ................................................................................................... 126

1. Stem Count .................................................................................................. 126

2. Community Structure Analysis ..................................................................... 126

3. Herbage Capacitance Meter .......................................................................... 126

VI. GLOSSARY OF TERMS .......................................................................................... 127

VII. REFERENCES .................................................................................................... 135
TABLE OF CONTENTS

TABLE OF CONTENTS (continued)

APPENDIXES

Appendix A Study Location and Documentation Data Form ....................................... 141

Appendix B Study Identification .................................................................................. 145

Appendix C Transect Schematic (Selecting the Nearest Plant) ..................................... 147

Appendix D Degrees of Hedging .................................................................................. 149

Appendix E Utilization Cages ...................................................................................... 151

Appendix F Selecting Random Samples (Using Random Number Tables) ................... 163

Illustration Title Page

Number

1........................Twig Length Measurement Form.............................................. 30-33

2........................Cole Browse Form .................................................................... 39-42

3........................Extensive Browse Form ............................................................ 48-50

4........................Stubble Height Form ................................................................53-56

5........................Robel Pole Form ....................................................................... 59-60

6........................Robel Pole ..................................................................................... 61

7........................Comparative Yield Form .......................................................... 67-68

8........................Comparative Yield Quadrat Frame ................................................ 69

9........................Paired Plot Form ....................................................................... 74-75

10.......................Ocular Estimate Form .............................................................. 79-80

11.......................Key Species Form ..................................................................... 86-88

12.......................Height-Weight Form ................................................................95-96

13.......................Height-Weight Utilization Gauge............................................. 97-99

14.......................Height-Weight - Example of Data Set ......................................... 100

15.......................Example of Height-Weight Curve ............................................... 101

16.......................Height-Weight - Method for Transferring Data ........................... 102

17.......................Actual Weight Form ............................................................. 106-108

18.......................Grazed Class Form ............................................................... 114-115

19.......................Grazed Class Method Photo Guides............................................ 116

20.......................Grazed Class - Example of Data Set............................................ 117

21.......................Grazed Class Height-Weight Curve ............................................ 118

22.......................Landscape Appearance Form ................................................ 123-125
i

PREFACE

DEDICATION

This publication is dedicated to the memory of Kristen R. Eshelman, who

contributed tremendously to its development and preparation. Throughout his career, Kris was instrumental in producing numerous technical

references outlining procedures for rangeland inventory, monitoring, and

the evaluation of rangeland data. Through his efforts, resource specialists

were provided with the tools to improve the public rangelands for the

benefit of rangeland users and the American public.

DEDICATION
iii

PREFACE

I. PREFACE

The intent of this interagency monitoring guide is to provide the basis for consistent, uniform, and standard utilization studies and residual measurements that are economical,

repeatable, statistically reliable, and technically adequate. While this guide is not all inclusive, it does include the primary study methods used across the West. An omission of a

particular sampling method does not mean that the method is not valid in specific locations;

it simply means that it is not widely used or recognized throughout the western states.

(see Section V.E, Other Methods.)

Proper use and management of our rangeland resources has created a demand for uniformity

and consistency in rangeland health measurement methods. As a result of this interest, the

USDI Bureau of Land Management (BLM) and USDA Forest Service met in late 1992 and

agreed to establish an interagency technical team to jointly oversee the development and

publishing of vegetation sampling field guides.

The 13-member team currently includes representatives from the Forest Service, BLM, the

Grazing Land Technology Institute of the Natural Resource Conservation Service (NRCS),

and the Cooperative Extension Service.

The interagency technical team first met in January 1994 to evaluate the existing rangeland

monitoring techniques described in BLM’s Utilization Studies, Technical Reference TR 4400-3.

The team spent 2 years reviewing, modifying, adding to, and eliminating techniques for this

interagency Utilization Studies and Residue Measurements technical reference. Feedback

from numerous reviewers, including field personnel, resulted in further refinements.
1

INTRODUCTION

II. INTRODUCTION

Utilization data and residual measurements are important in evaluating the effects of grazing

and browsing on rangeland. Utilization measures the percentage of annual herbage production that has been removed. It is generally the percentage of available forage (weight or

numbers of plants, twigs, etc.) that has been consumed or destroyed. Utilization is expressed

in terms of the current year’s production removed. Residual measurement is the determination of herbage material or stubble height left. Residual measurements and utilization data

can be used: (1) to identify use patterns, (2) to help establish cause-and-effect interpretations

of range trend data, and (3) to aid in adjusting stocking rates when combined with other

monitoring data.

Permittees, lessees, other rangeland users, and interested publics should be consulted and

encouraged to participate in collecting and analyzing utilization and residual data. Those

individual or groups interested in helping to collect data should be trained in the technique

used in that specific management unit.

This document deals with the collection of utilization data and residual measurements. The

interpretation of this data will be addressed in other documents.

Utilization data and residual measurements should not be used alone to determine stocking

rates. Adjustment in stocking rates should also include trend data, climatic information,

actual use data, and other information.

A. Terms and Concepts

1. Objectives

a Short-term Use of Utilization Data In the short term, utilization data are

considered with actual use and climate data to determine resource use levels

and to identify needed adjustments in management actions. These same data

can be used in the short term as the basis for adjusting grazing use by agreement

or grazing decision.

b Long-term Use of Utilization Data In addition to the above short-term

objectives, utilization data are considered along with other monitoring data to

determine if management actions or practices are achieving management objectives identified in the land-use, coordinated resource management, and activity

plans.

2. Utilization Utilization is the proportion or degree of current year’s forage

production that is consumed or destroyed by animals (including insects). Utilization may refer either to a single plant species, a group of species, or the vegetation

as a whole. Utilization is synonymous with use. This process requires a comparison

of the amount of herbage left compared with the amount of herbage produced

during the year.

3. Seasonal Utilization Seasonal utilization is the amount of utilization that has

occurred before the end of the growing season.
INTRODUCTION

2

4. Residual Measurements Residual measurement is the determination of

herbage material or stubble height left after a grazing or use period. It is independent of the amount of annual production. Management actions based on stubble

height have an impact on plant health and soil and watershed protection because a

specified amount of foliage will be left regardless of the amount of annual production. The important management consideration is to determine the species to

evaluate and the proper use levels that will leave the appropriate residual stubble

height.

5. Removal Versus Residual There are two problems with determining utilization or the amount of annual herbage removed: measuring the amount of total

production for the year and determining the amount of herbage that has been

removed. Measuring the residual plant biomass or stubble height rather than

utilization may be preferable because it is the plant biomass remaining that will

have an important impact on plant health, potential regrowth, and soil and watershed protection.

B. Guidelines The techniques described here are guidelines for establishing and

conducting utilization and residue studies. They are not standards. Utilization and

residue sampling techniques and standards need to be based on management objectives.

Techniques can be modified or adjusted to fit a particular resource situation or management objectives as long as the principles of the technique are maintained. Before a

modified technique is used, it should be reviewed by agency monitoring coordinators,

cooperators, and other qualified individuals. A modified technique should be clearly

identified and labeled as “MODIFIED.” All modifications to transect layout, etc.,

should be clearly documented each time the method is used.

If at all possible, utilization and residue studies should be established not only to

determine the amount of use occurring, but also to determine the agent (livestock,

wildlife, insects, recreation, etc.) causing the use.

C. Location of Sample Sites Utilization and residue studies can be completed anywhere, depending on the objectives. For use pattern mapping, utilization

and residue studies should be collected on enough sites to provide a clear picture of

the use that has occurred.

The site selection process used should be documented. Documentation should include the management objectives, the criteria used for selecting the sites, and the kinds

of comparisons or interpretations expected to be made from them.

Common locations for studies include critical areas and key areas. Some of the site

characteristics and other information that may be considered in the selecting study

sites are:

• Soil

• Vegetation (kinds and distribution of plants)

• Ecological sites

• Seral stage

• Topography

• Location of water, fences, and natural barriers

• Size of pasture
3

INTRODUCTION

• Kind and/or class of forage animals - livestock, wildlife, wild horses, and wild burros

• Habits of the animals, including foraging

• Areas of animal concentration

• Location and extent of critical areas

• Erosion conditions

• Threatened, endangered, and sensitive species - both plant and animal

• Periods of animal use

• Grazing history

• Location of salt, mineral, and protein supplements

• Location of livestock, wildlife, wild horse, and/or wild burro trails

1. Critical Areas Critical areas are areas that should be evaluated separately from

the remainder of a management unit because they contain special or unique

values. Critical areas could include fragile watersheds, sage grouse nesting grounds,

riparian areas, areas of critical environmental concern, etc.

2. Key Areas Key areas are indicator areas that are able to reflect what is happening on a larger area as a result of on-the-ground management actions. A key area

should be a representative sample of a large stratum, such as a pasture, grazing

allotment, wildlife habitat area, herd management area, watershed area, etc.,

depending on the management objectives being addressed by the study. Key areas

represent the “pulse” of the rangeland. Proper selection of key areas requires appropriate stratification. Statistical inference can only be applied to the stratification

unit.

a Selecting Key Areas The most important factors to consider when selecting

key areas are the management objectives found in land use plans, coordinated

resource management plans, and/or activity plans. An interdisciplinary team

should be used to select these areas. In addition, permittees, lessees, and other

interested publics should be invited to participate, as appropriate, in selecting

key areas. Poor information resulting from improper selection of key areas leads

to misguided decisions and improper management.

b Criteria for Selecting Key Areas The following are some criteria that should

be considered in selecting key areas. A key area:

• Should be representative of the stratum in which it is located.

• Should be located within a single ecological site and plant community.

• Should contain the key species where the key species concept is used.

• Should be capable of, and likely to show, a response to management actions.

This response should be indicative of the response that is occurring on the

stratum.

c Number of Key Areas The number of key areas selected to represent a

stratum ideally depends on the size of the stratum and on data needs. However,

the number of areas may ultimately be limited by funding and personnel

constraints.
INTRODUCTION

4

d Objectives Objectives should be developed so that they are specific to the key

area. Monitoring studies can then be designed to determine if these objectives

are being met.

e Mapping Key Areas Key areas should be accurately delineated on aerial

photos and/or maps. Mapping of key areas will provide a permanent record of

their location.

D. Key Species Key species are generally an important component of a plant

community. Key species serve as indicators of change and may or may not be forage

species. More than one key species may be selected for a stratum, depending on

management objectives and data needs. In some cases, problem plants (poisonous,

exotics, etc.) may be selected as key species. Key species may change from season to

season and year to year.

1. Selecting Key Species Selection of key species should be tied directly to

management objectives in land use, coordinated resource management, and activity

plans. The species selected will depend upon the plant species in the present plant

community, the present ecological status, and the potential natural communities

for the specific sites. An interdisciplinary team should be used in selecting key

species to ensure that data needs of the various resources are met. In addition,

interested publics should be invited to participate, as appropriate, in selecting

these species.

2. Considerations in Selecting Key Species The following points should be

considered in selecting key species:

a The forage value of key species may be of secondary or no importance. For

example, watershed protection may require selection of plants as key species

that protect the watershed but are not the best forage species. In some cases,

threatened, endangered, or sensitive species that have no particular forage value

may be selected as key species.

b Any foraging use of the key species on key areas is assumed to reflect foraging

use on the entire stratum. Utilization percentages in this situation are an index

of the use on key species.

c Depending on the selected management strategy and/or periods of use, key

species may be foraged during the growing period, after maturity, or both.

d In areas of yearlong grazing use and in areas where there is more than one use

period, several key species may be selected. For example, on an area with both

spring and summer grazing use, a cool season plant may be the key species

during the spring, while a warm season plant may be the key species during the

summer.

e Selection of several key species may be desirable when adjustments in livestock

grazing use are anticipated. This is especially true if more than one plant

species contributes a major portion of the forage base of the animals using the

area (Smith 1965).
5

INTRODUCTION

3. Key Species on Depleted Rangelands The key species selected should be

present on each study site on which utilization and residue studies are conducted;

however, on depleted rangelands these species may be sparse. In this situation it

may be necessary to conduct monitoring studies on other species. Data gathered

on non-key species must be interpreted on the basis of effects on the establishment

and subsequent response of the key species. It should also be verified that the site

is ecologically capable of producing the key species.

E. Coordination Utilization and residue studies should be planned and implemented on an interdisciplinary basis. Coordination with livestock operators, other

appropriate state and federal agencies, and interested publics is also a crucial factor to

success.

F. Electronic Data Recorders

Electronic data recorders are handheld “computers” that are constructed to withstand

the harsh environmental conditions found in the field. They are used to record monitoring data in a digital format that can be transferred directly to a personal computer

for storage and retrieval. They require minimal maintenance, are generally programmable,

and allow easy data entry using a wand and bar codes.

Recording field data using an electronic data recorder takes approximately the same

amount of time as using printed forms. The advantage with electronic data recorders

is that they improve efficiency by reducing errors associated with entering data into a

computer for analysis. They can also reduce the time needed for data compilation and

summarization.

The cost of electronic data recorders and computer software programs is considerable

and should be evaluated prior to purchase. It is also important to have good computer

support assistance available to help users in operating, downloading, and troubleshooting

electronic data recorders, especially during the initial use period.
INTRODUCTION

6
7

STUDY DESIGN AND ANALYSIS

III. STUDY DESIGN AND ANALYSIS

The rangeland monitoring methods described in Section V have a number of common

elements. Those that relate to permanently marking and documenting the study location

are described in detail below.

Also discussed in this section are statistical considerations (target populations, random

sampling, systematic sampling, confidence intervals, etc.) and other important factors (properly identifying plant species and training people so they follow the correct procedures).

It is important to read this chapter before referring to the specific methods described in

Section V, since the material covered here will not be repeated for each of them.

• Permanently Marking the Study Location Permanently mark the location of each study by

means of a reference post (steel post) placed about 100 feet from the actual study location.

Record the bearing and distance from the post to the study location. An alternative is to

select a reference point, such as a prominent natural or manmade feature, and record the

bearing and distance from that point to the study location. If a post is used, it should be

tagged to indicate that it marks the location of a monitoring study and should not be

disturbed.

Permanently mark the study location itself by driving angle iron stakes into the ground at

randomly selected starting points. The baseline technique requires that both ends of the

baseline be permanently staked. If the linear technique is used, only the beginning point

of the study needs to be permanently staked. Establish the study according to the directions found in Section III.A.2 beginning on the next page.

Paint the study location stake with brightly colored permanent spray paint (yellow or

orange) to aid in relocation. Repaint this stake when subsequent readings are made.

• Study Documentation Document the study and transect locations, number of transects,

starting points, bearings, length, distance between transects, number of observation points,

sampling interval, and other pertinent information concerning a study on the Study

Location and Documentation Data form (see Appendix A). Plot the precise location of

the studies on detailed maps and/or aerial photos.

For transects that use a baseline technique, record the location of each transect or quadrat

along the baseline and the direction (left or right). Be sure to document the exact location of the study and the directions for relocating. For example: 1.2 miles from the allotment boundary fence on the Old County Line Road. The reference post is on the south side of

the road, 50 feet from the road.

A. Planning the Study Proper planning is by far the most important part of a

utilization or residue study. Much wasted time and effort can be avoided by proper

planning. A few important considerations are discussed below. The reader should

refer to the Technical Reference, Measuring & Monitoring Plant Populations, for a more

complete discussion of these important steps.

1. Identify Objectives Based on land use and activity plans, identify management

objectives appropriate for the area to be monitored. The intent is to evaluate the
STUDY DESIGN AND ANALYSIS

8

effects of management actions on achieving management objectives by collecting

utilization or residual data.

2. Design the Study The number of points, quadrats, or transects (sample size)

needed depends on the monitoring objectives and the efficiency of the sampling

design. It should be known before beginning the study how the data will be analyzed. The frequency of data collection (e.g., every year, every other year, etc.) and

data sheet design should be determined before studies are implemented. The

sample data sheets included with each method (following the narrative) are only

examples of data forms. Field offices have the option to modify these forms or

develop their own.

All methods described in this document can be established using either the linear

or baseline design.

a Linear This study design samples a management units or study site in a straight

line (Figure 1). Randomly select the beginning point of the transect within the

management units or study site. The transect site can be permanently marked

with a transect location stake, if needed. Randomly determine the transect

bearing and select a prominent distant landmark such as a peak, rocky point,

etc., that can be used as the transect bearing point. Utilization and residue

readings are taken at a specified interval (paced or measured) along the transect

bearing. If the examiner is unable to collect an adequate sample with this

transect before leaving the study site, additional transects can be run from the

transect location stake at different bearings.
9

STUDY DESIGN AND ANALYSIS

Figure 1. Study layout for the linear technique.

Transect Bearing Stake

Study Location Stake

End Point of Transect

100-Meter Tape

Midpoint of Transect

Beginning Point of Transect

Observation

Points
STUDY DESIGN AND ANALYSIS

10

b Baseline A baseline is established by stretching a tape measure of any desired

length between two stakes (Figure 2). For an extremely long baseline, intermediate stakes can be used to ensure proper alignment. It is recommended that

metric measurement be used. Individual transects are then run perpendicular to

the baseline at random locations along the tape. Transects can all be run in the

same direction, in which case the baseline forms one of the outer boundaries of

the sampled area, or in two directions, in which case the baseline runs through

the center of the sampled area. If transects are run in two directions, the direction for each individual transect should be determined randomly. (Directions

on the use of random number tables and random number generators are given

in Appendix F.) Observation points are spaced at specified distances along the

transect. This study design is intended to randomly sample a specified area.

The area to be sampled can be expanded as necessary by lengthening the

baseline and/or increasing the length between sampling points.

B. Statistical Considerations

1. Target Population Sample sites are selected (subjectively) that hopefully

reflect what is happening on a larger area. These may be study sites that are

considered to be representative of a larger area (such as a pasture) or may be

critical areas such as sites where endangered species occur (see Section II.C).

Utilization and residue studies are then located on these sites. Since study sites are

subjectively selected, no valid statistical projections to an entire management area

are possible. Therefore, careful consideration and good professional judgement

must be used in selecting study sites to ensure the validity of any conclusions reached.

a Although it would be convenient to make inferences regarding larger areas from

sampling study sites, there is no way this can be done in the statistical sense

because these study sites have been chosen subjectively.

b For this reason it is important to develop objectives that are specific to study

sites. It is equally important to make it clear what actions will be taken based

on what happens on the study sites.

c It is also important to base objectives and management actions on each study

site separately. Values from study sites from different strata should never be averaged.

d From a sampling perspective, it is the study sites that constitutes the target

population. The collection of all possible sampling units that could be placed in

the study sites is the target population.

2. Random Sampling Critical to valid monitoring study design is that the sample

be drawn randomly from the population of interest. There are several methods of

random sampling, several of which are discussed briefly below, but the important

point is that all of the statistical analysis techniques available are based on knowing

the probability of selecting a particular sampling unit. If some type of random

selection of sampling units is not incorporated into the study design, the probability of selection cannot be determined and no statistical inferences can be made

about the population. (Directions on the use of random number tables and random number generators are given in Appendix F.)
11

STUDY DESIGN AND ANALYSIS

Figure 2. Study layout for the baseline technique.

Transect 1

Transect 2

Transect 3

∆

∆

Baseline End Point Stake

100-Meter Baseline Tape

Study Layout

∆

∆

Study Location Stake

Baseline Beginning Point Stake
STUDY DESIGN AND ANALYSIS

12

3. Systematic Sampling Systematic sampling is very common in utilization and

residue studies. The collection of utilization or residual data along a transect at

specified intervals is an example of systematic sampling. The starting point of a

transect must be randomly selected. If the interval between observations is 5 paces

(meters or feet can used), a number between 0 and 4 is randomly selected to

represent the distance from the reference point or baseline to start making observations. Additional observations are made at 5-pace intervals from this starting

point. Thus, if 10 observations are to be made at 5-pace intervals and the randomly selected number between 0 and 4 is 2, then the first observation is made at

2 paces and the remaining observations occur at 7, 12, 17, 22, 27, 32, 37, 42, and

47 paces along the transect.

Strictly speaking, systematic sampling is analogous to simple random sampling only

when the population being sampled is in random order (see, for example, Williams

1978). Many natural populations of both plants and animals exhibit an aggregated

(also called clumped) spatial distribution pattern. This means that nearby units

tend to be similar to (correlated with) each other. If, in a systematic sample, the

sampling units are spaced far enough apart to reduce this correlation, the systematic sample will tend to furnish a better average and smaller standard error than is

the case with a random sample, because with a completely random sample one is

more likely to end up with at least some sampling units close together (see Milne

1959 and the discussion of sampling an ordered population in Scheaffer et al.

1979).

4. Sampling Versus Nonsampling Errors In any monitoring study, it pays to

keep the error rate as low as possible. Errors can be separated into sampling errors

and nonsampling errors.

a Sampling Errors Sampling errors arise from chance variation; they do not

result from “mistakes” such as misidentifying a species. They occur when the

sample does not reflect the true population. The magnitude of sampling errors

can be measured.

b Nonsampling Errors Nonsampling errors are “mistakes” that cannot be

measured.

Examples of nonsampling errors:

• Using biased selection rules, such as selecting “representative samples” by

subjectively locating sampling units or substituting sampling units that are

“easier” to measure.

• Sloppy field work.

• Transcription and recording errors.

• Incorrect or inconsistent species identification.

To minimizing nonsampling errors:

• When different personnel are used, conduct rigorous training and testing to

ensure consistency in measurement and estimation.
13

STUDY DESIGN AND ANALYSIS

• Design field forms that are easy to use and not confusing to data transcribers.

Double- or triple-check all data entered into computer programs to ensure

the numbers are correct.

5. Confidence Interval In rangeland monitoring, the true population total (or any

other true population parameter) can never be determined. The best way to judge

how well a sample estimates the true population total is by calculating a confidence

interval. The confidence interval is a range of values that is expected to include the

true population size (or any other parameter of interest, often an average) a given

percentage of the time (Krebs 1989). Confidence intervals are the principal means

of analyzing utilization data. For instructions in calculating confidence intervals, see

the Technical Reference, Measuring & Monitoring Plant Populations.

6. Interspersion One of the most important considerations of sampling is good

interspersion of sampling units throughout the area to be sampled (the target

population). The basic goal should be to have sampling units as well interspersed

throughout the area of the target population as possible. The practice of placing

all of the sampling units, whether they be quadrats or points, along a single transect

or even a few transects should be avoided. Arranging sampling units in this manner results in poor interspersion of sampling units and makes it unlikely that the

sample will provide a representative sample of the target population. This is true

even if the single transect or few transects are randomly located.

7. Pilot Studies In several places in this chapter, the need to conduct pilot studies

has been stressed. The principal purpose of pilot studies is to determine the

sample size necessary to estimate vegetation characteristics of interest (e.g., utilization level, stubble height, biomass) with a given level of precision. Pilot sampling

allows the examiner to obtain stable estimates of the population average and the

population standard deviation. This is accomplished by using standard deviation

calculations and sequential sampling as described below.

a Standard Deviation Calculations The following shows how to calculate the

standard deviation for utilization on sideoats grama. The standard deviation is

calculated as follows:

where:

S = standard deviation

X = number of plants

X = the mean or average % utilization or residual measurement

n = the number of samples (observation points in this example)

Utilization Squared

estimates Deviation Deviation

(X - X) (X - X)2

49 49-39 = 10 100

37 37-39 = -2 4

39 39-39 = 0 0

49 49-39 = 10 100

22 22-39 = -17 289

X= 196/5 = 39 493

(X1 - X)2 + (X2 - X)2 + . . . + (Xn - X)2 (X - X)2

n -1

S = or S =

n -1
STUDY DESIGN AND ANALYSIS

14

b Sequential Sampling The estimate of the standard deviation derived through

pilot sampling is one of the values used to calculate sample size, whether one

uses the formulas given in the Technical Reference, Measuring & Monitoring

Plant Populations, or a computer program. Sequential sampling helps determine

whether the examiner has taken a large enough pilot sample to use the standard

deviation from the pilot sample to calculate sample size. The process is

accomplished as follows.

Gather pilot sampling data using some arbitrarily selected sample size. Calculate

the average and standard deviation for the first two sampling units (for the

methods described in this Technical Reference these are either individual plants,

quadrats, or observation points), calculate it again after putting in the next sampling unit value, and continue these iterative calculations after the addition of

each sampling unit value to the sample. This will generate a running average and

standard deviation. Look at the four columns of numbers on the left of Figure 3.

Figure 3. Example of a sequential sampling graph. The running average and standard deviation are plotted

for sample sizes up to n=50. Data are utilization percentages calculated using the paired plot method. Actual

values are shown on the left. As this graph shows, both the average and the standard deviation have

stabilized by about n=23. The standard deviation at n=23 (9.23) can be plugged into a sample-size formula

to determine the sample size needed for estimating the utilization with the precision specified.

(X - X)2

n -1

S = = = = = 11.10 493

5 -1

493 123

4

1 0

20

40

60

5 10 15 20 25

Sample Size

Average

SD

Example of a sequential sampling graph

% Utilization

30 35 40 45 50

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

32

33

34

35

36

37

38

39

40

41

42

43

44

45

46

47

48

49

50

%

Utilization

49

37

39

49

22

38

41

42

34

33

41

49

40

52

34

47

56

35

43

45

25

61

35

33

40

32

46

32

42

36

28

32

34

37

42

45

39

43

37

13

34

39

41

48

45

49

34

32

43

49

Average

49.00

43.00

41.87

43.50

39.20

39.00

39.29

39.63

39.00

38.40

38.64

39.50

39.54

40.43

40.00

40.44

41.35

41.00

41.11

41.30

40.52

41.45

41.17

40.83

41.16

40.81

41.00

40.68

40.72

40.57

40.16

39.91

39.73

39.65

39.71

39.86

39.84

39.92

39.85

39.18

39.05

39.05

39.09

39.30

39.42

39.63

39.51

39.35

39.43

39.62

 SD

8.48

5.43

6.40

11.10

9.94

9.11

8.48

8.15

7.92

7.55

7.80

7.47

7.91

7.80

7.74

8.39

8.27

8.05

7.89

8.47

9.35

9.23

9.18

9.14

9.13

9.01

9.00

8.84

8.73

8.88

8.85

8.77

8.65

8.53

8.46

8.34

8.24

8.15

9.09

9.01

8.90

8.80

8.80

8.74

8.76

8.70

8.68

8.60

8.62
15

STUDY DESIGN AND ANALYSIS

Plot on graph paper (or use a computer program to plot) the sample size versus

the average and standard deviation. Look for curves smoothing out. In the

example shown in Figure 3, the curves smooth out after n = 21-25. The decision

to stop sampling is a subjective one. There are no hard-and-fast rules.

A computer is valuable for creating sequential sampling graphs. Spreadsheet

programs such as Lotus 1-2-3 allow for both entering the data in a form that

can be analyzed later and simultaneously creating a sequential sampling graph

of the running average and standard deviation. This also allows one to look at

several random sequences of the data before deciding on the number of sampling

units to measure.

Use the sequential sampling method to determine what sample size not to use

(don’t use the sample size below the point where the running average and

standard deviation have not stabilized). Plug the final average and standard

deviation information into the appropriate sample size equation to determine

the optimum sample size.

c Sample Size Determination An adequate sample is vital to the success of any

successful monitoring effort. Adequacy relates to the ability of the observer to

evaluate whether the management objective has been achieved. Management

objectives related to utilization, for example, will state maximum allowable

levels of utilization on key species. Thus, the management objective might be to

allow utilization of no more than 30 percent on key species X. Because the

utilization of all plants of key species X cannot be measured, a sample must be

taken. Depending upon how large a sample is taken and how variable the

utilization is in the area sampled, the estimate from the sample may be very

close to the true value or very far from it. The confidence interval in the former

case will be narrow; in the latter case it will be wide.

The first step in determining sample size is to take the management objective

and frame a corresponding monitoring objective. This monitoring objective

specifies how precise an estimate is needed to assess whether the management

objective has been met. In the example introduced above, our management

objective is as follows:

Allow no more than 30 percent utilization of Key Species X in study site Y in any year.

The corresponding monitoring objective might be:

Estimate the utilization on Key Species X in study site Y every year. Ensure, with 95

percent confidence, that the estimate is within 5 percent (absolute) of the true

utilization value.

Note that this monitoring objective has specified a 95 percent confidence

interval size of ±5 percent for the estimate. This means that if the average from

the sample is 25 percent utilization on the key species, the examiner can be 95

percent confident that the true amount of utilization on the key species

throughout the area sampled is somewhere between 20 percent and 30 percent.

Once the monitoring objective has been developed and there is a good estimate

of the standard deviation derived from sequential sampling, the sample size
STUDY DESIGN AND ANALYSIS

16

needed to meet this monitoring objective can be calculated. Formulas for

calculating sample sizes are given in the Technical Reference, Measuring &

Monitoring Plant Populations. Because these formulas are rather unwieldy, you

may choose to use a computer program. There are at least two computer

programs that will calculate the sample size necessary to estimate a single

population average with a given level of precision. These are the program

DESIGN (by SYSTAT) and PC-SIZE: CONSULTANT. Both of these were

developed by Gerard E. Dallal, but the latter is a much better value, since it is

shareware (the author asks for a fee of $15.00 if the user finds the program to be

useful). The program is available via the World Wide Web at the following address:

http://www.coast.net/SimTel/SimTel/

Once at the homepage, change to the directory msdos/statstic/ and download

the file st-size.zip. Unzip the file using the shareware program PKUNZIP.

Executable files and documentation are included.

Consult the Technical Reference, Measuring & Monitoring Plant Populations, for

more information on calculating sample size.

8. Graphical Display of Data The use of graphs, both to initially explore the

quality of the monitoring data collected and to display the results of the data

analysis, is important to designing and implementing monitoring studies. See the

Technical Reference, Measuring & Monitoring Plant Populations, for descriptions of

these graphs, along with examples.

a Graphs to Examine Study Data Prior to Analysis The best of these graphs

plot each data point. These graphs can help determine whether the data meet

the assumptions of parametric statistics, or whether the data set contains outliers (data with values much lower or much higher than most of the rest of the

data — as might occur if one made a mistake in measuring or recording). Normal probability plots and box plots are two of the most useful types for this

purpose. For more information, see the Technical Reference, Measuring &

Monitoring Plant Populations.

b Graphs to Display the Results of Data Analysis Rather than displaying

each data point, these graphs display summary statistics (e.g., averages, totals, or

proportions). When these summary statistics are graphed, error bars must be

used to display the precision of estimates. Because it is the true parameter

(average or median) that is of interest, confidence intervals should be used as

error bars. Types of graphs include:

(1) Bar charts of averages or medians with confidence intervals.

(2) Graphs of summary statistics plotted as points, with error bars.

(3) Box plots with “notches” for error bars.

9. Data Analysis and Interpretation Utilization and residue studies do not

compare data differences between years, so significance tests are not ordinarily

employed. The appropriate analysis of utilization data depends upon whether

management objectives are written based on the average, median, or other
17

STUDY DESIGN AND ANALYSIS

percentile utilization. Confidence intervals (for a selected level of confidence) are

then calculated around this average, median, or other percentile.

Confidence intervals are set around an estimated average value to indicate that the

true average of the population will occur within those limits a specified percentage

of the time. The sample average is the best estimate of the population average

available if it has been measured in an unbiased way. (The confidence interval

does not account for bias, which arises from error or incompetence.) The width of

the confidence interval is determined by the variability of the measurements.

For many utilization objectives, the median is a better measure of central tendency

than the average. This is particularly true for stubble height data, where the

average should never be used as the measure of central tendency. Using the median ensures that at least half of the plants measured meet or exceed whatever

objective has been set. Because utilization data are often not normally distributed,

using the average will not guarantee this. Just as with the average, confidence

intervals for the median must be calculated.

Another alternative is to base the management objective on a percentile other than

the median (the median is the 50th percentile). For example, with stubble height

data the objective could be that at least 60 percent of the plants be taller than a

selected threshold, say 4 inches. A confidence interval would then be constructed

around the 60th percentile of the sample data and the lower bound of the interval

used as the conservative estimate of the true 60th percentile. For example, the

sample 60th percentile may be 4.5 inches and the 95 percent confidence interval

for the 60th percentile may be 3.75 inches to 5.25 inches. The 3.75-inch figure

would be used as the conservative estimate of the 60th percentile.

C. Collecting Utilization Data and Residue Measurements

1. Transects Utilization and residue studies should be located within representative

portions of the management unit (see Section II.C).

a Starting Point The starting point of a transect should be randomly located.

b Bearing or Direction The bearing or direction of the transect from the starting point should either be set by compass or directed toward a permanent,

clearly defined, highly visible natural feature. Straight-line transects should

cross drainages, if possible, in order to obtain a representative sample. Where

uplands and riparian areas have significantly different levels of utilization, they

should not be included within the same study site since extremes in percent

utilization on one portion of the site may mask extremes on other portions of

the site. See Section III.A.2 for a discussion on establishing a baseline technique

for collecting utilization data.

2. Observations and Quadrats

a Sampling Interval Observations or quadrats are located at constant intervals

along transects. If the key species or other selected species is not present at the

selected interval, relocate the observation point or quadrat to the nearest
STUDY DESIGN AND ANALYSIS

18

individual of that species along each transect line. The next interval along each

transect is measured from this relocated point.

b Observation Sites Exercise care to ensure that observation sites do not overlap.

c Quadrat Size If quadrats are used, ensure that all quadrats on a transect are of

the same size so that the individual quadrat percentages can be added together

and averaged.

d Number of Observations or Quadrats Use pilot transects to determine the

number of observation points or quadrats. Inaccuracies produced by estimating

utilization tend to be reduced by using a larger number of observations or

quadrats.

e Statistical Analysis Run statistical analysis on pilot (sample) transects to

assure adequate sample size and required precision (see Section III.B.7).

f Marking Locations Record the location of each transect on a map or aerial photo.

3. Frequency of Studies Utilization and residue studies may be conducted every

year or as often as needed after the growing season to satisfy data requirements for

grazing allotment, wildlife habitat area, herd management area, watershed area, or

other designated management area evaluations. In some cases, utilization and

residue studies are started upon initiation of intensive management and continued

annually through one complete cycle of a grazing system, or for as long as necessary. It may be necessary to conduct utilization and residue studies annually until

management objectives are achieved and maintained. Utilization and residue

studies may also be conducted at periodic intervals in sequence with grazing

treatments. For example, utilization and residue studies on individual pastures

could be conducted once every three years on a three pasture grazing system and

once every five years on a five-pasture grazing system. Where studies are conducted only once during each grazing cycle, they should be conducted at the same

point in each cycle so that the data will be comparable.

4. Timing of Studies Utilization studies are conducted at the end of the growing

period within pastures or management units. Seasonal utilization studies are

generally conducted at the end of each period of use within pastures or management units. They may also be conducted at any time during the period of use.

Where livestock, wildlife, wild horses, and/or wild burros are present, it may be

necessary to conduct seasonal utilization studies both before and after discrete

periods of use by these animals to estimate the percent utilization by kind of

animal. Where regrowth may occur, seasonal utilization studies should be conducted as soon as possible following the end of the period of use. Utilization

studies on browse species must be conducted before new twig growth occurs to

obtain accurate measurements or observations of past use.

5. Documentation Utilization data are recorded on appropriate forms. Forms for

the methods described in this Technical Reference are included in the section

describing the method. Close-up and/or general view photographs may be used

with any of the methods (see Section V.A in the Interagency Technical Reference,
19

STUDY DESIGN AND ANALYSIS

Sampling Vegetation Attributes). File the forms, photographs, and any other pertinent

information in the monitoring file or as otherwise prescribed.

6. Interpreting Utilization and Residue Data

a Utilization is an important factor that can bring about changes in soil, water,

animal, and vegetation resources. The impact that a specific intensity of use has

on a plant species is highly variable, depending on past and present use, period

of use, duration of use, interspecies competition, weather, availability of soil

moisture for regrowth, and how these factors interact. Utilization and residue

data can be used alone to determine when livestock should be moved within a

grazing allotment and to identify livestock distribution problems. In combination with actual use and climatic data, utilization and residue measurements and

utilization pattern mapping are useful for estimating proper stocking levels

under current management. Utilization and residue studies are also helpful in

identifying key, critical, and problem areas, and in identifying range improvements

needed to improve livestock distribution.

b When interpreting utilization and residue data, it is important to consider the

climatic conditions that have occurred during the growing season. Light grazing

use during a drought year can appear to be the same as heavy use during a

normal or above-average precipitation year.

c The reaction that plants have to different levels of utilization can depend on

past conditions and use. Plants that have been rested for a short time, even

during a drought period, can deal with heavier use better than plants that have

been previously stressed by heavy use.

d The relationship between the level of utilization and the overall condition of

the plant is not always clear. Climatic conditions, composition of adjacent

vegetation, season of use and other variables must be taken into account in

interpreting utilization and residual studies (Sharp et al. 1994).

D. Other Important Considerations Consistency is important in measuring

or estimating utilization.

1. Availability The measurement of forage utilization should be based on the

availability of the vegetation. Vegetation that is beyond the reach of grazing

animals because of obstructions such as brush or height should not be considered

in determining the level of utilization.

2. Plant Species Identification It is important that the plant species be properly

identified when conducting utilization and residue studies. In some cases, it may

be helpful to include pressed plant specimens, photographs, or other aids used for

species identification in the study file. If data are collected prior to positive species

identification, examiners should collect plant specimens for later verification.

3. Utilization Levels “Desired,” or “target,” utilization levels for specific areas of

rangeland are reflected in the management objectives of land-use, coordinated

resource management, and activity plans. These levels refer to the desired utilization of key plant species or several plant species within a study site. The desired
STUDY DESIGN AND ANALYSIS

20

percent utilization for a plant species can vary from plant community to plant

community. It can also vary depending on period of use, previous intensity of use,

and growth conditions or vigor of the plants. Other demands, such as concurrent

or seasonal use by more than one animal species, may also be important in selecting the desired utilization level. Percent utilization is expressed in terms of plant

species and locality.

4. Plants Used to Determine Utilization Generally, only plants of the selected

key species are used in utilization and residue studies. This does not preclude

sampling plants of other species if these additional data are needed.

5. Plant Height-Weight Relationship Weight is not evenly distributed

throughout the height or length of plants of any given species. For most rangeland

plants, a high percentage of the weight is in the basal portion of the plant or twig

where growth is thicker or more dense. A low percentage of plant weight is in the

upper portion where growth is tapered or less dense. When estimating percent

utilization, adjust for differences in weight by height or length. Weight distribution in relation to height is reasonably constant among individuals of the same

plant species.

6. Utilization Cages Utilization cages are used to provide a guide to utilization

and production. Grasses, forbs, and shrubs can be protected from foraging with

these cages. Utilization cages should not appreciably disrupt normal vegetation

growth. The cages must be moved each year at the beginning of the foraging

period. This will allow for comparison of rangelands inside and outside the protected plots. These cages can be used to show utilization rates to all interested

parties. They can also be used to collect information showing forage production

fluctuations due to yearly climatic changes (see Section V.C.1 and Appendix E).

7. Regrowth Plant regrowth occurs following an interruption in growth by grazing,

fire, etc., as well as growth that occurs in response to favorable weather events

following the normal growing season. When animals use the same area more than

once a year and plant regrowth may occur or has occurred, seasonal utilization is

based on the amount of growth available at the time the data are collected. The

percent seasonal utilization after each period of use represents only the amount of

available growth that has been utilized up to the time the studies are conducted.

Seasonal utilization percentages recorded for various periods of use during a year

cannot simply be added together to get total utilization for the year. In other

words, 30 percent seasonal utilization of 6 inches of plant growth available in the

spring, and 30 percent seasonal utilization of 12 inches of plant growth available in

the fall, do not add up to 60 percent utilization for the year.

8. Study Site Assessment The effectiveness of ecosystem management may

require the collection of utilization data on more than the key livestock forage

species. Each site selected for completion of utilization and residue studies should

be evaluated to determine what plant species are being utilized. It is important to

consider use by all animals: livestock, wildlife, and insects. Nonconsumptive uses

such as trampling and damage from recreational activities should also be analyzed.

The length of the growing season can affect the species to be evaluated. It is

important to determine whether a study site supports both cool and warm season
21

STUDY DESIGN AND ANALYSIS

species. It may be necessary to collect utilization data on both cool season and

warm season species at different times during the year to get a complete picture of

grazing impacts on ecosystem management.

9. Training The objective of training is to provide examiners with the skills needed

to implement utilization and residue studies and collect reliable, unbiased, and

consistent data. Examiners should understand procedures for data collection, data

recording, study location documentation, and data analysis, interpretation, and

evaluation. Examiners should also be taught the importance of uniformity, accuracy, and reliability in collecting monitoring data. Examiners must be able to

accurately identify plant species.

Training should occur in the field by qualified personnel to ensure that examiners

are familiar with the equipment and supplies and that detailed procedural

instructions are thoroughly demonstrated and understood.

As a follow-up to the training, utilization data collected should be examined early

in the effort to ensure that the data are properly collected and recorded.

Periodic review and/or recalibration during the field season may be necessary for

maintaining consistency among examiners because of progressive phenological

changes. Review and recalibration during each field season are especially important

where data collection methods require estimates rather than direct measurements.
STUDY DESIGN AND ANALYSIS

22
23

UTILIZATION PATTERNS (USE ZONES)

IV. UTILIZATION PATTERNS (USE ZONES)

Rangelands include various combinations of range sites and vegetation types on which

utilization is seldom uniform. Utilization patterns (use zones) may result from a number of

factors that either alone or in combination cause foraging animals to concentrate in specific

areas or to spread out over large areas.

For mapping use zones, any number of use classes can be identified based on need. The seven

class delineation described in the Keys Species Method (0-5%, 6-20%, 21-40%, 41-60%, 61-80%,

81-94%, 95-100%) as well as a three class delineation (0-40%, 41-60%, 61-100%) are often used.

A. Base Map for Displaying Utilization Patterns Aerial photographs,

ortho-photo quads, or topographic maps should be used for mapping utilization

patterns. It is important that the selected base show ecological sites or vegetation

types and physical features such as fences, water, and roads. If utilization patterns are

mapped on mylar overlayed on a base map, the patterns can easily be compared

between years. Geographic information systems can also be used for this purpose.

B. Mapping Utilization Patterns Utilization patterns may be mapped for

wildlife, wild horses, or wild burros, as well as for livestock, following discrete use

periods by these animals.

The first step in conducting utilization studies is preparing a map that shows the

forage utilization patterns in a pasture or management unit. Mapping utilization

patterns involves traversing the management unit or pasture to obtain a general concept of these patterns. Mapping proceeds as the pasture is traversed. When another

use zone is observed, the approximate boundary of the zone is recorded on the map.

Areas that do not have any of the key species should also be delineated. Information

that should be recorded for each traversed use zone include the name(s) of the key or

important plant species grazed. Features such as topography, rockiness, size of the

area, location of salt, and distance from water all affect foraging habits of different

kinds of animals. Recording signs of use by wildlife, wild horses and burros, or livestock in an area can be useful for determining the kinds of large herbivores using an

area. Unused areas suitable for grazing and areas of animal concentration should be

delineated to help identify range improvements needed to change grazing use distribution. Mapped utilization patterns can be used to stratify a management unit or pasture and to select key areas. Permittees, lessees, other rangeland users, and interested

parties should be consulted and encouraged to participate in the mapping of utilization

patterns.

Documentation of livestock and wildlife use during a use period is beneficial for

observing use patterns as they develop.

The standard time for preparing use mapping and completing utilization measurement

should be at the end of the growing season. Seasonal utilization can be collected at

the end of a use period. This timing would indicate the amount of use at a particular

time due to a certain stocking rate and mix of animals. It would also show the

cumulative effect of grazing on plants through a sequence of growth stages.
UTILIZATION PATTERNS (USE ZONES)

24

Use patterns usually do not vary significantly from year to year unless there has been

some modification in the number of days of use by animals, season of use, water

locations, fences, or salt locations; unauthorized use; or unusual weather. It is not

necessary to map a pasture or use area every year unless a management change or a

significant change in the number of animals grazing in an area has occurred, e.g., a

livestock adjustment or wild horse removal. Use pattern mapping is also essential for

tracking the progress and impacts of range improvements and management changes.
25

METHODS—BROWSE REMOVAL—Twig Length Measurement

V. METHODS

A. Browse Removal Methods

1. Twig Length Measurement Method With the Twig Length Measurement

Method, utilization is determined by measuring twigs on 25 to 50 browse plants

after full annual growth has occurred and again after the period of use. The

difference between the two measurements is an estimate of the amount of browse

that has been utilized. Separate transects are run for different browse species.

This method is used primarily on wildlife winter range.

a Areas of Use This method of determining utilization is restricted to use on

browse species that clearly exhibit annual twig growth, such as bitterbrush and

mountain mahogany.

b Advantages and Limitations

(1) Percent utilization determined by measurement is more accurate than

utilization determined by ocular observation. This method is useful in

determining the amount of use made on browse plants by livestock and the

amount of use made on the same browse plants by wildlife, wild horses,

and/or wild burros. The degree of direct forage competition among different kinds of animals can be determined where there are discrete periods of

use by different animals. Growth and use indexes can also be determined.

(2) Good utilization estimates can be obtained with this method even though

twig volume is not uniformly distributed along the length of twigs. The

results will vary with species due to twig growth characteristics.

(3) The method is not reliable on species that do not clearly exhibit annual

twig growth, such as sagebrush and serviceberry. It is also not reliable in

areas of the Southwest where annual twig growth may be masked by

almost continuous growth or erratic seasonal growth after rains.

(4) The time and expense needed for gathering data are doubled because the

measurements must be made twice a year.

c Equipment

• Study Location and Documentation Data form (see Appendix A)

• Twig Length Measurement form (see Illustration 1)

• Twenty-five to 50 numbered metal tags

• Roll of soft copper or aluminum wire

• 12-inch ruler or metric equivalent

• Compass

• Steel post

• Post driver
METHODS—BROWSE REMOVAL—Twig Length Measurement

26

d Training This method does not require intensive training for field application.

Examiners must be able to identify the plant species and recognize annual twig

growth on the selected key species (see Section III.D.9).

e Establishing Studies Careful establishment of studies is a critical element in

obtaining meaningful data. Select key species and determine the number,

length, and location of the transects (see Section III.B.7).

(1) Collect data using several pilot transects to determine the number of

transects needed and the number of observations to be made on each

transect. These data are needed to determine if a statistically valid sample

has been collected (see Section III.B.7).

(2) In mixed stands of key browse, such as bitterbrush and mountain mahogany, establish separate transects for each species.

(3) At the beginning of each study, determine the transect bearing and distance

between observation points. Select a prominent distant landmark such as a

large tree, rocky point, etc., that can be used as the transect bearing point.

(4) Plot the transects on detailed management unit maps and/or aerial photos

(see beginning of Section III).

(5) Permanently mark the location of each study with a reference post and

study location stake (see beginning of Section III).

(6) Number studies for proper identification to ensure that the data collected

can be positively associated with specific studies on the ground (see Appendix B).

(7) Document the location and other pertinent information concerning the

study on the Study Location and Documentation Data form (see beginning

of Section III and Appendix A).

f Sampling Process After examiners are trained and are confident in their

ability to recognize annual twig growth on the key species, proceed with the

collection of utilization data.

(1) Tag plants of only one species per transect.

(2) Tag 25 to 50 plants of the selected key species on, each transect. Based on

the analysis of past years’ data, additional numbers of plants can be tagged

to improve the precision of the estimate.

(3) Objectively tag plants along the transect. The first tagged plant should be a

minimum of 10 paces from the beginning point of the transect along the

transect bearing. The distance between tagged plants, thereafter, should

depend on the length of the transect. Be sure to document the number of

paces on the study location form.
27

METHODS—BROWSE REMOVAL—Twig Length Measurement

(4) At the end of each pacing interval, select and tag the closest plant of the

key species within a 180-degree zone ahead of the examiner. (See Appendix C

for a schematic of the 180-degree selection zone.)

(5) Using soft copper or aluminum wire, attach a numbered metal tag to an

individual branch that has a minimum of 10 twigs with new growth. The

wire should be loosely attached on the branch to allow for future growth.

Only one tag per plant is needed.

(6) Estimate the percent use that has already occurred and record on the Twig

Length Measurement form (see Illustration 1).

(7) Measure the length of current growth (to the nearest 1/2 inch or nearest

centimeter) on each twig from the point of tag attachment to the end of

the branch. Record the data on the Twig Length Measurement form

(see Illustration 1).

(a) Make the first measurements after plants of the selected key species

have attained full annual growth.

(b) Make subsequent measurements after the period of use.

(8) Face the transect bearing point and begin the next pacing interval from the

last tagged plant.

g Calculations Calculations can be made on the back of Twig Length Measurement

form (see Illustration 1).

(1) Average estimated utilization prior to completion of full annual growth is

the utilization that has occurred up to the time the first measurements are

taken. Determine this utilization percentage by totaling the estimated

percent utilization for the individual plants and dividing the total by the

number of tagged plants.

Total estimated % utilization Average estimated use

for the individual plants = prior to completion

Number of tagged plants of full annual growth

(2) Percent utilization can be calculated as follows:

(a) Total the twig measurements made after completion of full growth for

each tagged plant.

(b) Total the twig measurement made after the period of use for each

tagged plant.

(c) Calculate percent utilization of individual tagged plants as follows:

Total twig length by plant Total twig length by

after full annual growth - plant after period of use x 100 = Percent

Total twig length by plants after full annual growth utilization
METHODS—BROWSE REMOVAL—Twig Length Measurement

28

(d) Calculate the average percent utilization for the key species on the

transect by totaling the percent utilization for the individual tagged

plants and dividing the total by the number of tagged plants. The

average percent utilization may also be calculated as follows:

Total twig length for all tagged Total twig length for all Measured

 plants after full annual growth - plants after period of use x 100 = percent

Total twig length for all tagged plants after full annual growth utilization

(e) Determine the total percent utilization by adding the average estimated utilization prior to completion of full annual growth and the

average percent utilization for the period(s) of use.

Average estimate used prior to Measured percent

completion of full annual growth + utilization = Total percent

(3) Growth index

(a) The growth index is the average twig length for all tagged plants as

determined from the measurements obtained after completion of full

annual growth. This index can be used to compare the amounts of

growth that occur in different years and as an indication of species

vigor.

(b) Calculate the growth index as follows:

Total twig length for all tagged plants

after full annual growth = Growth index

Number of twigs measured (Average twig length)

(c) If use occurred on the plants prior to measurement after completion of

full annual growth, adjust the growth index to account for this use as

follows:

Growth index

(Average twig length) x 100 = Adjusted growth index

100% - Average estimated use prior to

completion of full annual growth

(5) Use index

(a) The use index is an indication of the volume of browse removed. This

index can be used to compare the amounts of browse removed in

different years.

(b) Calculate the use index by multiplying the total percent utilization

times the adjusted growth index and dividing by 100. For example, if

total utilization is 50 percent and the adjusted growth index is 6

inches, the use index is 3. If total utilization is 50 percent and the

adjusted growth index is 3 inches, the use index is 1.5. Although

utilization is the same in both examples, twice as much browse was

removed in the first example.
29

METHODS—BROWSE REMOVAL—Twig Length Measurement

Total percent utilization x Adjusted growth index = Use index

100

h Data Analysis Data analysis consists of calculating confidence intervals around

the average percent utilization estimate.

i References

Jensen, Charles H. and George W. Scotter. 1977. A comparison of twiglength

and browsed-twig methods of determining browse utilization. J. Range

Manage. 30:64-67.

Ferguson, Robert B. and Michael A. Marsden. 1977. Estimating overwinter

bitterbrush utilization from twig diameter-length-weight relations. J. Range

Manage. 30:231-236.

Smith, Arthur D. and Philip J. Urness. 1962. Analyses of the Twig Length

Method of determining utilization of browse. Utah State Dept. of Fish &

Game. Publication No. 62-9. 35p.

U.S. Department of Interior Bureau of Land Management. 1984. Rangeland

Monitoring - Utilization Studies, TR4400-3.
METHODS—BROWSE REMOVAL—Twig Length Measurement

30 Illustration 1 Page of Twig Length Measurement Key Species Allotment Name & Number Pasture Period of Use Study Number Date Examiner Kind and/or Class of Animal 1 2 3 4 5 6 7 8 9 10 11 12 1 2 3 4 5 6 7 8 9 10 11 12 Measurements after full annual growth Nearest 1/2 inch Centimeter Tag No Total Lngth Est Use No Twig Meas Measurements after period of use Total Lngth

Totals Totals

Notes (Use other side or another page, if necessary) (Instructions for calculations on other side)

%

Use

by

Plant
31

METHODS—BROWSE REMOVAL—Twig Length Measurement

Twig Length Measurement Method Form—Calculations:

1. Average estimated use prior to completion of full annual growth

Total estimated % utilization Average estimated use

for the individual plants = prior to completion =

Number of tagged plants of full annual growth

2. Percent utilization by individual plants

Total twig length

by plant after Total twig length

 full annual growth - by plant after period of use x 100 = Percent x 100 =

Total twig length by plant after full utilization

annual growth

3. Total measured percent utilization

Total twig length Total twig length

for all tagged plants - for all plants after

after full annual growth period of use x 100 = Percent x 100 =

Total twig length for all tagged plants utilization

after full annual growth

4. Total percent utilization

Average estimate

used prior to completion of Measured

 full annual growth + percent utilization = Total percent + =

5. Growth index

Total twig length for all tagged

plants after full annual growth

Number of twigs measured = Growth index (Average twig length) =

6. Adjusted growth index

Growth index (Average twig length) x 100 = Adjusted growth x 100 =

100% - Average estimated use prior to index

completion of full annual growth

7. Use index

Total percent utilization x Adjusted growth index = Use index x =

100 100

Illustration 1 page 2


METHODS—BROWSE REMOVAL—Cole Browse

34

2. Cole Browse Method The Cole Browse Method is used to collect utilization

data on browse species. This method provides data on age and form class, availability and hedging, estimated utilization, and growth and use indexes for the

browse component of the plant community. These data are used to make annual

utilization and trend estimates. Separate transects are run for different browse

species.

a Areas of Use This method can be used in a wide variety of vegetation types

where browse key species clearly exhibit annual leader growth.

b Advantages and Limitations The Cole Browse Method is more rapid than

methods that require measurements; however, it is somewhat less accurate

because estimates rather than measurements are used to determine utilization.

There can be considerable variation in utilization estimates as well as in age and

form class estimates among examiners. Plant growth characteristics, weather

conditions, and site conditions may have an equal or greater influence on the

appearance of plants than leader use. In addition, age class and form class may

not always be sensitive indicators of the effects of browsing.

c Equipment

• Study Location and Documentation Data form (see Appendix A)

• Cole Browse form (see Illustration 2)

• Compass

• 10-foot tape

• Steel posts

• Post driver

• 12-inch ruler or metric equivalent

d Training The accuracy of utilization percentage estimates depends on the

thoroughness of training. Examiners should be trained to identify browse species

and to recognize annual leader growth, availability of browse, percent utilization, degree of hedging, and age class of browse plants (see Section III.D.9).

e Establishing Studies Careful establishment of studies is a critical element in

obtaining meaningful data. Select key species and determine the number,

length, and location of the transects (see Section III.B.7).

(1) Collect data using several pilot transects to determine the number of

transects needed and the number of observations to be made on each

transect. These data are needed to determine if a statistically valid sample

has been collected (see Section III.B.7).

(2) At the beginning of each study, determine the transect bearing and distance

between observation points. Select a prominent distant landmark such as a

large tree, rocky point, etc., that can be used as the transect bearing point.

(3) Plot the transects on detailed management unit maps and/or aerial photos

(see beginning of Section III).
35

METHODS—BROWSE REMOVAL—Cole Browse

(4) Permanently mark the location of each study with a reference post and

study location stake (see beginning of Section III).

(5) Number studies for proper identification to ensure that the data collected

can be positively associated with specific studies on the ground

(see Appendix B).

(6) Document the location and other pertinent information concerning the

study on the Study Location and Documentation Data form (see beginning

of Section III and Appendix A).

(7) Temporary transects may be used for locating study sites or for gathering

data on browse stands outside study sites. These transects do not need to

be marked on the ground.

f Sampling Process Collect data beginning with the first selected plant; make

the necessary observations, estimates, and measurements; and then record the

data on the Cole Browse form (see Illustration 2).

(1) Sample only one species on each transect.

(2) Form class Observe the selected plant and check the appropriate Form

Class column on the form.

(a) The form classes are as follows:

No. Form Class

1 All available, little or no hedging

2 All available, moderately hedged

3 All available, severely hedged

4 Partially available, little or no hedging

5 Partially available, moderately hedged

6 Partially available, severely hedged

7 Unavailable

8 Dead

(b) Availability refers to browse available to the animals.

(c) The three degrees of hedging are based on the length and appearance

of two-year-old wood (previous year’s leaders) immediately below the

current leaders (see Appendix D). If more than one degree of hedging

is evident on a plant, form class is based on the predominant or average condition. The three degrees of hedging are:

Little or no hedging - Two-year-old wood is relatively long and unaltered

or only slightly altered.

Moderately hedged - Two-year-old wood is fairly long but most of it has

been altered from the normal growth form.

Severely hedged - Two-year-old wood is relatively short and/or

strongly altered from the normal growth form.
METHODS—BROWSE REMOVAL—Cole Browse

36

(d) Browse plants are considered to reflect the normal growth form when

less than 50 percent of the two-year-old growth (the previous year’s

leaders) has clipped ends and most of the current leaders extend

directly from terminal buds off two-year-old wood. Alterations from

the normal growth form are reflected when 50 percent or more of the

two-year-old wood has clipped ends. Current leaders occur mostly as

extensions from lateral buds off two-year-old wood in the moderately

hedged condition or as clumped lateral and/or adventitious sprouts in

severely hedged condition.

(e) The length of two-year-old wood reflects the relative vigor of the

previous year’s leader growth and/or the effects of prior use. Since the

degrees of hedging are confined to two-year-old wood, they reflect the

effects of use during a previous year, or a succession of previous years.

(f) The three degrees of hedging provide a measure of the relative condition of browse plants and help in assessing the short-term effects of

different intensities of leader use.

(3) Age class Age class data reflect the establishment, survival, and decadence

of key browse plants. Observe the selected plant and check the appropriate Age Class Column on the form. An age class designation is not made

for plants in form classes 7 and 8. The four age classes are:

S - Seedling - New plants that have survived at least one growing season, but are not more than 2 or 3 years old. The basal

stems are generally 1/8 inch or less in diameter.

Y - Young - Young plants usually less than 10 years old. They have an

elongated growth form and simple branching with basal

stems no greater than approximately .5 inch in diameter.

M - Mature - Plants more than 10 years old. They are distinguished by

heavier, often gnarled stems, and complex branching.

Canopy is made up of more than 50 percent living wood.

Basal stems are often greater than .5 inch in diameter.

D - Decadent - Browse plants with more than 50 percent of the canopy

area dead.

(4) Leader use estimates Leader use is an estimate of the intensity of use on

browse plants available to the animals. Estimate the percent of available

leaders that have been browsed on each sample plant. This estimate is

based on the number of leaders that have been browsed and not on the

percent of growth removed. Leader use estimates are not made for plants

in form classes 7 and 8. Determine the use class that the estimate falls in

and enter the class value in the Leader Use Column on the form. For

example, if estimated leader use is 15 percent, then the recorded value will

be 25 percent; if estimated use is 80 percent, the recorded value will be 75

percent. The leader use class percentage ranges and the corresponding

class values are:
37

METHODS—BROWSE REMOVAL—Cole Browse

Leader Use Class Class

Percentage Range Values

0 0

1-10 5

11-40 25

41-60 50

61-90 75

91-100 95

(5) Leader length measurements Measure current growth on each ungrazed

leader on the available portion of each sampled plant on the transect.

These measurements are taken to determine the average annual growth or

growth index. Record these measurements (to the nearest .5 inch or

nearest centimeter) on the back of the form.

(6) Selecting the nearest plant To select the next plant to be sampled, face

toward the transect bearing point, pace the specified distance, and then

select and sample the nearest plant of the key species that occurs within a

180-degree zone (see Appendix C). Repeat this routine until the desired

number of plants have been sampled. To lengthen a transect, increase the

distance between observations (10 paces, 20 paces, etc.). At the end of the

pacing interval, select the nearest plant in the 180-degree zone. Use the

same pacing interval throughout the transect.

g Calculations Make the calculations and record the results in the appropriate

column or blank on the Cole Browse form (see Illustration 2).

(1) Form class summary Total the number of plants in each form class and

enter the value in the Total Column on the form. Calculate the percent

composition by form class as follows:

Total no. of plants in a form class x 100 = Percent composition by form class

Total no. of plants sampled

Enter the value in the Percent Column on the form.

(2) Age class summary Total the number of plants in each age class and enter

the value in the Total Column on the form. Calculate percent composition

by age class as follows:

Total no. of plants in an age class x 100 = Percent composition by age class

Total no. of plants sampled

Enter the value in the Percent Column on the form.
METHODS—BROWSE REMOVAL—Cole Browse

38

(3) Average leader use Calculate the average leader use, being sure to exclude

the number of plants that are dead or unavailable from the total number of

plants sampled:

Total estimated leader use for all plants = Average leader use (%)

Total no. of plants sampled

Record the value on the form.

(4) Average leader length or growth index

(a) The growth index is the average length of the ungrazed leaders on the

sampled plants. This index can be used to compare the amounts of

growth which occur in different years and as an indication of species

vigor.

(b) Calculate the average leader length or growth index as follows:

Total length of ungrazed leaders = Average length of

total no. of leaders measured ungrazed leaders or growth index

Record the value on the form.

(5) Use index

(a) The use index is an indication of the volume of browse removed. This

index can be used to compare amounts of browse removed in different

years.

(b) Calculate the use index by multiplying the average leader use (%)

times the average leader length (growth index) and dividing by 100.

Record the use index on the form. For example, if average leader use

is 50 percent and the average leader length is 6 inches, the use index is

3. If average leader use is 50 percent and the average leader length is 3

inches, the use index is 1.5. Although utilization is the same in both

examples, twice as much browse was removed in the first example.

Average leader use % x Growth index = Use index

100

h Data Analysis Confidence intervals can be constructed around median or

average leader use percentages. The number of individuals in different form and

age classes can be compared to desired or expected values using Chi Square

analysis.

i References

U.S. Department of Interior Bureau of Land Management. 1984. Rangeland

Monitoring - Utilization Studies, TR4400-3.
39

METHODS—BROWSE REMOVAL—Cole Browse

Illustration 2

Cole Browse

Study Number Date Examiner

Allotment Name & Number Pasture

Key Species Kind and/or Class of Animal Period of Use

Pl Form Class

No

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

32

33

34

35

36

37

38

39

40

41

42

43

44

45

46

47

48

49

50

1 2 3 4 5 6 7 8 S Y M D

Age Class Leader

Use -%

Pl Form Class

No 1 3 4 Y

Age Class Leader

2 5 SD 6 7 8 M Use -%

Tot. % Form Classes

1 - All available, Little or no hedging

2 - All available, Moderately hedged

3 - All available, Severely Hedged

4 - Partially available, Little or no hedging

5 - Partially available, Moderately hedged

6 - Partially available, Severely Hedged

Subtotal

7 - Unavailable

8 - Dead

Total

Average Leader Length Use Index

Tot. % Age Classes

S - Seedling, < 1/8" diam.

Y - Young, 1/8" to 1/2" diam.

M - Mature, > 1/2" diam.

D - Decadent, 50% or more dead

Total

Total

Leader Use Class

0%

1-10%

11-40%

41-60%

61-90%

91-100%

Average

Leader

Use

0%

5%

25%

50%

75%

95%

Value

Page of
METHODS—BROWSE REMOVAL—Cole Browse

40 Illustration 2 page 2

Pl Leader Length

No

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

32

33

34

35

36

37

38

39

40

41

42

43

44

45

46

47

48

49

50

Total

Length 1 2 3 4 5 6 7 8 9 10

No

Ldrs.

Meas.

Notes (use another page,

if necessary)

Page 2

Totals

= Total Length

No Leaders Meas.

Average Leader

Length =


43

METHODS—BROWSE REMOVAL—Extensive Browse

3. Extensive Browse Method With the Extensive Browse Method, pace

transects are run to collect vegetation data. This method provides data on utilization, species composition, age class, form classes, availability, and hedging for the

browse component of the plant community.

a Areas of Use This method can be used within a wide variety of vegetation types.

b Advantages and Limitations The Extensive Browse Method is rapid and can

be used on all browse species. It is well adapted to situations where browse

data must be obtained from large areas with limited personnel. All browse

species within the plant community can be sampled on one transect. The

method is more rapid than methods which require measurements. However, it

is somewhat less accurate than measurement methods in determining utilization

because estimates rather than measurements are used. This method is designed

to eliminate personal bias and maximize consistency.

c Equipment

(1) Study Location and Documentation Data form (see Appendix A)

(2) Extensive Browse form (see Illustration 3)

(3) Tally counter (optional)

d Training The accuracy of utilization percentage estimates depends upon the

thoroughness of training. Examiners should be trained to identify browse

species and to recognize annual leader growth, availability of browse, percent

utilization, degree of hedging, and age class of browse plants (see Section III.D.9).

e Establishing Studies Careful establishment of studies is a critical element in

obtaining meaningful data. Select key species and determine the number,

length, and location of the transects (see Section III.B.7).

(1) Collect data using several pilot transects to determine the number of

transects needed and the number of observations to be made on each

transect. These data are needed to determine if a statistically valid sample

has been collected (see Section III.B.7).

(2) At the beginning of each study, determine the transect bearing and distance

between observation points. Select a prominent distant landmark such as a

large tree, rocky point, etc., that can be used as the transect bearing point.

(3) Plot the transects on detailed management unit maps and/or aerial photos

(see beginning of Section III).

(4) Although transects are not permanent, plot them on detailed management

unit maps and/or aerial photos for documentation and future reference.

(5) Number studies for proper identification to ensure that the data collected can

be positively associated with specific studies on the ground (see Appendix B).
METHODS—BROWSE REMOVAL—Extensive Browse

44

(6) Record important information about the transect and any special resource

conditions under “Notes” Extensive Browse form, or on the Study Location

and Documentation Data form (see Illustration 3 and Appendix A )

(7) Locate the “heaviest used” or “representative” areas in a management unit.

The intent is to find several areas used intensively during the period of use.

These may occur in the same general location each year, but will probably

fluctuate. Transects are located in heavy use areas since vegetation changes

which occur as a result of browsing will be evident first on these areas.

f Sampling Process After examiners are trained and are confident in their

ability to recognize the availability of browse, degree of utilization, degree of

hedging, and age classes of browse plants, proceed with the collection of data.

(1) Selecting the sample plants

(a) At the end of each pacing interval, face toward the transect bearing

point and then select and sample the nearest browse plant that occurs

within a 180-degree zone. (See Appendix C for a schematic of the

180-degree selection zone.)

(b) Begin each pacing interval from the last sampled plant. Pace toward

the transect bearing point in the interspaces between browse plants. It

is not necessary to pace in an absolutely straight line.

(2) Collecting data Record utilization estimates as well as the form class and

age class on the selected browse plant by species on the Extensive Browse

form (see Illustration 3). Use a dot count or tally counter to keep track of

the number of plants sampled.

(a) Utilization Select a branch and estimate the amount of utilization of

current annual growth.

- Select a branch at random. For example:

Note the second-hand location or the digital seconds readout on a

watch.

Using the route of travel along the transect line as the 6 o’clock - 12

o’clock line, go to the position on the browse plant that is indicated

by the location of the second hand or the digital second readout.

(Example - 20 seconds represents the 4 o’clock position.)

- Select an available branch on that side of the plant.

Select ten leaders of annual growth and determine the number of

these leaders that show any evidence of use. Convert this number

to percent (i.e., two leaders used equals 20 percent use, six leaders

used equals 60 percent use, etc). Record the value by dot tally in

the appropriate column on the form.
45

METHODS—BROWSE REMOVAL—Extensive Browse

After sampling a total of 50 plants, figure the average utilization for

each species encountered on the first half of the transect. Circle

the plant code for all species averaging 50 percent or greater use

(see Section V.A.3.g).

- Sample points 51-100 as follows:

If the selected plants are one of the circled species, record utilization estimates as well as the form class and age class in the same

manner as for the first 50 plants.

If the next selected plants are not one of the circled species, record

utilization estimates as well as the form class and age class. In

addition, locate the nearest plant of any of the circled species and

record its utilization (only) in the appropriate column opposite the

species plant code. Do not record age class and form class for these

additional plants.

(b) Age class Age class data reflect the establishment, survival, and decadence of key browse plants. Observe the selected plant and record (by

dot tally) the age class by species in the appropriate column on the

form. The four age classes are as follows:

S - Seedling - New plants that have survived at least one growing

season, but are not more than 2 or 3 years old. The

basal stems are generally 1/8 inch or less in diameter.

Y - Young - Young plants usually less than 10 years old. They have an

elongated growth form and simple branching with basal

stems no greater than approximately .5 inch in diameter.

M - Mature - Plants more than 10 years old. They are distinguished by

heavier, often gnarled stems, and complex branching.

Canopy is made up of more than 50 percent living wood.

Basal stems are often greater than .5 inch in diameter.

D - Decadent - Browse plants with more than 50 percent of the

canopy area dead.

(c) Form class Observe the selected plant and record (by dot tally) the

form class by species in the appropriate column on the form.

- The form classes are as follows:

No. Form Class

1 All available, little or no hedging

2 All available, moderately hedged

3 All available, severely hedged

4 Partially available, little or no hedging

5 Partially available, moderately hedged

6 Partially available, severely hedged

7 Unavailable

8 Dead
METHODS—BROWSE REMOVAL—Extensive Browse

46

- Availability refers to browse available to the animals.

- The three degrees of hedging are based on the length and appearance of two-year-old wood (previous year’s leaders) immediately

below the current leaders (see Appendix D). If more than one

degree of hedging is evident on a plant, form class is based on the

predominant or average condition. The three degrees of hedging are:

Little or no hedging - Two-year-old wood is relatively long and

unaltered or only slightly altered.

Moderately hedged - Two-year-old wood is fairly long but most of it

has been altered from the normal growth form.

Severely hedged - Two-year-old wood is relatively short and/or

strongly altered from the normal growth form.

- Browse plants are considered to reflect the normal growth form

when less than 50 percent of the two-year-old growth (the previous

year’s leaders) has clipped ends and a most of the current leaders

extend directly from terminal buds off two-year-old wood. Alterations from the normal growth form are reflected when 50 percent

or more of the two-year-old wood has clipped ends. Current

leaders occur mostly as extensions from lateral buds off two-yearold wood in the moderately hedged condition or as clumped lateral

and/or adventitious sprouts in the severely hedged condition.

- The length of two-year-old wood reflects the relative vigor of the

previous year’s leader growth and/or the effects of prior use. Since

the degrees of hedging are confined to two-year-old wood, they

reflect the effects of use during a previous year, or a succession of

previous years.

- The three degrees of hedging provide a measure of the relative

condition of browse plants and help in assessing the short-term

effects of different intensities of leader use.

g Calculations Make the calculations and record the results in the appropriate

columns on the Extensive Browse form (see Illustration 3).

(1) Average utilization by species

(a) For each species, multiply the number of browse plants tallied in each

percentage block by the percent indicated in the column heading (0,

10, 20, 30, etc.). Add the figures from each block and enter the total

in the Total Percent Utilized Column on the form.

(b) Add the dot tallies for each browse species to determine the total

number of plants sampled of that species and enter the total in the

Number of Plants Column on the form.
47

METHODS—BROWSE REMOVAL—Extensive Browse

(c) Calculate the average percent utilization for each species by dividing

the total percent utilized by the total number of plants. Enter the

value in the Average Percent Utilization Column on the form.

(2) Age class summary Add the dot tallies for each age class and enter the

totals in the Total Number of Plants Row on the form. Because the age

class is determined for 100 plants on the transect, these totals represent the

percent composition by age class for the browse portion of the plant

community.

(3) Form class summary Add the dot tallies for each form class and enter the

totals in the Total Number of Plants Row on the form. Because the form

class is determined for 100 plants on the transect, these totals represent the

percent composition by form class for the browse portion of the plant

community.

(4) Percent composition by species Add the form class dot tallies for each

browse species and enter the total in the Number of Plants Column on the

form. Because the form class is determined for 100 plants on the transect,

these totals represent the species composition percentages for the browse

portion of the plant community.

h Data Analysis Confidence intervals are calculated for average utilization

percentages. The number of individuals in different form and age classes can be

compared to desired or expected values using Chi Square analysis.

i References

Hooper, Jack F. and Harold F. Heady. 1970. An economic analysis of optimum

rates of grazing in the California annual-type grassland. J. Range Manage.

23:307-311.

U.S. Department of Interior Bureau of Land Management. 1984. Rangeland

Monitoring - Utilization Studies, TR4400-3.
METHODS—BROWSE REMOVAL—Extensive Browse

48 Illustration 3

Extensive Browse

Study Number Date Examiner

Allotment Name & Number Pasture

Species

0 10 20 30 40 50 60 70 80 90 100

Kind and/or Class of Animal Period of Use

Percent Utilization Total

%

Utilized

Number

of

Plants

Average

%

Utilized

Species

S YM D 12345678

Age Class Form Class No Plnt

(and %

Comp)

Notes (use other side or another page, if necessary) (Instructions for calculations on other side)

Tot. no. Plants

(and % comp)

Page of
49

METHODS—BROWSE REMOVAL—Extensive Browse

Illustration 3 page 2

Calculating Average Utilization by Species

1. For each species, multiply the number of browse plants tallied in each percentage

block by the percent indicated in the column heading (0, 10, 20, 30, etc.). Add the

figures from each block to determine the total percent utilized.

2. Add the dot tallies for each browse species to determine the total number of plants

sampled of that species.

3. Calculate the average percent utilization for each species by dividing the total

percent utilization by the total number of plants.

Age Class Summary Calculations

Add the dot tallies for each age class. Because the age class is determined for 100 plants

on the transect, these totals represent the percent composition by age class for the

browse portion of the plant community.

From Class Summary Calculations

Add the dot tallies for each form class. Because the form class is determined for 100

plants on the transect, these totals represent the percent composition by form class for

the browse portion of the plant community.

Calculating Composition By Species

Add the form class dot tallies for each browse species. Because the form class is determined for 100 plants on the transect, the totals represent the species composition

percentages for the browse portion of the plant community.

51

METHODS—RESIDUE MEASURING—Stubble Height

B. Residue Measuring Methods

1. Stubble Height Method The concept of this method is to measure stubble

height, or height (in centimeters or inches) of herbage left ungrazed at any given

time. This method, because of its simple application, is becoming a well-accepted

method for expressing rangeland use.

This method would be used after stubble height standards for specific plant communities had been developed. As an example, a stubble height of 4 inches might

be specified to provide streambank protection, to trap sediments, and to rebuild

degraded stream channels in riparian areas.

a Areas of Use Stubble height standards and measurements have been used

primarily in riparian areas; however, this method may also be used for upland

sites. Adequate stubble height on streamside areas is needed at the end of the

growing season for maintenance of plant vigor and streambank protection.

b Advantages and Disadvantages Stubble height measurements are simple,

quick, and accurate. This method can be used to monitor large areas in less time

than is needed with traditional utilization study methods. Statistical reliability

improves because numerous measurements can be taken in a relatively short

time. Limitations of the method may stem from infrequent application in a

variety of rangeland ecosystems. While stubble height has been used with great

success in riparian areas, there needs to be more research in a variety of other

plant communities.

c Equipment

• Study Location and Documentation Data form (see Appendix A)

• Stubble Height form (see Illustration 4)

• Tape measure

d Training Minimal training of examiners is needed to use this method. Examiners must be able to identify the plant species. This method requires measuring

stubble heights of selected key species, which can easily be accomplished by

agency personnel, permittees, or other interested individuals.

e Establishing Studies Careful establishment of studies is a critical element in

obtaining meaningful data. Select key species and determine the number,

length, and location of the transects (see Section III.B.7). Document the location and other pertinent information concerning transects on the Stubble

Height form.

(1) Collect data using several pilot transects to determine the number of

transects needed and the number of observations to be made on each

transect. These data are needed to determine if a statistically valid sample

has been collected (see Section III.B.7).

(2) At the beginning of each study, determine the transect bearing and distance

between observation points. Select a prominent distant landmark such as a

large tree, rocky point, etc., that can be used as the transect bearing point.
METHODS—RESIDUE MEASURING—Stubble Height

52

(3) Plot the transects on detailed management unit maps and/or aerial photos

(see beginning of Section III).

(4) Permanently mark the location of each study with a reference post and

study location stake (see beginning of Section III).

(5) Number studies for proper identification to ensure that the data collected

can be positively associated with specific studies on the ground

(see Appendix B).

(6) Document the location and other pertinent information concerning the

study on the Study Location and Documentation Data form (see beginning

of Section III and Appendix A).

f Sampling Process At specified intervals, measure the stubble height of the key

species nearest to the toe of the right foot and record on the Stubble Height

form (Illustration 4). Measurements should be in inches or centimeters of leaf

stubble left. For riparian sites, sampling should be done along both sides of a

stream segment. For upland sites and wet meadow riparian sites, measurements

should be taken along a predetermined course or transect. In either situation,

stubble height data can be collected using the linear or baseline techniques

described in Section III.A.2.

g Calculations Use data from the Stubble Height form for calculating the

average stubble height by species.

h Data Analysis Confidence levels should be calculated for the median. See

Technical Reference, Measuring & Monitoring Plant Populations, for information on

determining confidence intervals.

i References

Anderson, E. William and Wilbur F. Currier. 1973. Evaluating zones of utilization. J. Range Manage. 26:87-91.

Gierisch, Ralph K. 1967. An adaptation of the grazed plant method for estimating utilization of Thurber fescue. J. Range Manage. 20:108-111.

Lommasson, T. and Chandler Jensen. 1938. Grass volume tables for determining range utilization. Science 87:444.

——— 1943. Determining utilization of range grasses from height-weight

tables. J. Forestry 41:589-593.

McDougald, Neil K. and Richard C. Platt. 1976. A method of determining

utilization for wet mountain meadows on the summit allotment, Sequoia

National Forest, California. J. Range Manage. 29:497-501.

Reid, E.H. and G.D. Pickford. 1941. A comparison of the ocular-estimate byplot and the stubble-height methods for determining percentage utilization

of range grasses. J. Forestry 39:935-941.
53

METHODS—RESIDUE MEASURING—Stubble Height

Illustration 4

Stubble Height

Study Number Date Examiner

Allotment Name & Number Pasture

Site (or)

1234 56

(Record averages on back of form.)

Species

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

32

33

34

35

36

Total

Average

Page of
METHODS—RESIDUE MEASURING—Stubble Height

54 Illustration 4 page 2

Stubble Height Summary

Species Total Stubble Height Number of Plants Average Stubble Height

Totals

Notes:


57

METHODS—RESIDUE MEASURING—Robel Pole

2. Visual Obstruction Method - Robel Pole This method can be used to

determine the amount of standing biomass remaining on an area after a use period.

It is commonly referred to as the Robel Pole Method.

a Areas of Use The Visual Obstruction Method is effective in both upland and

riparian areas where vegetation is less than 4 feet tall.

b Advantages and Disadvantages The Visual Obstruction measurements are

simple, quick, and accurate. This method can be used to monitor height and

vertical density of standing vegetation over large areas quickly.

c Equipment

• Study Location and Documentation Data form (see Appendix A)

• Robel Pole form (see Illustration 5)

• Cover classes for the area or plant community

• Aerial photographs or management unit map

• Robel pole (see Illustration 6)

d Training The accuracy of the data depends on the training and ability of the

examiners. They must receive adequate and consistent training in laying out

transects, determining cover classes, and reading the Robel pole.

e Establishing Studies Careful establishment of studies is a critical element in

obtaining meaningful data. Select key species and determine the number,

length, and location of the transects (see Section III.B.7).

(1) Establish the number of visual cover classes and height limits for each class

based on resource management objectives. These cover classes must be

developed locally for each ecological site or plant community.

The following is an example of cover classes established for upland bird

nesting cover on the Fort Pierre National Grasslands:

Cover Classes Visual Obstruction Height

1 0.0 - 1.9

2 2.0 - 2.9

3 3.0 - 3.9

4 4.0 +

(2) Collect data using several pilot transects to determine the number of

transects needed and the number of observations to be made on each

transect. These data are needed to determine if a statistically valid sample

has been collected (see Section III.B.7).

(3) At the beginning of each study, determine the transect bearing and distance

between observation points. Select a prominent distant landmark such as a

large tree, rocky point, etc., that can be used as the transect bearing point.

(4) Plot the transects on detailed management unit maps and/or aerial photos

(see beginning of Section III).
METHODS—RESIDUE MEASURING—Robel Pole

58

(5) Permanently mark the location of each study with a reference post and

study location stake (see beginning of Section III).

(6) Number studies for proper identification to ensure that the data collected

can be positively associated with specific studies on the ground

(see Appendix B).

(7) Document the location and other pertinent information concerning the

study on the Study Location and Documentation Data form (see beginning

of Section III and Appendix A).

f Sampling Process This technique can be most effectively accomplished

utilizing two individuals.

(1) Start a transect by taking the specified number of paces along the transect

bearing before making the first reading (observation point). Two Visual

Observation (VO) measurements are taken at each observation point from

opposite directions along the contour. One examiner holds the Robel pole

at the observation point, while the second examiner holds the end of the

cord perpendicular to the transect (see Illustration 6). The Visual Observation (VO) measurement is made by determining the highest 1-inch band

totally or partially visible and then assigning the cover class. Record the

cover class on the Robel Pole form (Illustration 5).

(2) Continue the transect by taking readings at the specified intervals along the

transect bearing until the transect is complete. The distance between

observation points can be increased to expand the area sampled.

g Calculations Total the Visual Observation measurements on the Robel Pole

form (Illustration 5) for both readings at each observation points and record at

the bottom of the form. Add these two totals and divide by the total number of

readings.

h Data Analysis Calculate confidence intervals around average heights.

i References

Robel, R.J., J.N. Briggs, A.D.,Dayton, and L.C., Hulbert. 1970. Relationships

Between Visual Obstruction Measurements and Weight of Grassland

Vegetation, J. Range Manage. 23:295.

Robel, R.J. 1970. Possible Role of Behavior in Regulating Greater Prairie

Chickens’ Populations, J. Wildlife Manage. Vol 34 (2).

Snyder, W.D. 1991. Wheat stubble as nesting cover for ring necked pheasants in

northern Colorado. Wildlife Soc. bulletin vol 19(4).

USDA, Forest Service. 1994. Rangeland Analysis and Management Training

Guide, Rocky Mountain Region USDA Forest Service Denver, CO.
59

METHODS—RESIDUE MEASURING—Robel Pole

Illustration 5

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

Total

Grand

Total

Average

Transect #- #- #- #-

Station VO VO VO VO VO VO VO VO

Sampling Interval Study Location

Allotment Name & Number Pasture

Study Number Date Examiner

Robel Pole

Page of

61

METHODS—RESIDUE MEASURING—Robel Pole

Illustration 6

39" 15

13

11

9

7

5

3

1

48"

1 1/8"

157"

Robel Pole

Pole is 1.125 inches in diameter and 48 inches long.

Pole is painted with alternating 1-inch bands of flat white and 

gray colors, starting with white on the bottom. Alternating 1-inch

bands can be extended to the top of the pole if needed.

A single 157-inch (4m) cord is attached to the pole at a height

of 39 inches (1m) to standardize the distance and height at which

readings are taken.

Narrow black numbers corresponding to the number of bands

are painted on the white bands. For example, the bottom white 

band is "1," the next white band is "3," and so on.

A spike is attached to the bottom of the pole so that it can be

pushed into the ground, allowing one examiner to make the

readings. The spike can be removed if not needed. 

1.

2.

3.

4.

5.
METHODS—RESIDUE MEASURING—Comparative Yield

62

3. Comparative Yield Method This method is used to estimate standing crop or

production of a site remaining after a use period. The total production in a sample

quadrat is compared to one of five reference quadrats; relative ranks are recorded

rather than estimating the weight directly.

a Areas of Use This method works best for herbaceous vegetation but can also

be used successfully with small shrubs and half-shrubs. As with most production estimates, the Comparative Yield method can be used to compare relative

production between different sites.

b Advantages and Limitations The advantage of the comparative yield method

is that a large number of samples can be obtained quickly. Total production is

evaluated, so clipping calibration on a species basis is not needed. The process

of developing reference quadrats for ranking purposes reduces both sampling

and training time. Identification of individual species is not required.

Large-shrub vegetation communities are not well suited for this technique.

c Equipment

• Study Location and Documentation Data form (see Appendix A)

• Comparative Yield form (see Illustration 7)

• Five sampling quadrat frames (see Illustration 8)

• Clippers

• Paper bags

• Kilogram and gram spring-loaded scale with clip

• Compass

d Training Examiners must calibrate their estimates when sampling situations

change (i.e., different sites, time of day, change of season).

e Establishing Studies Careful establishment of studies is a critical element in

obtaining meaningful data. Select key species and determine the number,

length, and location of the transects (see Section III.B.7). Depending on management objectives, comparative yield data can be collected on either permanent or

temporary transects.

(1) Collect data using several pilot transects to determine the number of

transects needed and the number of observations to be made on each

transect. These data are needed to determine if a statistically valid sample

has been collected (see Section III.B.7).

(2) The criteria for selecting the proper size quadrat are the same as for any

weight estimate procedure (see the Interagency Technical Reference,

Sampling Vegetation Attributes). Use the same size quadrat throughout a

study.

(3) Establish one transect on each study site; establish more if needed. More

than one transect may be required for each study site.
63

METHODS—RESIDUE MEASURING—Comparative Yield

(4) At the study location, determine the transect bearing and select a prominent distant landmark such as a peak, rocky point, etc., that can be used as

the transect bearing point.

(5) Number studies for proper identification to ensure that the data collected

can be positively associated with specific studies on the ground

(see Appendix B).

(6) Document the location and other pertinent information concerning the

study on the Study Location and Documentation Data form (see beginning

of Section III and Appendix A).

(7) Plot the transects on detailed management unit maps and/or aerial photos

(see beginning of Section III).

(8) Permanently mark the location of each study with a reference post and

study location stake (see beginning of Section III).

f Sampling Process

(1) A set of reference quadrats must be established. The sample quadrats will

be compared and rated back to these reference quadrats. The reference

quadrats represent the range in dry weight of standing crop that will be

commonly found during sampling.

(a) Five reference quadrats are subjectively located. References 1 and 5

are located first. The first quadrat (reference 1) is placed in a lowyielding or the heaviest grazed area which represents the low-yielding

situations commonly encountered on the site (avoid bare or nearly

bare quadrats). Reference 5 is determined by placing a quadrat on a

high-yielding area; exclude unusually dense patches of vegetation that

would have a rare chance of being sampled. The examiner should

make a mental note of the amount of production and level of utilization in each of the reference quadrats. These references are then

clipped and weighed. If the clipped weight in reference 5 is more

than five times the weight found in reference 1, then two new sites

should be selected as references 1 and 5. In establishing the initial

reference quadrats, the weight in reference 5 is usually too high and

the weight in reference 1 is too low. Make sure reference 5 does not

represent a rare situation. When references 1 and 5 have been selected, reference 3 is located by placing a frame in an area considered

to have a yield halfway between references 1 and 5. References 2 and

4 are located the same way by selecting the mid-point yield between

references 1 and 3 and references 3 and 5, respectively.

(b) All five quadrats are clipped and weighed to compare the reference

quadrats to a linear distribution of quadrat weights. This process is

repeated by clipping additional quadrats until the weights of the five

reference quadrats are approximately linear and observers are confident in their ability to rank quadrats relative to one of the five

references. If the rankings are not linear, the precision of the method
METHODS—RESIDUE MEASURING—Comparative Yield

64

will be reduced. If more than five percent of the quadrats have no

production, then a larger quadrat frame should be used.

(c) In areas with less than 500 lb/ac, small quadrats are difficult to evaluate. In these situations, either larger quadrats should be used or three

reference quadrats should be established instead of five.

(2) Collecting the Data

(a) Start a transect by randomly selecting a point in the study site, taking

five paces along the transect bearing, and then ranking the first quadrat.

(b) Read additional quadrats at specified intervals. To change the length

of the transect, increase the number of paces between quadrats.

(c) For each quadrat, compare the total yield in the quadrat to the references and record the appropriate rank by dot count tally. It is appropriate to assign intermediate ranks if the yield is at the midpoint

between two references. For example, if a quadrat has a yield between

references 1 and 2, assign a rank of 1.5. If a quadrat yield greatly

exceeds the yield of reference 5, then a higher rank may be estimated.

For example, if a quadrat is 50% greater than reference 5, a rank of 7

could be recorded. If more than five percent of the quadrats are

ranked above 5, the references were not properly selected.

(d) To calibrate the ranks, several quadrats representing each reference

should be clipped and weighed independently of the transect line.

The total yield in each quadrat is determined without regard to species. Be sure to save all clipped material. The reference quadrats can

be used as part of these clipped quadrats. The more quadrats clipped,

the better the calibration. Each distinct sampling period should have a

separate calibration. Bags can be weighed in the field to determine

green weight and then saved and dried to determine dry weight.

These weights are then used to determine average weight per reference.

(e) It is recommended that 100 to 200 quadrats be ranked for each site.

g Calculations The number of quadrats tallied for each ranking is totaled

(Illustration 7, column 2) and multiplied by the ranking (column 1).

Rank x Tally = Weighted ranking

These weighted rankings (column 3) are summed and divided by the number of

total quadrats. This indicates the average ranking for the site.

Total rank = Average ranking for the site

Total number of quadrats sampled

The average yield may be estimated with a ratio estimate (described below) or a

least-squares regression technique. The ratio estimate is good for quick field

calculations, but the least-squares regression should be used for final data analysis.
65

METHODS—RESIDUE MEASURING—Comparative Yield

To use the ratio estimate technique, calculate the average rank and average

clipped weight of the harvested quadrats by dividing the total of the clipped

rankings and the total clipped weight by the number of harvested (clipped)

quadrats (column 4 and 5).

Total of clipped rankings = Average rank of clipped quadrats

Total number of clipped quadrats

Total clipped weight = Average weight of clipped quadrats

Total number of clipped quadrats

The average clipped weight is then divided by the average rank to determine

the average rank interval.

Average weight of clipped quadrats = Average rank interval (ARI)

Average rank of clipped quadrats

The average ranking for the site—which is based on the estimated, not clipped,

quadrats—is then multiplied by the average rank interval to estimate the average yield per quadrat for the site.

Average ranking for the site x Average rank interval = Average yield/Quadrat.

The average yield in grams per quadrat obtained above can be converted to

either pounds/acre or kilograms/hectare.

Use the following table to convert grams to pounds per acre if the total area

sampled is a multiple of 9.6 ft2

.

Table 1

(# of quadrats x size = total area )

(10 x 0.96 = 9.6 ft2) multiply grams times 10.0 = pounds per acre

(10 x 1.92 = 19.2 ft2) multiply grams times 5.0 = pounds per acre

(10 x 2.4 = 24.0 ft2) multiply grams times 4.0 = pounds per acre

(10 x 4.8 = 48.0 ft2) multiply grams times 2.0 = pounds per acre

(10 x 9.6 = 96.0 ft2) multiply grams times 1.0 = pounds per acre

(10 x 96.0 = 960.0 ft2) multiply grams times 0.1 = pounds per acre

To convert to kilograms per hectare, first determine the number of quadrats in a

hectare by dividing the number of square meters in a hectare (10,000 m2

) by

the total area (in square meters) of the quadrat. Then divide the number of

quadrats in a hectare by 1,000 to arrive at the conversion factor used to convert

grams per quadrat into kilograms per hectare.

For example, if the quadrat size is 40 x 40 centimeters (0.4 x 0.4 meters), then

the quadrat area would be 0.4 multiplied by 0.4, or .16 m2

. The number of

quadrats in a hectare is calculated by dividing 10,000 by .16, which works out

to 62,500 quadrats per acre. Dividing this number by 1,000 results in the

conversion factor, which is 62.5. The final step is to multiply the average yield

per quadrat obtained from the final equation above by 62.5 to arrive at

kilograms per hectare.

Revised 2/97
METHODS—RESIDUE MEASURING—Comparative Yield

66

h Data Analysis Calculate confidence intervals around the estimate of average

pounds per acre or kilograms per hectare.

i References

Despain, D.W., P.R. Ogden, and E.L. Smith. 1991. Plant frequency sampling for

monitoring rangelands. In: G.B. Ruyle, ed. Some Methods for Monitoring

Rangelands and other Natural Area Vegetation. Extension Report 9043,

University of Arizona, College of Agriculture, Tucson, AZ.
67

METHODS—RESIDUE MEASURING—Comparative Yield

Study Location

Notes

Sampled Quadrats Harvested Quadrat

Rank (1) Tally (2) Rank x Tally (3) Clip Rank (4) Clip Weight (5)

0

.5

1

1.5

2

2.5

3

3.5

4

4.5

5

Total

Average

Page of

Comparative Yield

Allotment Name & Number Number of Quadrats Quadrat Size

Study Number Date Examiner Pasture

Illustration 7

69

METHODS—RESIDUE MEASURING—Comparative Yield

The frame is made of 3/8-inch

iron rod and 1-inch angle iron

or 1 1/4-inch x 3/16-inch flat iron.

Comparative Yield Quadrat Frame

40 cm

40 cm

Quadrat size should be based on local conditions

determined from the pilot study.

1 7.5 x 7.5 cm 56.25 sq cm

2 15.0 x 15.0 cm 225.00 sq cm

3 30.0 x 30.0 cm 900.00 sq cm

4 40.0 x 40.0 cm 1600.00 sq cm

5 50.0 x 50.0 cm 2500.00 sq cm

6 20.0 x 50.0 cm 1000.00 sq cm

Number Size

QUADRAT

Area

Illustration 8
METHODS—HERBACEOUS REMOVAL—Paired Plot

70

C. Herbaceous Removal Methods

1. Paired Plot Method Under the Paired Plot Method, forage from protected and

unprotected plots is clipped and weighed at the end of the use period. The difference between these two weights represents the amount of forage consumed or

otherwise destroyed during that period.

a Areas of Use This method is suitable for all vegetation growth forms for

which production and utilization data are commonly desired. It is particularly

applicable where periods of use are short, use is relatively uniform, and regrowth after foraging is not significant.

b Advantages and Disadvantages

(1) This method is a simple and direct way of measuring utilization.

(2) Little training is required and accuracy is generally high.

(3) This method is time consuming, and ungrazed areas that are protected

from foraging are required.

(4) Where periods of use are long, this method does not provide information

about the cumulative production of foraged plants unless the cages are

moved at short time intervals.

(5) New plots must always be established once the study plots have been

clipped.

c Equipment

• Study Location and Documentation Data form (see Appendix A)

• Paired Plot form (see Illustration 9)

• Frames to delineate plots

• Portable cages to protect plots (see Appendix E)

• Stakes for anchoring cages

• Hammer

• Clipping shears

• Paper sacks

• Spring scale, calibrated in grams

d Training The Paired Plot Method does not require intensive field training,

although examiners must be able to identify plant species. Examiners can

perform the clipping and weighing procedures after only a short training period.

e Establishing Studies Careful establishment of studies is a critical element in

obtaining meaningful data. Select key species and determine the number,

length, and location of the transects (see Section III.B.7).

(1) Collect data using several pilot transects to determine the number of

transects needed and the number of observations to be made on each
71

METHODS—HERBACEOUS REMOVAL—Paired Plot

transect. These data are needed to determine if a statistically valid sample

has been collected (see Section III.B.7).

(2) Site selection and layout.

(a) Select plots to be examined at random (see Section III.B.2).

(b) The number of plots selected depends on the purpose for which the

estimates are to be used, uniformity of the vegetation, and other

factors. (See Section III.B.7 for statistical considerations.)

(c) Adapt the size and shape of plots to the vegetation community to be

sampled.

(3) Anchor a cage over one of the paired plots at each plot location. See

Appendix E for examples of several kinds of utilization cages. The base of

a cage should be large enough to provide at least a 6-inch buffer zone

between the edge of the plot and the side of the cage. The lower portion

of the cage (to approximately 1 to 2 feet high) may be covered with net

wire small enough to exclude rabbits and rodents. Generally, the larger the

mesh, the less influence the cage has in modifying the environment.

(4) Protected plots may be located in exclosures. These plots need not be

caged unless it is necessary to exclude rabbits and rodents.

(a) If protected plots are located within permanent exclosures, caution

must be exercised to ensure that these plots are representative of the

unforaged situation outside the exclosures. Plant composition and

growth must be similar. The area inside a permanent exclosure may

have a different environment due to nonuse.

(b) Protected plots may be located within temporary exclosures, such as

exclosures constructed with electric fence. Plots protected by temporary exclosures can be moved every year to eliminate the artificial

environment created by continued non-use in permanent exclosures.

(5) Leave one plot of each pair open to foraging. If past experience shows that

foraging is particularly uneven, leave two or more plots open for each one

caged in order to average the unevenly foraged conditions. Animals are

attracted to cages and may trample unprotected plots if located too near

protected plots. Therefore, establish unprotected plots a minimum of 100

feet from protected plots. Unprotected plots should be inconspicuously

marked to avoid attracting animals.

(6) Plot the transects on detailed management unit maps and/or aerial photos

(see beginning of Section III).

(7) Permanently mark the location of each study with a reference post and

study location stake (see beginning of Section III).
METHODS—HERBACEOUS REMOVAL—Paired Plot

72

(8) Number studies for proper identification to ensure that the data collected

can be positively associated with specific studies on the ground

(see Appendix B).

(9) Document the location and other pertinent information concerning the

study on the Study Location and Documentation Data form (see beginning

of Section III and Appendix A).

f Sampling Process After examiners are trained, proceed with the collection of

utilization data.

(1) Clip the current year’s growth on key species from protected and

unprotected plots.

(2) On herbaceous species, clip all current year’s growth to within 1 inch of

the ground to save the root crown.

(3) On browse species, remove all current year’s growth available for foraging

animals. For large browse plants, the available current year’s growth may

be removed from part of the plant rather then from the whole plant. The

portion of the browse removed is then converted to total weight based on

sample size. (Example: If one-fourth of the available current year’s

growth of browse plants is removed, the weight of the browse removed

times four equals the total weight.)

(4) Put the clippings from the protected and unprotected plots in separate

paper sacks for weighing.

(5) Weigh the sacks of clipped plants and record separately the weight from

the protected and unprotected plots on the Paired Plot form (see Illustration 9).

Subtract the weight of the sack before recording the weights of the plants.

g Calculations

(1) Calculate the percent utilization as follows:

% utilization = Total protected weight - Total unprotected weight x 100

Total protected weight

(2) If an unequal number of protected and unprotected plots are used in the

study, calculate the percent utilization as follows:

Average weight Average weight

% utilization = for protected plots - for unprotected plots x 100

Average weight for protected plots

(3) Record the percent utilization on the Paired Plot form (see Illustration 9).
73

METHODS—HERBACEOUS REMOVAL—Paired Plot

h Data Analysis Calculate confidence intervals around the estimate of average

percent utilization.

i References

Frischknecht, Neil C. and Paul W. Conrad. 1965. Adaptable, transportable

utilization cages. J. Range Manage. 18:33-34.

U.S. Department of Interior Bureau of Land Management. 1984. Rangeland

Monitoring - Utilization Studies, TR4400-3.
METHODS—HERBACEOUS REMOVAL—Paired Plot

74

Paired Plot

Study Number Date Examiner

Allotment Name & Number Pasture

Page of

Kind and/or Class of Animal Period of Use

Weight in grams by plot

1 2345

Plot

1

Key Species

Location of Paired Plot 1 Location of Paired Plot 2

2

4

3

Total Average Utilization (sum of

percent utilization per pair divided

by total number pairs

P*

U**

P - U

P-U

P x 100

P*

U**

P - U

P-U

P x 100

P*

U**

P - U

P-U

P x 100

P*

U**

P - U

P-U

P x 100

* Protected Plots ** Unprotected Plots

Notes (Use other side or another page if necessary)

Location of Paired Plot 3 Location of Paired Plot 4

Location of Paired Plot 5

Illustration 9

METHODS—HERBACEOUS REMOVAL—Ocular Estimate

76

2. Ocular Estimate With the Ocular Estimate Method, utilization is determined

along a transect by ocular estimate. The percentage by weight of forage removed is

determined for individual plants of the key species or from all plants of the key

species within small quadrats.

a Areas of Use This method has wide applicability and is suited for use with

both grasses and forbs.

b Advantages and Limitations

(1) The most important advantage is speed.

(2) The method is reasonably accurate, depending upon the ability of the

examiners.

(3) Vegetation is not disturbed.

(4) Reliability of estimates is increased by limiting observations to individual

plants or small areas (quadrats).

(5) Errors in personal judgement on individual plants or quadrats frequently

tend to be compensating.

(6) A limitation is that exclosures, cages, or fenced areas may be needed for

training.

c Equipment

• Study Location and Documentation Data form (see Appendix A)

• Ocular Estimate form (see Illustration 10)

• Frames to delineate quadrats (if necessary)

• Clipping shears

• Paper sacks

• Spring scale, calibrated in grams

• Cages as required (see Appendix E)

d Training The accuracy of estimating utilization percentages is depends upon

thoroughness of training and the ability of examiners to identify plant species

and the amount of use. The examiners must first compare ocular estimates

against actual weight values obtained by clipping and weighing (see Section III.D.9).

(1) Locating training sites Locate sites for training purposes on similar

unforaged or protected sites. If it is unlikely that a site containing

unforaged vegetation will be available after the foraging season, it will be

necessary to construct temporary exclosures or install cages on study sites

prior to the period of use.

(2) Making ocular estimates Training involves estimating utilization on

individual plants of the key species or on all plants of the key species

within a small quadrat. If quadrats are to be used for the studies, use

quadrats of the same size for training. The quadrats should be small
77

METHODS—HERBACEOUS REMOVAL—Ocular Estimate

enough so that the entire quadrat is clearly visible to the examiner.

Examiners should practice making ocular estimates as follows:

(a) Clip individual plants of the key species, or plants of key species on a

quadrat, to simulate foraging (sample A).

(b) Estimate the percentage of weight removed.

(c) Clip the remaining forage of the selected plants by removing all

current year’s growth available to the foraging animals (sample B).

(d) Put the clippings for samples A and B in separate sacks

(e) Weigh samples A and B separately and subtract sack weight from the

weight of each sample.

(f) Calculate the percent simulated use by dividing the weight of sample

A by the combined weight of samples A and B and multiplying the

value by 100.

(g) Compare estimates with actual percent forage removed and determine

the error of the estimates. Continue training until examiners can

recognize the different percentages of use.

(3) Checking ocular estimates Training checks should be made and recorded

each day prior to field estimation. This gives a permanent record of the

accuracy of each examiner’s ocular estimates.

e Establishing Studies Careful establishment of studies is a critical element in

obtaining meaningful data. Select key species and determine the number,

length, and location of the transects (see Section III.B.7).

(1) Collect data using several pilot transects to determine the number of

transects needed and the number of observations to be made on each

transect. These data are needed to determine if a statistically valid sample

has been collected (see Section III.B.7).

(2) At the beginning of each study, determine the transect bearing and distance

between observation points. Select a prominent distant landmark such as a

large tree, rocky point, etc., that can be used as the transect bearing point.

(3) Plot the transects on detailed management unit maps and/or aerial photos

(see beginning of Section III).

(4) Permanently mark the location of each study with a reference post and

study location stake (see beginning of Section III).

(5) Number studies for proper identification to ensure that the data collected

can be positively associated with specific studies on the ground

(see Appendix B).
METHODS—HERBACEOUS REMOVAL—Ocular Estimate

78

(6) Document the location and other pertinent information concerning the

study on the Study Location and Documentation Data form (see beginning

of Section III and Appendix A).

f Sampling Process After examiners are trained and are confident in their

ability to recognize degrees of utilization, proceed with the collection of

utilization data.

(1) At each interval along a transect, select the plant of the key species nearest

the toe and estimate and record the percent utilization.

(2) If a quadrat is used, place the frame immediately in front of the toe and

then estimate and record the percent utilization. If the key species does

not occur in the quadrat, proceed along the transect until the key species is

encountered. A quadrat is particularly important for mat- or sod-forming

grasses or forbs.

(3) Record the percent utilization on the Ocular Estimate form (see

Illustration 10).

g Calculations Calculate the average percent utilization by totaling the utilization estimates for the plants or quadrats along the transect and dividing the total

by the number of sampled plants or quadrats. Record the average utilization on

the Ocular Estimate form (see Illustration 10).

h Data Analysis Calculate confidence intervals around the estimate of average

percent utilization.

i References

Reid, E.H. and G.D. Pickford. 1941. A comparison of the ocular-estimate byplot and the stubble-height methods for determining percentage utilization

of range grasses. J. Forestry 39:935-941.

U.S. Department of Interior Bureau of Land Management. 1984. Rangeland

Monitoring - Utilization Studies, TR4400-3.
79

METHODS—HERBACEOUS REMOVAL—Ocular Estimate

Study Number Date Examiner

Allotment Name & Number Pasture

Page of

Kind and/or Class of Animal Period of Use

Key

Species 1 2345

Ocular estimates by plant (or plot)

6 7 8 9 10 12 13 14 15 11 Total

Total ÷ no. of samples (plants or plots) = avg. percent utilization ÷ =

Notes (Use other side or another page, if necessary)

Key

Species 1 2345

Ocular estimates by plant (or plot)

6 7 8 9 10 12 13 14 15 11 Total

Total ÷ no. of samples (plants or plots) = avg. percent utilization ÷ =

Notes (Use other side or another page, if necessary)

Ocular Estimate

Illustration 10

81

METHODS—HERBACEOUS REMOVAL—Key Species

3. Key Species Method (formerly the Modified Key Forage Plant

Method) This technique is a combination of the Landscape Appearance Method

(Section V.D) and the Ocular Estimate Method (Section V.C.2). Utilization levels

are based on an ocular estimate of the amount of forage removed by weight on individual key species and observations are recorded in one of seven utilization classes.

a Areas of Use This method is adapted to areas where perennial grasses, forbs,

and/or browse plants are the key species.

b Advantages and Limitations This method is rapid. The estimated percentage

of forage removed is recorded in one of seven broad classes rather than as a

precise amount. The method is also reasonably accurate, depending upon the

ability of the examiners. Different examiners are more likely to estimate utilization in the same classes than to estimate the same utilization percentages.

Vegetation is not disturbed. Reliability of estimates is increased by limiting

observations to individual plants or small areas (quadrats). A limitation is that

exclosures, cages, or fenced areas may be needed for training.

c Equipment

• Study Location and Documentation Data form (see Appendix A)

• Key Species form (see Illustration 11)

• Tally counter (optional)

• Frames to delineate quadrats (if necessary)

• Clipping shears

• Paper sacks

• Spring scale, calibrated in grams

• Cages as required (see Appendix E)

d Training The accuracy of estimating utilization percentages depends upon

thoroughness of training and the ability of examiners to identify plant species

and the amount of use. The examiners must first compare their ocular estimates against actual weight values obtained by clipping and weighing

(see Section III.D.9).

(1) Locating training sites Locate sites for training purposes on similar

unforaged or protected sites. If it is unlikely that a site containing

unforaged vegetation will be available after the foraging season, it will be

necessary to construct temporary exclosures or install cages on study sites

prior to the period of use.

(2) Making ocular estimates Training involves estimating utilization on

individual plants of the key species or on all plants of the key species on a

small quadrat. If quadrats are to be used for the studies, use quadrats of

the same size for training. The quadrats should be small enough so that the

entire quadrat is clearly visible to the examiner. Examiners should practice

making ocular estimates as follows:

(a) Clip individual plants of the key species, or plants of the key species

on a quadrat, to simulate foraging (sample A).
METHODS—HERBACEOUS REMOVAL—Key Species

82

(b) Estimate the percentage of weight removed.

(c) Clip the remaining forage of the selected plants by removing all

current year’s growth available to the foraging animals (sample B).

(d) Put the clippings for samples A and B in separate paper sacks.

(e) Weigh samples A and B separately and subtract sack weight from the

weight of each sample.

(f) Calculate the percent simulated use by dividing the weight of sample

A by the combined weight of samples A and B and multiplying the

value by 100.

(g) Compare estimates with the actual percent forage removed and

determine the error of the estimates. Continue training until examiners

can recognize the different percentages of use.

(3) Identifying utilization classes Examiners must be able to recognize the

seven herbaceous or seven browse utilization classes using the written class

descriptions.

e Establishing Studies Careful establishment of studies is a critical element in

obtaining meaningful data. Select key species and determine the number,

length, and location of the transects (see Section III.B.7).

(1) Collect data using several pilot transects to determine the number of

transects needed and the number of observations to be made on each

transect. These data are needed to determine if a statistically valid sample

has been collected (see Section III.B.7).

(2) At the beginning of each study, determine the transect bearing and distance

between observation points. Select a prominent distant landmark such as a

large tree, rocky point, etc., that can be used as the transect bearing point.

(3) Plot the transects on detailed management unit maps and/or aerial photos

(see beginning of Section III).

(4) Permanently mark the location of each study with a reference post and

study location stake (see beginning of Section III).

(5) Number studies for proper identification to ensure that the data collected

can be positively associated with specific studies on the ground

(see Appendix B).

(6) Document the location and other pertinent information concerning the

study on the Study Location and Documentation Data form (see beginning

of Section III and Appendix A).

f Sampling Process After examiners are trained and are confident in their

ability to recognize various degrees of utilization, proceed with the collection of

utilization data.
83

METHODS—HERBACEOUS REMOVAL—Key Species

(1) Sampling techniques

(a) At each interval along a transect, select the plant of the key species

nearest the toe and estimate and record the percent utilization by weight.

(b) If a quadrat is being used, place the frame immediately in front of the

toe and estimate and record the percent utilization. If the key species

does not occur in the quadrat, proceed along the transect until the key

species is encountered.

(c) Record each observation by dot count in the appropriate utilization

class on the Key Species form (see Illustration 11).

(2) Herbaceous utilization classes Seven utilization classes are used to show

relative degrees of use of key herbaceous species (grasses and forbs). Each

class represents a numerical range of percent utilization. Utilization

estimates must be placed in one of the seven classes. Utilization classes are

as follows:

(a) (0-5%). The key species show no evidence of grazing use or negligible

use.

(b) (6-20%). The key species has the appearance of very light grazing.

Plants may be topped or slightly used. Current seedstalks and young

plants are little disturbed.

(c) (21-40%). The key species may be topped, skimmed, or grazed in

patches. Between 60 and 80 percent of current seedstalks remain

intact. Most young plants are undamaged.

(d) (41-60%). Half of the available forage (by weight)on key species

appears to have been utilized. Fifteen to 25 percent of current

seedstalks remain intact.

(e) (61-80%). More than half of the available forage on key species

appears to have been utilized. Less than 10 percent of the current

seedstalks remain. Shoots of rhizomatous grasses are missing.

(f) (81-94). The key species appears to have been heavily utilized and

there are indications of repeated use. There is no evidence of

reproduction or current seedstalks.

(g) (95-100). The key species appears to have been completely utilized.

The remaining stubble is utilized to the soil surface.

(3) Browse Utilization Classes Seven utilization classes show relative degrees

of use of available current year’s growth (leaders) of key browse plants

(shrubs, half shrubs, woody vines, and trees). Each class represents a

numerical range of percent utilization. Estimate utilization within one of

the seven classes. Utilization classes are as follows:
METHODS—HERBACEOUS REMOVAL—Key Species

84

(a) (0-5%). The key browse plants show no evidence of grazing use or

only negligible use.

(b) (6-20%). The key browse plants have the appearance of very light use.

The available leaders are little disturbed.

(c) (21-40%). There is obvious evidence of leader use. The available

leaders appear cropped or browsed in patches and 60 to 80% of the

available leader growth remains intact.

(d) (41-60%). Key browse plants appear rather uniformly utilized and 40

to 60% of the available leader growth remains intact.

(e) (61-80%). The key browse plants are hedged and some plant clumps

may be slightly broken. Nearly all available leaders are used and few

terminal buds remain. Between 20 and 40% of the available leader

growth remains intact.

(f) (81-94%). There are indications the key browse species have been

utilized repeatedly. There is no evidence of terminal buds and usually

less than 20% of available leader growth remains intact. Some, and

often much, of the second and third years’ growth has been utilized.

Hedging is readily apparent. Key browse plants frequently have

broken branches.

(g) (95-100). Less than 5% of the available leader growth on the key

browse plants remain intact. Most of the second and third years’ growth

have been utilized. All key browse plants have major portions broken.

g Calculations Calculate the percent utilization as follows:

(1) Convert the dot count to the number of observations for each utilization class.

(2) Multiply the number of observations in each utilization class times the

midpoints of the class intervals.

(3) Total the products for all classes.

(4) Divide the sum by the total number of observations on the transect.

(5) Record the average percent utilization on the Key Species form

(see Illustration 11).

h Data Analysis Calculate confidence intervals around the estimate of average

percent utilization.
85

METHODS—HERBACEOUS REMOVAL—Key Species

i References

Anderson, E. William and Wilbur F. Currier. 1973. Evaluating zones of utilization.

J. Range Manage. 26:87-91.

Heady, Harold F. 1949. Methods of determining utilization of range forage. J.

Range Manage. 2:53-63.

U.S. Department of Interior Bureau of Land Management. 1984. Rangeland

Monitoring - Utilization Studies, TR4400-3.
METHODS—HERBACEOUS REMOVAL—Key Species

86 Illustration 11

No. X

Midpt.

(C)(M)

No. By

Class

(C)

Dot

Count

No. X

Midmt.

(C)(M)

No. By

Class

(C)

Dot

Count

Int

Mid

(M)

2.5

88

70

50

13

30

0-5%

6-20%

Class

Interval

61-80%

81-94%

21-40%

41-60%

Study Number Date Examiner

Allotment Name & Number Pasture

Kind and/or Class of Animal Period of Use

Notes (use other side or another page, if necessary)

= = = ∑(CM)*

∑C

Avg.

Util.

Totals Totals

95-100% 97.5

(a) (0-5%). The key species show no evidence of

grazing use or negligible use.

(b) (6-20%). The key species has the appearance of

very light grazing. Plants may be topped or slightly

used. Current seedstalks and young plants are little

disturbed.

(c) (21-40%). The key species may be topped,

skimmed, or grazed in patches. Between 60 and 80

percent of current seedstalks remain intact. Most

young plants are undamaged.

(d) (41-60%). Half of the available forage (by weight)

on key species appears to have been utilized. Fifteen

to 25 percent of current seedstalks remain intact.

(e) (61-80%). More than half of the available forage

on key species appears to have been utilized. Less

than 10 percent of the current seedstalks remain.

Shoots of rhizomatous grasses are missing.

(f) (81-94%). The key species appear to have been

heavily utilized and there are indications of repeated

use. There is no evidence of reproduction or current

seedstalks.

(g) (95-100%). The key species appears to have been

completely utilized. The remaining stubble is utilized

to the soil surface.

Key Species Key Species

Key Species

Page of

* Where C = The number of observations within each class interval (C column),

M = the class interval midpoint (M column), and ∑ = the summation symbol.
87

METHODS—HERBACEOUS REMOVAL—Key Species

Browse Utilization Classes

1. (0-5%). The key browse plants show no evidence of grazing use or only negligible use.

2. (6-20%). The key browse plants have the appearance of very light use. The available leaders are little disturbed.

3. (21-40%). There is obvious evidence of leader use. The available leaders appear

cropped or browsed in patches and 60 to 80% of the available leader growth remains

intact.

4. (41-60%). Key browse plants appear rather uniformly utilized and 40 to 60% of the

available leader growth remains intact.

5. (61-80%). The key browse plants are hedged and some plant clumps may be slightly

broken. Nearly all available leaders are used and few terminal buds remain. Between

20 and 40% of the available leader growth remains intact.

6. (81-94%). There are indications the key browse species have been utilized repeatedly. There is no evidence of terminal buds and usually less than 20% of available

leader growth remains intact. Some, and often much, of the second and third years’

growth has been utilized. Hedging is readily apparent. Key browse plants frequently

have broken branches.

7. (95-100). Less than 5% of the available leader growth on the key browse plants

remains intact. Most of the second and third years’ growth has been utilized. All

key browse plants have major portions broken.

Illustration 11 page 2

89

METHODS—HERBACEOUS REMOVAL—Height-Weight

4. Height-Weight Method The Height-Weight Method involves the measurement of heights of ungrazed and grazed grass or grasslike plants to determine

average utilization. Measurements of plant heights recorded along transects are

converted to percent of weight utilized by means of a utilization gauge

(Lommasson and Jensen 1943). The utilization gauge is developed from heightweight relationship curves. This method provides a mechanical tool which can be

used for training, checking personal judgment, and promoting uniformity of results

between examiners, as well as for determining percent utilization.

a Areas of Use This method is adapted for obtaining utilization data where the key

species are either bunch or rhizomatous/sod-forming grasses or grasslike species.

b Advantages and Limitations This method provides uniform, accurate, and

reliable utilization determinations for perennial grasses and grasslike species. It

is an objective method; however, some estimation is required. This method

requires numerous ungrazed plants, which may be hard to locate. Accurate

utilization scales may not be available for the key species. The development of

the height-weight relationship curves and preparation of utilization gauges

scales can be time-consuming. This method cannot be used for determining

utilization of forbs and shrubs.

c Equipment

• Study Location and Documentation Data form (see Appendix A)

• Height-Weight form (see Illustration 12)

• Utilization gauge (see Illustration 13)

• Utilization scales for key species (see Illustration 13)

• Tape measure or ruler

• Additional equipment needed to prepare utilization scales:

- Clipping shears

- Thread

- Paper trimmer (for clipping plants into segments)

- Paper sacks

- Spring scale calibrated in tenths of grams

- Graph paper

- Blank card for utilization gauge

d Training This method does not require intensive training for field application,

although examiners must be able to identify the plant species. Examiners need

to know how to measure and record the height of grazed and ungrazed plants,

determine the utilization of individual plants from the gauge, and calculate the

average utilization by key species (see Section III.D.9).

e Establishing Studies Careful establishment of studies is a critical element in

obtaining meaningful data. Select key species and determine the number,

length, and location of the transects (see Section III.B.7).

(1) Collect data using several pilot transects to determine the number of

transects needed and the number of observations to be made on each

transect. These data are needed to determine if a statistically valid sample

has been collected (see Section III.B.7).
METHODS—HERBACEOUS REMOVAL—Height-Weight

90

(2) At the beginning of each study, determine the transect bearing and distance

between observation points. Select a prominent distant landmark such as a

large tree, rocky point, etc., that can be used as the transect bearing point.

(3) Plot the transects on detailed management unit maps and/or aerial photos

(see beginning of Section III).

(4) Permanently mark the location of each study with a reference post and

study location stake (see beginning of Section III).

(5) Number studies for proper identification to ensure that the data collected can

be positively associated with specific studies on the ground (see Appendix B).

(6) Document the location and other pertinent information concerning the

study on the Study Location and Documentation Data form (see beginning

of Section III and Appendix A).

f Sampling Process Sample ungrazed and grazed plants encountered along a

transect to determine the average ungrazed plant height and the average percent

utilization. To secure reliable utilization determinations, it is essential to measure heights for an adequate number of ungrazed and grazed plants. The greater

the variation in utilization between plants, the more plants required to determine

the average utilization.

(1) Measuring plant heights

(a) Best results are obtained by placing the measuring tape or ruler in the

center of the bunch or turf circle, rather than along one side. The tape

or ruler should not be forced down into the crown but should rest

firmly on the cushioned portion of the plant.

(b) Where rhizomatous/sod-forming grasses or grasslike plants are the key

species, use a circle of turf 2 inches in diameter as one plant.

(2) Sampling plants

(a) At each interval along the transect, select the plant of the key species

(seedlings excepted) nearest the toe and measure the height of the

plant to the nearest 1/4 inch. If plants are not evenly grazed, determine

the average stubble height.

(b) If the selected plant has not been grazed, record the height for that

sample in the Ungrazed Height Column on the Height-Weight form

(see Illustration 12).

(c) If the selected plant has been grazed, record the height for that sample in the

Grazed Height Column on the Height-Weight form (see Illustration 12)

(d) Measure at least 20 ungrazed plants to obtain a reliable cross section of

ungrazed plant heights. If a sufficient number of ungrazed plants is

not encountered along the transect, it may be necessary to extend the

transect or add more transects to the baseline (measuring both grazed
91

METHODS—HERBACEOUS REMOVAL—Height-Weight

and ungrazed plants) to pick up the additional ungrazed plant heights.

In some cases, it may be necessary to select, in a subjective manner,

ungrazed plants on an adjacent area to determine average ungrazed

plant height.

(e) Use only one kind of plant. When 80 percent or more of the plants

measured produce culms or when 80 percent or more are without

culms, the remaining 20 percent or less may be disregarded without

great error.

(f) When a combination occurs with 80 percent or more culm-producing

plants, and a plant lacking culms is encountered nearest the sampling

point, measure the nearest culm-producing plant of the species.

Corresponding procedures should be followed when the kind of plant

selected is without culms and a culm-producing plant is encountered.

These two combinations are those most commonly encountered in the

field.

(g) When approximately equal numbers of culm and culmless plants

occur, measure plants of both kinds. The measurements for the plants

with culms should be marked or kept separate on the form. Be sure to

use appropriate ungrazed heights and the correct utilization scales for

plants with and without culms.

g Calculations Calculate the percent utilization as follows:

(1) Divide the total of the ungrazed plant heights by the number of ungrazed

plants sampled to calculate the average ungrazed plant height.

(2) Determine the percent utilization of the key species with the gauge by

calculating the average plant heights of all the grazed and ungrazed plants.

The sliding card in the gauge is pulled out of the envelope until the utilization scale for the key species appears in the window. The dial is then

turned so that the number representing the previously calculated average

ungrazed height is set at the arrow designated “Average Ungrazed Height”.

The percent utilization may then be read on the scale in the window opposite the number on the dial representing the average height of grazed plants.

The utilization scale on the sliding card must fit the species being sampled

(see Illustration 13). Utilization on individually sampled plants can be

calculated by using the measured stubble height instead of the average

height of the grazed plants. Use the culmless curve for the key species when

seasonal utilization studies are conducted on early growth of the plants.

(3) Calculate the average utilization for a key species by totaling the percent

utilization for the individual sampled plants and dividing by the number of

sampled plants of that species.

(4) Record the average height of ungrazed plants, percent utilization of individual

sampled plants, and average percent utilization for the key species on the

Height-Weight form (see Illustration 12).
METHODS—HERBACEOUS REMOVAL—Height-Weight

92

h Preparing Utilization Scales Utilization scales used with the utilization

gauge are prepared from height-weight curves developed for individual grass

and grasslike species. Previously prepared utilization scales must be checked to

see whether or not these scales fit the species on the rangeland where they will

be used (See Illustration 13, pages 2, and 3). Where existing utilization scales

do not fit, new scales will have to be prepared. Scales for a number of species

are included on the same card.

(1) Developing height-weight curves Develop height-weight curves by collecting plants of a given species and determining the height—weight relationship for that species. The curve for any given species must be checked for

variation between range sites and climatic regions. It is necessary to develop separate curves for culm-producing plants and culmless plants when

a species only sporadically produces culms.

(a) Sampling plants. Sample at least ten plants of a given species. Select

only those plants which have reached maximum growth.

- At each interval along a pace transect, choose the ungrazed plant of

the given species nearest the toe. Use 1 square inch as a unit area

for sod-forming species and a comparable number of stems as a unit

area for single stem species.

- Remove all old leaves and stems of previous year’s growth.

- Clip the plant to within 1/4 inch of the ground.

- Wrap the clipped plant with thread from base to top to retain all

leaves and culms in their natural position.

- Separate the plants with culms from plants without culms and

consider each as a separate sample.

- Measure heights of clipped plants to the nearest inch and determine the average height.

- Calculate the number of plants that must be sampled to determine

average height with a standard error of + 3 to 5 percent at the 95

percent confidence level (Barrett and Nutt 1979, Freese 1962).

- Sample additional plants, if necessary.

- Measure the maximum height of each plant.

- Clip the top 10 percent by height of each plant and place the

clippings in a paper sack labeled 0 to 10 percent. Clip additional

height segments in 10 percent increments and place clippings in

appropriately labeled sacks—11 to 20 percent, 21 to 30 percent, 31

to 40 percent, 41 to 50 percent, 51 to 60 percent, 61 to 70 percent,

71 to 80 percent, 81 to 90 percent, and 91 to 100 percent. A large

paper trimmer with a guide to hold the plants in their proper
93

METHODS—HERBACEOUS REMOVAL—Height-Weight

position on the platform may be used to clip plants into segments.

Label the sacks to show species, date, and location. Place a given

height segment for all plants of a species collected in one paper sack.

- Dry the clippings until a final dried weight is achieved. Leave

clippings in the paper sacks for drying

(b) Determining height-weight relationships.

- Weigh and record the dry weight for each of the ten height segments to the nearest tenth of a gram. Subtract sack weight before

recording the dry weight of each height segment (see Illustration 14).

- Total the dry weight of the ten height segments and record the total

dry weight of the collected plants (see Illustration 14).

- Record the cumulative dry weight for each segment. This includes

the weight of the segment plus the weights of all preceding segments starting from the top of the plant (see Illustration 14).

- Calculate the cumulative percent height and weight removed at

each height segment by dividing the cumulative height or weight

for each segment by the total height or weight and multiplying by

100 (see Illustration 14).

- Plot the cumulative percent height removed against the cumulative

percent weight removed on graph paper. The resulting curve

portrays the height removed-weight removed relationship for the

species (see Illustrations 14 and 15).

(2) Transferring data from curves to scales Transfer the height-weight relationship data portrayed on the height-weight curve to a utilization scale for

use in the utilization gauge. The following text and Illustration 16 present

a situation where the average height of ungrazed plants is 10 inches.

(a) Turn the dial on the utilization gauge so that 10 inches is set at the

arrow designated “Average Ungrazed Height.” With the dial set at 10,

each inch increment from 9 to 0 on the dial represents 10 percent of

the height (see Illustration 16).

(b) Slide a blank card into the utilization gauge.

(c) Use the height-weight curve to determine the percent height that

would be removed when 10 percent, 20 percent, etc., of the weight is

removed (see Illustrations 15 and 16).

(d) From the height-weight curve, observe that for 10 percent of the

weight to be removed, 46 percent of the height must be removed

from the top of the plant. This means that 54 percent of the plant

height remains, or 5.4 inches of a 10-inch plant. Find the 5.4-inch

point on the circular dial, extend a horizontal line to the blank card,
METHODS—HERBACEOUS REMOVAL—Height-Weight

94

and write a “10” on the card (to show 10 percent utilization). Continue

this procedure for 20 percent weight removed, 30 percent weight

removed, etc., until all the points are plotted on the card.

(3) Documenting scale preparation For each utilization scale prepared,

maintain a record of the species, the data used to prepare the scale, the

date the scale was prepared, and the areas of applicability.

i Data Analysis Calculate confidence intervals for both ungrazed and grazed

plant heights.

j References

Barrett, James P. and Mary E. Nutt. 1979. Survey sampling in the environmental sciences: a computer approach. COMPress, Inc., Wentworth, N.H. 319

p.

Freese, Frank. 1962. Elementary forest sampling. U.S. Dept. of Agr., For. Ser.,

Agr. Handbook No. 232. 91 p.

Gierisch, Ralph K. 1967. An adaptation of the grazed plant method for estimating utilization of Thurber fescue. J. Range Manage. 20:108-111.

Heady, Harold F. 1950. Studies on bluebunch wheatgrass in Montana and

height-weight relationships of certain range grasses. Ecol. Monogr. 20:55-

81.

Lommasson, T. and Chandler Jensen. 1938. Grass volume tables for determining range utilization. Science 87:444.

———. 1943. Determining utilization of range grasses from height-weight

tables. J. Forestry 41:589-593.

McDougald, Neil K. and Richard C. Platt. 1976. A method of determining

utilization for wet mountain meadows on the summit allotment, Sequoia

National Forest, California. J. Range Manage. 29:497-501.

National Academy of Sciences/National Research Council. 1962. Basic problems and techniques in range research. NAS/NRC Publ. 890. 341 p.

Pechanec, J.F. and G.D. Pickford. 1937b. A weight-estimate method for the

determination of range or pasture production. J. Amer. Soc. Agron.

29:894-904.

U.S. Department of Interior Bureau of Land Management. 1984. Rangeland

Monitoring - Utilization Studies, TR4400-3.
95

METHODS—HERBACEOUS REMOVAL—Height-Weight

Illustration 12

Study Number Date Examiner

Allotment Name & Number Pasture

Kind and/or Class of Animal Period of Use

Key Species

%

Utilization Ungra Graze

Height

No %

Utilization Ungra Graze

Height

No %

Utilization Ungra Graze

Height

No

Ungra Graze

Height

No %

Utilization

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Total Height of

Ungraz. Plants

Number of

Sampled Plants

Total % Util. for

All Sampled Plants

Total Height of

Ungrazed Plants

Number of

Ungrazed Plants

Average

Ungrazed

Plant

Height

= = Average

Utilization = =

Total Percent

Utilization

Number of

Sampled Plants

Notes (use other side or another page, if necessary)

Culm Culmless

Height-Weight

Page of

97

METHODS—HERBACEOUS REMOVAL—Height-Weight

Illustration 13

AN INSTRUMENT FOR

MEASURING THE

UTILIZATION OF GRASSES

AVERAGE UNGRAZED HEIGHT

U.S. FOREST SERVICE, ROCKY MOUNTAIN FOREST AND RANGE EXPERIMENT STATION

Front Side of Gauge

UTILIZATION

GAUGE

Back Side of Gauge

0

30 40 20 15

10 8 7

6 5.0

4.0

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C 1980 AMERICAN Slide-Chart Corp, Wheaton, Ill 60187 Printed in U.S.A.

INSTRUCTIONS FOR USE

A. Measure and record by species the heights of ungrazed plants: total, and divide by the number to

determine average ungrazed height. If sufficient ungrazed plants do not occur on sampling area,

measure plants adjacent to it.

For seedstalk producing (culm) plants, measure tallest seedstalk to nearest 1"; non-stalk producing

(culmless) plants, the tallest leaf heights to 1/2".

B. Measure and record by species the heights of ungrazed plants. If plants are not cropped off evenly,

measure average stubble height of each plant.

Measure all grazed plants to nearest 1/4".

C. Pull slide out of envelope until scale for species concerned appears in window.

D. Turn dial until average ungrazed height determined in "A" appears opposite Arrow so designated.

E. On dial find grazed heights recorded in "B" and opposite on slide read percent utilization for each

plant.

F. Repeat operation for each grazed height, total utilization percentages and divide by the total number

of plants. This gives average percentage utilization.

Utilization Gauge
METHODS—HERBACEOUS REMOVAL—Height-Weight

98 Illustration 13 page 2

Front

LYCURUS PHLEOIDES Wolftall

HILARIA MUTICA Tobosa

HILARIA BELANGERI Curley mesquite

HETEROPOGON CONTORTUS Tanglehead

KOELERIA CRISTATA

FESTUCA IDAHOENSIS

DESCHAMPSIA CAESPITOSA

CAREX FILFOLIA

CAREX DOUGLASII

CALAMAGROSTIS RUBESCENS

BOUTELOUA GRACILIS

BOUTELOUA CURTIPENDULA

ANDROPOGON FURCATUS

AGROPYRON SPICATUM

AGROPYRON SMITHII

AGROPYRON CRISTATUM

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These utilization scales must be checked to see whether or not they fit the

species on the rangeland where they will be used.

Front side of card

Back side of card

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Back STIPA RICHARDSONI STIPA COMATA STIPA COLUMBIANA POA SECUNDA KOELERIA CRISTATA FESTUCA IDAHOENSIS DESCHAMPSIA CAESPITOSA CAREX FILFOLIA CAREX DOUGLASII CALAMAGROSTIS RUBESCENS BOUTELOUA GRACILIS BOUTELOUA CURTIPENDULA ANDROPOGON FURCATUS

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METHODS—HERBACEOUS REMOVAL—Height-Weight

Illustration 13 page 3

Front

STIPA RICHARDSONI

STIPA COMATA

STIPA COLUMBIANA

POA SECUNDA

KOELERIA CRISTATA

FESTUCA IDAHOENSIS

DESCHAMPSIA CAESPITOSA

CAREX FILFOLIA

CAREX DOUGLASII

CALAMAGROSTIS RUBESCENS

BOUTELOUA GRACILIS

BOUTELOUA CURTIPENDULA

ANDROPOGON FURCATUS

AGROPYRON SPICATUM

AGROPYRON SMITHII

AGROPYRON CRISTATUM

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FESTUCA IDAHOENSIS 3" to 5" "Culmless"

"Culmless"

"Culmless"

"Culmless"

"Culmless"

"Culmless"

FESTUCA IDAHOENSIS 5" and Up

CALAMAGROSTIS RUBESCENS

ANDROPOGON FURCATUS

AGROPYRON SPICATUM

AGROPYRON SMITHII

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Utilization Gauge (concluded)

These utilization scales must be checked to see whether or not they fit the

species on the rangeland where they will be used.

Front side of card

Back side of card
METHODS—HERBACEOUS REMOVAL—Height-Weight

100 Illustration 14

Example of Data Set for Determining Height-Weight Relationships Used in Preparing

Utilization Scales

Height Dry Weight by Cumulative Cumulative Cumulative

Segment Height Segment Dry Weight % Height % Weight

(percent) (grams) (grams) Removed Removed

0-10 2.8 2.8 10 0.9

11-20 5.6 8.4 20 2.6

21-30 7.0 15.4 30 4.8

31-40 8.4 23.8 40 7.4

41-50 15.4 39.2 50 12.2

51-60 22.1 61.3 60 19.0

61-70 38.3 99.6 70 30.9

71-80 54.6 154.2 80 47.8

81-90 75.7 229.9 90 71.3

91-100 92.6 322.5 100 100.0

322.5

Example of Data Set
101

METHODS—HERBACEOUS REMOVAL—Height-Weight

Illustration 15

0

0 10

Percent of Height Removed

Percent of Weight Removed

20 30 40 50 60 70 80 90 100

10

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100

Scientific Name and Code -

Common Name -

Culm Producing or Culmless Plants -

Allotment Name and Number -

Resource Area -

District -

Date -

Example of Height-Weight Curve Used for Preparing Utilization Scales
METHODS—HERBACEOUS REMOVAL—Height-Weight

102 Illustration 16

10%

20%

30%

40%

50%

60%

70%

80%

90%

95%

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0% 100

Utilization Scale The percent height removed when

10%, 20%, etc., of the weight

is removed is determined from

the height-weight curve.

(See Illustration 15.)

Scientific Name and Code -

Common Name -

Date -

Percent

Height

Removed

Average Ungrazed Height

Y Mountain Forest and Range Experiment

20 15 10 8 7 6 5.0 4.0

3.0

2.0 1.0

3/4

1/2

1/4

30

Method for Transferring Data from Height-Weight Curves to Utilization Scales

Percent

Height

Removed

Percent

Height

Remaining
103

METHODS—HERBACEOUS REMOVAL—Actual Weight

5. Actual Weight Method The Actual Weight Method involves separately clipping

and weighing current year’s growth from grazed and ungrazed plants along a

transect. Only available forage plants are clipped along the transect. The difference

between weights represents the amount of forage consumed by animals or otherwise destroyed during the period of use. Where utilization levels are such that few

ungrazed plants are available, cages within the pasture or similar reference areas in

ungrazed pastures are required to obtain an estimate of the ungrazed weight.

a Areas of Use This method is best adapted to clearly defined growth forms

such as bunchgrasses. It is not recommended for areas where shrubs or rhizomatous plants are the key species. It can be used on sodforming grasses if a

small quadrat, 2 or 3 inches square, is used to delineate a unit.

b Advantages and Limitations The method is simple, accurate, and reduces

personal error caused by estimation of utilization levels found in other methods.

The actual weight method is restricted primarily to bunch and sod-forming

grasses. This method is best adapted to short duration grazing on small pastures,

which reduces the effects of regrowth.

c Equipment

• Study Location and Documentation Data form (see Appendix A)

• Actual Weight form (see Illustration 17)

• Frames to delineate quadrats (if necessary).

• Clipping shears

• Paper sacks

• Spring scale, calibrated in grams

• Cages as required (see Appendix E)

d Training Little training is required for this method. Examiners must be able

to identify the plant species. Training is limited to clipping and weighing,

grazed and ungrazed plants, separating out the current year’s growth from

residue, and recording the weights.

e Establishing Studies Careful establishment of studies is a critical element in

obtaining meaningful data. Select key species and determine the number,

length, and location of the transects (see Section III.B.7). Place cages within the

study site, as required, to obtain a representative sample of the ungrazed weight

of all key species.

(1) Collect data using several pilot transects to determine the number of

transects needed and the number of observations to be made on each

transect. These data are needed to determine if a statistically valid sample

has been collected (see Section III.B.7).

(2) At the beginning of each study, determine the transect bearing and distance

between observation points. Select a prominent distant landmark such as a

large tree, rocky point, etc., that can be used as the transect bearing point.
METHODS—HERBACEOUS REMOVAL—Actual Weight

104

(3) Plot the transects on detailed management unit maps and/or aerial photos

(see beginning of Section III).

(4) Permanently mark the location of each study with a reference post and

study location stake (see beginning of Section III).

(5) Number studies for proper identification to ensure that the data collected

can be positively associated with specific studies on the ground

(see Appendix B).

(6) Document the location and other pertinent information concerning the

study on the Study Location and Documentation Data form (see beginning

of Section III and Appendix A).

f Sampling Process After examiners are trained, proceed with the collection of

utilization data.

(1) Select two paper sacks for each key species; one is marked “grazed” and the

other “ungrazed.”

(2) At each interval along the transect, select the plant of the key species that

is nearest the toe and clip it to ground level or some other easily identifiable

level. Collection of grazed and ungrazed plants as they occur along the

transect is extremely important. Only the plants collected along the

transect are used in calculating utilization. Plants clipped from cages or

adjoining representative areas (see Section (8) below) used to calculate the

average ungrazed weight are not used in the percent utilization calculations.

(3) Place the plant, grazed or ungrazed, in the appropriate sack and mark a

tally on the outside of the sack or on a tally sheet. For example, a grazed

plant is clipped and placed in the sack marked “grazed”. The tally is made

so the number of plants in each sack is known.

(4) Clip plants along the transect until there are at least 25 plants (or some

other predetermined number) in each of the grazed and ungrazed sacks.

Do not discontinue clipping one kind (grazed or ungrazed) of plant when

extending the transect to satisfy the minimum quota for the other kind of

plant. The grazed and ungrazed sacks will probably not contain the same

number of plants. (For example, if the grazed sack contains 25 plants and

the ungrazed sack contains 20 plants, continue to clip grazed and ungrazed

plants encountered along the transect until the ungrazed sack contains 25

plants. In this example, the grazed sack will probably contain more than

25 plants when the minimum quota of ungrazed plants is finally met.)

(5) Determine the number of grazed and ungrazed plants that were clipped.

(6) Separate out the current year’s growth from previous years’ residue and

then weigh each sack separately to determine the weights of current

growth for the grazed and ungrazed plants.

(7) Record the numbers and weights on the Actual Weight form

(see Illustration 17).
105

METHODS—HERBACEOUS REMOVAL—Actual Weight

(8) If enough ungrazed plants cannot be found, clip ungrazed plants from

either within the cages placed within the study site, along a transect in an

adjoining area, in an ungrazed pasture within the management unit, or in

another ungrazed area in the vicinity to obtain the average weight of

ungrazed plants. These sites must be as similar as possible (vegetation type,

soil, etc.) to the area in which the study is being conducted. It is preferable

that dry weight be determined and used in the calculations of percent

utilization if an extended period of time will elapse between collection of

grazed plants and the collection of ungrazed plants.

g Calculations Calculate the percent utilization as follows:

(1) Step 1. Calculate the average weight of ungrazed plants.

Total weight of ungrazed plants

Total number of ungrazed plants = Average weight of ungrazed plants

(2) Step 2. Calculate the total weight of all clipped plants as if none had been

grazed.

Total number of plants clipped along Average weight Total weight of all

the transect (both grazedand ungrazed) x of ungrazed plants = clipped plants as if

none had been grazed

(3) Step 3. Calculate the percent of total production (weight) remaining.

Total weight of clipped plants

(grazed and ungrazed)

Total weight of all clipped x 100 = Percent of total production (weight) remaining

plants as if none had been grazed

(4) Step 4. Calculate the percent utilized.

100% - Percent of total production (weight) remaining = Percent utilized

(5) Step 5. Record the percent utilization on the Actual Weight form

(see Illustration 17).

h Data Analysis Calculate confidence intervals around the average estimated

percent utilization.

i References

Heady, Harold F. 1949. Methods of determining utilization of range forage. J.

Range Manage. 2:53-63.

U.S. Department of Interior Bureau of Land Management. 1984. Rangeland

Monitoring - Utilization Studies, TR4400-3.
METHODS—HERBACEOUS REMOVAL—Actual Weight

106 Illustration 17

Study Number Date Examiner

Allotment Name & Number Pasture

Kind and/or Class of Animal Period of Use

Key Species

Plants

Number

of

Plants

Total

Weight*

(grams)

Totals

Ungrazed

Grazed

Notes (use other side or another page, if necessary)

See other side for explanation of the steps for calculating

percent utilization.

Step 1

Step 2

Step 4

Step 3

Grams per ungrazed plant

Grams (weight of all plants as if

none had been grazed)

% Utilization

% of weight remaining

100% –

x

x 100

=

=

=

=

Key Species

Plants

Number

of

Plants

Total

Weight*

(grams)

Totals

Ungrazed

Grazed

Notes (use other side or another page, if necessary)

See other side for explanation of the steps for calculating

percent utilization.

Step 1

Step 2

Step 4

Step 3

Grams per ungrazed plant

Grams (weight of all plants as if

none had been grazed)

% Utilization

% of weight remaining

100% –

x

x 100

=

=

=

=

* Minus the weight of the sack

Actual Weight

Page of
107

METHODS—HERBACEOUS REMOVAL—Actual Weight

Actual Weight Calculations

Calculate Percent Utilization of Ungrazed Plants as Follows:

Step 1. calculate the average weight of ungrazed plants.

Total weight of ungrazed plants = Average weight of ungrazed plants

Total number of ungrazed plants

=

Step 2. calculate the total weight of all clipped plants as if none had been grazed.

Total number of plants clipped x Average weight of = Total weight of all clipped plants

(both clipped and ungrazed) ungrazed plants as if none had been grazed

x =

Step 3. calculate the percent of total production (weight) remaining.

Total weight of clipped plants (grazed and ungrazed) x 100 = Percent of total production

 Total weight of all clipped plants as if none had weight remaining

been grazed

x 100 =

Step 4. calculate the percent utilization.

100% - Percent to total production (weight) remaining = Percent utilized

100% - =

Notes:

Illustration 17 page 2

109

METHODS—HERBACEOUS REMOVAL—Grazed Class

6. Grazed-Class Method The Grazed-Class Method uses photo guides of key

species to make utilization estimates. These estimates reflect herbage removed but

also show herbage remaining.

a Areas of Use This method is adapted for use on perennial grass, perennial

grass-forb, and grass-shrub rangelands where the key species are either bunch or

rhizomatous/sod-forming grass or grasslike species. It is designed for use after

the plants have achieved full seasonal growth.

b Advantages and Limitations

(1) This method is rapid and easy to learn and use. It can be used by livestock

operators and examiners to give consistent and accurate estimates of

utilization. The mathematics involved are simple.

(2) In poor growth years when plants do not mature, the guides will not

distinguish between use and no-growth.

(3) The difficult job is developing photo guides based on average plants on a

typical site that have a good photo-height-weight representation. One

guide, properly developed for a given species and a typical site, can be used

on all sites over a fairly broad area (e.g., the Southwest) in good and bad

production years without serious error. The guides serve as standards of

comparison that promote consistency in estimates.

(4) The method tends to reduce errors caused by variability in height growth,

one of the major sources of error in height-weight methods. In making

estimates of utilization by the grazed-class method, the growth form of the

plant is used as the primary guide and visual adjustments for differences in

height can easily be made by the examiner. (Schmutz et al. 1963)

(5) Another advantage is that, while the estimate of utilization is based on

forage removed, each grazed-class shows both the degree of use and the

amount of herbage remaining. (Schmutz et al. 1963)

(6) The method facilitates estimation of irregular grazing of plants. Although

the guide plants are clipped to a certain height and may not represent the

normal pattern of grazing, they do provide a visual picture of the volume

by grazed classes and serve as a guide to the examiner in estimating irregular use of the plant, such as occurs in side-trimming of leaves or partial

grazing of seed stalks. This requires judgment on the part of the examiner

but accuracy increases with experience and errors are off-setting. The

method is thus largely free from personal bias yet allows for experienced

judgment on grazing use of irregularly grazed plants. (Schmutz et al. 1963)

(7) A minimum of 1 to 2 hours experience by examiners regardless of prior

experience will produce uniform accuracy. (Schmutz et al. 1963)

c Important Considerations

(1) Errors can be encountered because of variations in plant growth between

sites and ecoregions. Photographic guides should therefore be checked
METHODS—HERBACEOUS REMOVAL—Grazed Class

110

with growth curves of local plants. New guides should be prepared if the

existing photo guides do not correspond to the growth curves.

(2) Several guides may need to be developed for each key species to match

wide year-to-year or site-to-site variations in growth form. Development

of guides based on averages of local plants within a given region will reduce

the possibility of variation that might result from using curves developed

for broad geographic regions or between states. (Gierisch 1967)

d Equipment

• Study Location and Documentation Data form (see Appendix A)

• Grazed-Class form (see Illustration 18)

• Photo guides (see Illustration 19)

• Tally counter (optional)

• Additional equipment needed to develop photo guides:

- Clipping shears

- Paper sacks

- Spring scale calibrated in tenths of grams

- Graph paper

e Training Minimal training of examiners is needed to use this method. Examiners must be able to identify the plant species. The major problem with

inexperienced examiners, and examiners who have not used the method for

some time, is underestimation of use on more heavily grazed plants.

f Establishing Studies Careful establishment of studies is a critical element in

obtaining meaningful data. Select key species and determine the number,

length, and location of the transects (see Section III.B.7).

(1) Collect data using several pilot transects to determine the number of

transects needed and the number of observations to be made on each

transect. These data are needed to determine if a statistically valid sample

has been collected (see Section III.B.7).

(2) At the beginning of each study, determine the transect bearing and distance

between observation points. Select a prominent distant landmark such as a

large tree, rocky point, etc., that can be used as the transect bearing point.

(3) Plot the transects on detailed management unit maps and/or aerial photos

(see beginning of Section III).

(4) Permanently mark the location of each study with a reference post and

study location stake (see beginning of Section III).

(5) Number studies for proper identification to ensure that the data collected

can be positively associated with specific studies on the ground

(see Appendix B).

(6) Document the location and other pertinent information concerning the

study on the Study Location and Documentation Data form (see beginning

of Section III and Appendix A).
111

METHODS—HERBACEOUS REMOVAL—Grazed Class

g Sampling Process

(1) At each interval along the transect, select the plant(s) of the key species

(seedlings excepted) nearest the toe.

(2) Compare the sample plant(s) with the photo guides for that species and

classify according to one of six grazed-classes representing 0, 10, 30, 50,

70, or 90 percent use (see Illustration 19).

(3) Base the estimates of utilization on growth form of the plant. Variations in

height growth due to site characteristics and seasonal precipitation can be

disregarded since variations in height are automatically adjusted for by the eye.

(4) Record the estimates by dot count for each grazed class on the GrazedClass form (see Illustration 18).

(5) For bunch grasses, make estimates on individual plants.

(6) For rhizomatous/sod-forming key species, make estimates on 6-, 8-, 10-, or

12-inch square quadrats along the transect.

h Calculations Calculate the percent utilization as follows:

(1) Convert the dot count to the number of plants sampled by grazed-class.

(2) Multiply the number of plants sampled in each grazed-class by the grazedclass percent.

(3) Total the products for all classes.

(4) Divide the sum by the total number of plants observed on the transect.

(5) Record the average percent utilization on the Grazed-Class form

(see Illustration 18).

i Developing Photo Guides Photo guides must be developed that have a close

relationship between the grazed-class percentages of the guide and the heightweight curve of the plant photographed. Guides are developed as follows:

(1) When plants of a given species have reached full growth, sample 5 to 10

representative plants from a typical site. For bunchy species, sample

individual plants. For rhizomatous/sod-forming species, sample plants

from a 6-, 8-, 10-, or 12-inch square quadrat.

(2) Beginning at the top of the plant, clip 4- to 10-inch segments from the top

portion and 2-inch segments from the lower portion of each plant (see

Illustration 20). Place each segment in an individual paper sack. Label the

sacks to show species, plant number, segment number, segment length,

date, and location. Keep the clippings from each plant separate. Make all

height measurements from the base of the plant. For bunchgrasses, use the

center of the root crown.
METHODS—HERBACEOUS REMOVAL—Grazed Class

112

(3) Oven dry and carefully weigh each plant segment to the nearest tenth of a

gram. Subtract sack weight before recording the dry weight of each segment

(see Illustration 20).

(4) Beginning at the top of the plant, record the cumulative dry weight for

each segment. This includes the weight of the segment plus the weights of

all preceding segments (see Illustration 20).

(5) Calculate the cumulative percent weight for each segment by dividing the

cumulative dry weight for each segment by the total dry weight and

multiplying the result by 100 (see Illustration 20).

(6) Beginning at the base of each plant, record the cumulative height remaining

by segment. This includes the combined length of all preceding segments

(see Illustration 20).

(7) Determine the average height of the clipped plants.

(8) Adjust the height remaining of each individual plant to average plantheight remaining with the following formula:

Adjusted individual Total height of average plant Height remaining of

plant-height remaining = Total height of individual plant x individual plant

(9) Plot the cumulative percent weight of the individual plants against the

adjusted individual plant-height remaining on graph paper (see Illustration

21). Use the lower left-hand corner as zero on both scales and plot 5 or 6

clipped plants of a given species on the same graph.

(10) Determine the average plant height for the six grazed-class percentages

(percent weight removed), 0, 10, 30, 50, 70 and 90 percent, from the

height-weight curves on the graph (see Illustration 21).

(11) Return to the field and select 4 to 6 average plants to be used in making a

photo guide for the given species. Use the grazed-class heights read from

the average curve on the graph to determine the heights at which to clip

the plants to be photographed using the formula:

Grazed-class

Clipping height of plant = Total height of plant to be photographed x height of

 to be photographed Total height of average plant average plant

(12) Photograph each plant in sequence at the unclipped height and at heights

representing 10, 30, 50, 70, and 90 percent of the weight removed. Clip

the last increment to ground level or as close as possible. For bunchgrasses,

clip to the root crown.

(13) Sack the clippings separately and dry them in an oven. Label the sacks to

show species, plant number, clipped height, grazed-class percentage, date,

and location.
113

METHODS—HERBACEOUS REMOVAL—Grazed Class

(14) Determine if the curve of at least one of the photographed plants closely

matches the average curve on the graph. In addition, determine if the

cumulative weight percentages for the various clipped heights of that plant

closely match the grazed-class percentages (within 2 or 3 percentage

points). If a close match is obtained, trim the photos and put them on a

grazed-class photo guide background (see Illustration 19). If not, repeat

the photographing of average plants until a close representation is obtained.

(15) For each photo guide prepared, maintain a record of the species, the data

used to prepare the guide, the date the guide was prepared, and the areas

of applicability.

j Established Photo Guides The following are sources of existing photo guides.

(1) University of Arizona, Cooperative Extension Service and Agricultural

Experiment Station, Tucson Arizona 85721. Bulletin A-73.

(2) University of Idaho, College of Forestry, Wildlife and Range Science,

Moscow, Idaho 83843. Station bulletin 54.

(3) Montana State University. Forage Use - A Tool for Planning Range

Management. Extension Service. July 1988.

(4) Kinney and Clary. 1994. A Photographic Utilization Guide for Key Riparian

Graminoids. USFS GTR-308.

k Data Analysis Calculate confidence intervals around the average Estimated

percent utilization.

l References

Gierisch, Ralph K. 1967. An adaptation of the grazed plant method for

estimating utilization of Thurber fescue. J. Range Manage. 20:108-111.

Schmutz, Ervin M. 1971. Estimation of range use with grazed-class photo

guides. Coop. Extension Service and Agr. Exp. Sta., Univ. of Ariz., Tucson,

AZ, Bull. A-73. 16 p.

Schmutz, E.M., G.A. Holt, and C.C. Michaels. 1963. Grazed class method of

estimating forage utilization. J. Range Manage. 16:54-60.

U.S. Department of Interior Bureau of Land Management. 1984. Rangeland

Monitoring - Utilization Studies, TR4400-3.
METHODS—HERBACEOUS REMOVAL—Grazed Class

114 Illustration 18

Study Number Date Examiner

Allotment Name & Number Pasture

Kind and/or Class of Animal Period of Use

 Key Species Key Species Key Species Grazed

Class

Percents

(P) Dot

Count

Dot

Count

Dot

Count

No by

Class

(C)

No by

Class

(C)

No by

Class

(C)

No X

Class %

(C) (P)

No X

Class %

(C) (P)

No X

Class %

(C) (P)

0

10

30

50

70

90

Totals Totals Totals

∑(CP)*

∑C = avg.

util. ===

Grazed Class

Page of

Notes (Use other side or another page, if necessary)

* Where C = the number of plants within each class (C column), P = the grazed-class percentages (P column),

 and ∑ = the summation symbol.

METHODS—HERBACEOUS REMOVAL—Grazed Class

116 Illustration 19

Blue

Grama

Percent

Utilization

SideOats

Grama

Percent

Utilization

Grazed Class Method Photo Guides
117

METHODS—HERBACEOUS REMOVAL—Grazed Class

Illustration 20

Example of Data Set for Determining Height-Weight Relationships

for Developing Photo Guides

Scientific Name & Code

Species Date

Segment Dry Weight Cumulative Adjusted

Number Segment by Plant Cumulative Cumulative Height Height

(from top Length Segment Dry Weight Percent Remaining Remaining

down) (inches) (grams) (grams) Weight (inches) (inches)

- - - - 0 21.5 26.0

1 6.5 .9 .9 7.5 15.0 18.1

2 4.0 .9 1.8 15.0 11.0 13.3

3 3.0 .7 2.5 20.8 8.0 9.7

4 2.0 .7 3.2 26.7 6.0 7.3

5 2.0 .9 4.1 34.2 4.0 4.8

6 2.0 1.9 6.0 50.0 2.0 2.4

7 2.0 6.0 12.0 100.000 0 0

21.5 12.0
METHODS—HERBACEOUS REMOVAL—Grazed Class

118 Illustration 21

Example of Height-Weight Curve Used for Determining Average Plant Height

for the Six Grazed-Class Percentages on Photo Guides

Adjusted Plant Height (inches)

28

24 Height-Weight Curves

Average Curve Used to Develop

Photo Guides

20

16

12

8

4

0 20 40

Cumulative Percent Weight

60 80 100

0
119

METHODS—QUALITATIVE ASSESSMENT—Landscape Appearance

D. Qualitative Assessments - Landscape Appearance Method

(formerly the Key Forage Plant Method)

This technique uses an ocular estimate of forage utilization based on the general

appearance of the rangeland. Utilization levels are determined by comparing observations

with written descriptions of each utilization class.

a Areas of Use This method is adapted to areas where perennial grasses, forbs,

and/or browse plants are present and to situations where utilization data must

be obtained over large areas using only a few examiners.

b Advantages and Limitations This method is rapid and does not require

unused areas for training purposes. Estimates are based on a range (class) of

utilization rather than a precise amount. Different examiners are more likely to

estimate utilization in the same classes than to estimate the same utilization

percentages. One limitation of this technique is that the method can still result

in varying estimates because of different examiners. Another limitation is that

there is no way to assess the precision of the estimate because the estimates are

qualitative.

c Equipment

• Study Location and Documentation Data form (see Appendix A)

• Landscape Appearance form (see Illustration 22)

• Tally counter (optional)

d Training Personal judgment is involved in any estimation method. Estimates

are only as good as the training and experience of the examiners (see Section

III.D.9). The training described for the Ocular Estimate and Key Species

Methods often helps examiners using this method make the utilization class

estimations (see Section V.C.2 and 3). The examiners must be trained to

recognize the seven herbaceous or seven browse utilization classes using the

written class descriptions. Examiners must think in terms of the general appearance

of the rangeland at each observation point, rather than weight or height removed.

e Establishing Studies Careful establishment of studies is a critical element in

obtaining meaningful data. Note that it is not necessary to select key species or

to complete pilot studies, since statistical analysis is not possible under this method.

(1) At the beginning of each study, determine the transect bearing and distance

between observation points. Select a prominent distant landmark such as a

large tree, rocky point, etc., that can be used as the transect bearing point.

(2) Plot the transects on detailed management unit maps and/or aerial photos

(see beginning of Section III).

(3) Permanently mark the location of each study with a reference post and

study location stake (see beginning of Section III).

(4) Number studies for proper identification to ensure that the data collected

can be positively associated with specific studies on the ground

(see Appendix B).
METHODS—QUALITATIVE ASSESSMENT—Landscape Appearance

120

(5) Document the location and other pertinent information concerning the

study on the Study Location and Documentation Data form (see beginning

of Section III and Appendix A).

f Sampling Process After examiners are trained and have confidence in their

ability to judge utilization by utilization classes, proceed with the collection of

utilization data. At each observation point along the transect, estimate the

utilization class using the written description of the classes. In those cases

where part of a class description does not apply (example: percentage of

seedstalks remaining), judge utilization based on those parts of the description

that do apply. An observation point is the immediate area visible to examiners

when standing at a particular location along the transect. Record the estimates

by dot count by utilization class on the Landscape Appearance From

(see Illustration 22).

(1) Herbaceous utilization classes Seven utilization classes are used to show

relative degrees of use of herbaceous species (grasses and forbs). Each class

represents a numerical range of percent utilization. Estimate utilization

within one of the seven classes. Utilization classes are as follows:

(a) (0-5%). The rangeland shows no evidence of grazing use or negligible

use.

(b) (6-20%). The rangeland has the appearance of very light grazing. The

herbaceous forage plants may be topped or slightly used. Current

seedstalks and young plants are little disturbed.

(c) (21-40%). The rangeland may be topped, skimmed, or grazed in

patches. The low value herbaceous plants are ungrazed and 60 to 80

percent of the number of current seedstalks of herbaceous plants

remain intact. Most young plants are undamaged.

(d) (41-60%). The rangeland appears entirely covered as uniformly as

natural features and facilities will allow. Fifteen to 25 percent of the

number of current seedstalks of herbaceous species remain intact. No

more than 10 percent of the number of low-value herbaceous forage

plants are utilized. (Moderate use does not imply proper use.)

(e) (61-80%). The rangeland has the appearance of complete search.

Herbaceous species are almost completely utilized, with less than 10

percent of the current seedstalks remaining. Shoots of rhizomatous

grasses are missing. More than 10 percent of the number of low-value

herbaceous forage plants have been utilized.

(f) (81-94). The rangeland has a mown appearance and there are indications of repeated coverage. There is no evidence of reproduction or

current seedstalks of herbaceous species. Herbaceous forage species

are completely utilized. The remaining stubble of preferred grasses is

grazed to the soil surface.
121

METHODS—QUALITATIVE ASSESSMENT—Landscape Appearance

(g) (95-100). The rangeland appears to have been completely utilized.

More than 50 percent of the low-value herbaceous plants have been

utilized.

(2) Browse utilization classes Seven utilization classes show relative degrees

of use of available current year’s growth (leaders) of browse plants (shrubs,

half shrubs, woody vines, and trees). Each class represents a numerical

range of percent utilization. Estimate utilization within one of the seven

classes. Utilization classes are as follows:

(a) (0-5%). Browse plants show no evidence of grazing use or only

negligible use.

(b) (6-20%). Browse plants have the appearance of very light use. The

available leaders of browse plants are little disturbed.

(c) (21-40%). There is obvious evidence of leader use. The available

leaders appear cropped or browsed in patches and 60 to 80% of the

available leader growth of browse plants remains intact.

(d) (41-60%). Browse plants appear rather uniformly utilized and 40 to

60% of the available leader growth of browse plants remains intact.

(e) (61-80%). The use of the browse gives the appearance of complete

search. The preferred browse plants are hedged and some plant

clumps may be slightly broken. Nearly all available leaders are used

and few terminal buds remain on browse plants. Between 20 and 40%

of the available leader growth of browse plants remains intact.

(f) (81-94%). There are indications of repeated coverage. There is no

evidence of terminal buds and usually less than 20% of available leader

growth on browse plants remains intact. Some patches of second and

third years’ growth may be grazed. Hedging is readily apparent and

the browse plants are more frequently broken. Repeated use at this

level will produce a definitely hedged or armored growth form.

(g) (95-100). Less than 5% of the available leader growth on browse

plants remains intact. Some, and often much, of the more accessible

second and third years’ growth of the browse plants has been utilized.

All browse plants have major portions broken.

g Calculations Calculate the percent utilization as follows:

(1) Convert the dot count to the number of observations for each utilization

class.

(2) Multiply the number of observations in each utilization class times the

midpoints of the class intervals.

(3) Total the products for all classes.
METHODS—QUALITATIVE ASSESSMENT—Landscape Appearance

122

(4) Divide the sum by the total number of observations on the transect.

(5) Record the average percent utilization on the Landscape Appearance form

(see Illustration 22).

h Data Analysis Calculate confidence intervals around average estimated percent

utilization.

i References

Anderson, E. William and Wilbur F. Currier. 1973. Evaluating zones of utilization.

J. Range Manage. 26:87-91.

Heady, Harold F. 1949. Methods of determining utilization of range forage. J.

Range Manage. 2:53-63.

U.S. Department of Interior Bureau of Land Management. 1984. Rangeland

Monitoring - Utilization Studies, TR4400-3.
123

METHODS—QUALITATIVE ASSESSMENT—Landscape Appearance

Illustration 22

Study Number Date Examiner

Allotment Name & Number Pasture

Kind and/or Class of Animal Period of Use

No. X

Midmt.

(C)(M)

No. By

Class

(C)

Int

Mid

(M)

Class

Interval

Dot

Count

0-5%

6-20%

61-80%

81-94%

21-40%

41-60%

95-100%

Notes (use other side or another page, if necessary)

2.5

88

70

50

13

30

97.5

Totals

= ∑(CM)*

∑C

Avg.

Util.

(a) (0-5%). The rangeland shows no evidence of grazing or

negligible use.

(b) (6-20%). The rangeland has the appearance of very light

grazing. The herbaceous forage plants may be topped or

slightly used. Current seedstalks and young plants are little

disturbed.

(c) (21-40%). The rangeland may be topped, skimmed, or

grazed in patches. The low value herbaceous plants are

ungrazed and 60 to 80 percent of the number of current

seedstalks of herbaceous plants remain intact. Most young

plants are undamaged.

(d) (41-60%). The rangeland appears entirely covered as

uniformly as natural features and facilities will allow. Fifteen

to 25 percent of the number of current seedstalks of herbaceous species remain intact. No more than 10 percent of the

number of low-value herbaceous forage plants are utilized.

(Moderate use does not imply proper use.)

(e) (61-80%). The rangeland has the appearance of complete search. Herbaceous species are almost completely

utilized, with less than 10 percent of the current seedstalks

remaining. Shoots of rhizomatous grasses are missing. More

than 10 percent of the number of low-value herbaceous

forage plants have been utilized.

(f) (81-94). The rangeland has a mown appearance and

there are indications of repeated coverage. There is no

evidence of reproduction or current seedstalks of herbaceous

species. Herbaceous forage species are completely utilized.

The remaining stubble of preferred grasses is grazed to the

soil surface.

(g) (95-100). The rangeland appears to have been completely utilized. More than 50 percent of the low-value

herbaceous plants have been utilized.

=

Page of

Landscape Appearance

* Where C = The number of observations within each

class interval (C column),

M = the class interval midpoint (M column),

and ∑ = the summation symbol.
METHODS—QUALITATIVE ASSESSMENT—Landscape Appearance

124 Illustration 22 page 2

Browse Utilization Classes

(a) (0-5%). Browse plants show no evidence of use; or only negligible use.

(b) (6-20%). Browse plants have the appearance of very light use. The available

leaders of browse plants are little disturbed.

(c) (21-40%). There is obvious evidence of leader use. The available leaders appear

cropped or browsed in patches and 60 to 80% of the available leader growth of

browse plants remains intact.

(d) (41-60%). Browse plants appear rather uniformly utilized and 40 to 60% of the

available leader growth of browse plants remains intact.

(e) (61-80%). The use of the browse gives the appearance of complete search. The

preferred browse plants are hedged and some plant clumps may be slightly broken.

Nearly all available leaders are used and few terminal buds remain on browse plants.

Between 20 and 40% of the available leader growth of browse plants remains intact.

(f) (81-94%). There are indications of repeated coverage. There is no evidence of

terminal buds and usually less than 20% of available leader growth on browse plants

remains intact. Some patches of second and third years’ growth may be grazed.

Hedging is readily apparent and the browse plants are more frequently broken.

Repeated use at this level will produce a definitely hedged or armored growth form.

(g) (95-100). Less than 5% of the available leader growth on browse plants remains

intact. Some, and often much, of the more accessible second and third years’ growth

of the browse plants has been utilized. All browse plants have major portions broken.

OTHER METHODS

126

E. Other Methods

1. Stem Count This technique is used by very few field offices. It will be moved

to BLM’s Rangeland Inventory and Monitoring Supplemental Studies, Technical

Reference 4400-5.

2. Herbage Capacitance Meter Capacitance meters have been used to determine utilization level by assessing the weight of standing vegetation. Since this

procedure is not widely used on arid rangelands, it will not be addressed here.

Additional information on using capacitance meters can be obtained in the following

references:

Currie, P.O., M.J. Morris, and D.L. Neal. 1973. Uses and capabilities of electronic

capacitance instruments for estimating standing herbage. Part 2. Sown ranges.

J. BR. Grassl. Soc 28:155-160.

Morris, M.J., K.L. Johnson, and D.L. Neal. 1976. Sampling shrub ranges with

electronic capacitance instruments, J. Range Manage. 29:78-81.

Neal Donald L., and J.L. Neal. 1973. Uses and capabilities of electronic capacitance

instruments for estimating standing herbage. Part 1. History and Development.

J. Br. Grassl Soc. 28:81-89

Neal, Donald L., P.O. Currie and M.J.Morris. 1976. Sampling herbaceous vegetation

with electronic capacitance instruments, J. Range Manage. 29:74-77.
127

GLOSSARY

VI. GLOSSARY OF TERMS

A

actual use: a report of the actual livestock grazing use certified to be accurate by the

permittee or lessee. Actual use may be expressed in terms of animal unit months or

animal months.

allotment: an area of land designated and managed for grazing of livestock. Such an area

may include intermingled private, State, or Federal lands used for grazing in conjunction

with the public lands.

allotment management plan (AMP): a documented program which applies to livestock

grazing on the public lands, prepared by consultating, cooperating, and coordinating

with the permittee(s), lessee(s), or other involved affected interests.

analysis: (1) a detailed examination of anything complex in order to understand its nature

or determine its essential features; or (2) a separating or breaking up of any whole into

its component parts for the purpose of examining their nature, function, relationship,

etc. (A rangeland analysis includes an examination of both biotic (plants, and animals)

and abiotic (soils, topography, etc.) attributes of the rangeland.)

annual plant: a plant that completes its life cycle and dies in 1 year or less.

animal month: a month’s tenure upon the rangeland by one animal. Animal month is not

synonymous with animal unit month.

animal unit: considered to be one mature cow of approximately 1,000 pounds, either dry or

with calf up to 6 months of age, or their equivalent, based on a standardized amount of

forage consumed.

animal unit month (AUM): the amount of dry forage required by one animal unit for one

month based on a forage allowance of 26 pounds per day.

available forage: that portion of the forage production that is accessible for use by a specified

kind or class of grazing animal.

B

biomass: the total amount of living plants and animals above and below ground in an area

at a given time.

browse: (1) the part of shrubs, half shrubs, woody vines, and trees available for animal

consumption; or (2) to search for or consume browse.

browse plant or browse species: a shrub, half shrub, woody vine, or tree capable of producing

shoot, twig, and leaf growth suitable for animal consumption.
GLOSSARY

128

C

canopy cover: the percentage of ground covered by a vertical projection of the outermost

perimeter of the natural spread of foliage of plants. Small openings within the canopy

are included. Canopy cover is synonymous with crown cover.

class of livestock: the age and/or sex groups of a kind of livestock.

community: an assemblage of populations of plants and/or animals in a common spatial

arrangement.

composition: the proportions (percentages) of various plant species in relation to the total

on a given area. It may be expressed in terms of relative cover, relative density, relative

weight, etc.

cool season species: Plants whose major growth occurs during the late fall, winter, and early

spring.

critical area: An area which should be treated with special consideration because of inherent

site factors, size, location, condition, values, or significant potential conflicts among uses.

crown cover: (See canopy cover.)

D

density: numbers of individuals or stems per unit area. (Density does not equate to any

kind of cover measurement.)

E

ecological site: a kind of rangeland with a specific potential natural community and specific

physical site characteristics, differing from other kinds of rangeland in its ability to

produce vegetation and to respond to management. Ecological sites are defined and

described with soil, species composition, and production emphasis. Ecological site is

synonymous with range site and ecological types (FS).

ecological status: the present state of vegetation of an ecological site in relation to the

potential natural community for the site. Ecological status is independent of use. It is

an expression of the relative degree to which the kinds, proportions, and amounts of

plants in a community resemble that of the potential natural community. The four

ecological status classes correspond to 0-25, 26-50, 51-75, or 76-100 percent similarity

to the potential natural community and are called early seral, mid seral, late seral, and

potential natural community, respectively.

estimated use: the use made of forage on an area by wildlife, wild horses, wild burros, and/

or livestock where actual use data are not available. Estimated use may be expressed in

terms of animal unit months or animal months.
129

GLOSSARY

evaluation: (1) an examination and judgment concerning the worth, quality, significance,

amount, degree, or condition of something; or (2) the systematic process for determining

the effectiveness of on-the-ground management actions and assessing progress toward

meeting management objectives.

F

forage: (1) browse and herbage which is available and can provide food for animals or be

harvested for feeding; or (2) to search for or consume forage.

forage production: the weight of forage that is produced within a designated period of time

or on a given area. Production may be expressed as green, air dry, or oven dry weight.

The term may also be modified as to time of production such as annual, current year, or

seasonal forage production.

forb: (1) any herbaceous plant other than those in the Poaceae (true grasses), Cyperaceae

(sedges), and Juncaceae (rushes) families—i.e., any nongrass-like plant having little or no

woody material on it; or (2) a broadleaved flowering plant whose above-ground stem

does not become woody and persistent.

forestland: land on which the vegetation is dominated by trees. Lands are classified forestland if the trees now present will provide 25 percent or greater canopy cover at maturity.

Lands not presently forestland that were originally or could become forested through

natural succession may be classified as potential natural forestland.

frequency: a quantitative expression of the presence or absence of individuals of a species in

a population. It is defined as the percentage of occurrence of a species in a series of

samples of uniform size.

G

goal: the desired state or condition that a resource management policy or program is designed to achieve. A goal is usually not quantifiable and may not have a specific date by

which it is to be completed. Goals are the base from which objectives are developed.

(See objective.)

grass: any plant of the family Gramineae.

grassland: land on which the vegetation is dominated by grasses, grasslike plants, and/or

forbs. Non-forested lands are classified as grassland if herbaceous vegetation provides at

least 80 percent of the canopy cover, excluding trees. Lands not presently grassland that

were originally or could become grassland through natural succession may be classified

as potential natural grassland.

grasslike plant: a plant of the Cyperaceae or Juncaceae families which vegetatively resembles

a true grass of the Gramineae family.

ground cover: The percentage of material, other than bare ground covering the land surface. It may include live and standing dead vegetation, litter cobble, gravel, stones, and

bedrock. Ground cover plus bare ground would total 100 percent.
GLOSSARY

130

H

half shrub: a plant with a woody base whose annually produced stems die each year.

herbaceous: vegetation growth with little or no woody component; nonwoody vegetation

such as graminoids and forbs.

hedging: (1) the appearance of browse plants that have been browsed so as to appear

artificially clipped; or (2) consistent browsing of terminal buds of browse species that

results in excessive lateral branching and a reduction in upward and outward growth.

herbage: the above-ground material of any herbaceous plant (grasses and forbs).

I

interpretation: explaining or telling the meaning of something and presenting it in

understandable terms.

inventory: the systematic acquisition and analysis of information needed to describe, characterize, or quantify resources for land-use planning and management of the public lands.

K

key area: a relatively small portion of a rangeland selected, based on its location, use, or

grazing value, as a monitoring for grazing use. It is assumed that key areas, if properly

selected, will reflect the overall acceptability of current grazing management over the

range.

key species: (1) forage species whose use serves as an indicator to the degree of use of

associated species. (2) those, species which must, because of their importance, be

considered in a management program.

kind of livestock: species of domestic livestock—cattle, sheep, horses, burros, and goats.

M

monitoring: the orderly collection, analysis, and interpretation of resource data to evaluate

progress toward meeting management objectives.

0

objective: planned results to be achieved within a stated time period. Objectives are

subordinate to goals, are narrower and shorter in range, and have increased possibility of

attainment. Time periods for completion and the outputs or achievements that are

measurable and quantifiable, are specified. (See goal.)

overstory: The upper canopy or canopies of plants, usually referring to trees, shrubs, and vines.
131

GLOSSARY

P

pasture: grazing area enclosed and separated from other areas by fence or natural barrier.

plant association: a kind of potential natural community consisting of stands with essentially

the same dominant species in corresponding layers.

potential natural community (PNC): the biotic community that would become established

if all successional sequences were completed without interferences by human beings

under the present environmental conditions. Natural disturbances are inherent in

development. PNC can include naturalized non-native species.

proper use: (1) a degree of utilization of current year’s growth which, if continued, will

achieve management objectives and maintain or improve the long-term productivity of

the site; or (2) the percentage a plant is utilized when the rangeland as a whole is properly

utilized. Proper use varies with time and systems of grazing. Proper use is synonymous

with proper utilization.

proper utilization: (See proper use.)

public lands: any land and interest in land outside of Alaska owned by the United States

and administered by the Secretary of the Interior through the Bureau of Land Management

(See 43 CFR 4100.0-5.)

R

rangeland: a kind of land on which the native vegetation is predominantly grasses, grass-like

plants, forbs, or shrubs; includes lands revegetated naturally or artificially when routine

management of that vegetation is through manipulation of grazing. Rangelands include

natural grasslands, savannas, shrublands, most deserts, tundra, alpine communities,

coastal marshes, and wet meadows. Rangelands also include lands revegetated naturally

or artificially to provide a plant cover that is managed like native vegetation.

range site: (See ecological site.)

riparian zone: the banks and adjacent areas of water bodies, water courses, seeps, and

springs whose waters provide soil moisture sufficiently in excess of that otherwise

available locally so as to provide a more moist habitat than that of contiguous flood

plains and uplands.

S

savanna: a grassland with scattered trees, whether as individuals or clumps; often a transitional

type between true grassland and forest.

seral community: one of a series of biotic communities that follow one another in time on

any given area. Seral community is synonymous with successional community.

seral stage: the developmental stages of an ecological succession. Seral stage is synonymous

with successional stage.
GLOSSARY

132

shrub: a plant that has persistent woody stems and a relatively low growth habit, and that

generally produces several basal shoots instead of a single bole. It differs from a tree by

its low stature—less than 5 meters (16 feet)—and nonarborescent form.

shrubland: land on which the vegetation is dominated by shrubs. Nonforested lands are

classified as shrubland if shrubs provide more than 20 percent of the canopy cover,

excluding trees. Lands not presently shrubland that were originally or could become

shrubland through natural succession may be classified as potential natural shrubland.

stratification: subdividing an area into units which are, more or less, internally homogeneous

with respect to those characteristics of interest.

stubble: The basal portion of herbaceous plants remaining after the top portion has been

harvested either artificially or by grazing animals.

succession: the orderly process of community change; it is the sequence of communities

which replace one another in a given area.

successional community: (See seral community.)

successional stage: (See seral stage.)

T

tree: a woody perennial, usually single-stemmed plant that has a definite crown shape and

characteristically reaches a mature height of at least 5 meters (16 feet). Some plants,

such as oaks (Quercus spp.), may grow as either trees or shrubs.

trend: the direction of change in ecological status or in resource value ratings observed over

time. Trend in ecological status is described as “toward” or “away from” the potential

natural community or as “not apparent.” Appropriate terms are used to describe trends

in resource value ratings. Trends in resource value ratings for several uses on the same

site at a given time may be in different directions, and there is no necessary correlation

between trends in resource value ratings and the trend in ecological status.

U

understory: plants growing beneath the canopy of other plants. Usually refers to grasses,

forbs, and low shrubs under a tree or shrub canopy.

unsuitable rangeland: rangeland which has no potential value for, or which should not be

used for, a specific use because of permanent physical or biological restrictions. When

unsuitable rangeland is identified, the identification must specify what use or uses are

unsuitable (e.g., “unsuitable for cattle grazing”).

use: (See utilization.)

useable forage: that portion of the forage that can be grazed without damage to the basic

resources; may vary with season of use, species, and associated species.
133

GLOSSARY

utilization: the proportion or degree of the current year’s forage production that is consumed

or destroyed by animals (including insects). The term may refer either to a single plant

species, a group of species, or to the vegetation community as a whole. Utilization is

synonymous with use.

V

vegetation: plants in general, or the sum total of the plant life above and below ground in

an area.

vegetation type: a kind of existing plant community with distinguishable characteristics

described in terms of the present vegetation that dominates the aspect or physiognomy

of the area.

vigor: relates to the relative robustness of a plant in comparison to other individuals of the

same species. It is reflected primarily by the size of a plant and its parts in relation to its

age and the environment in which it is growing.

W

warm season species: plants whose major growth occurs during the spring, summer, or fall

and that are usually dormant in winter.

wet meadow: a meadow where the surface remains wet or moist throughout the summer,

usually characterized by sedges and rushes.
GLOSSARY

134
135

REFERENCES

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Ferguson, Robert B. and Michael A. Marsden. 1977. Estimating overwinter bitterbrush

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J. Range Manage. 18:33-34.

Gierisch, Ralph K. 1967. An adaptation of the grazed plant method for estimating utilization

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Grieg-Smith, P. 1983. Quantitative plant ecology. 3rd Ed. University of California Press

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Hansen, Herbert C. 1962. Dictionary of ecology. Bonanza Books, Crown Publishers, Inc.,

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Harniss, Roy 0. and Robert B. Murray. 1976. Reducing bias in dry leaf weight estimates of

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Hart, R.H. 1980. Determining a proper stocking rate for a grazing system. In: Proceedings,

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Heady, Harold F. 1949. Methods of determining utilization of range forage. J. Range

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———. 1950. Studies on bluebunch wheatgrass in Montana and height-weight relationships

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Watts. 1974. Rangeland entomology. Society for Range Management, Range Science

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Hooper, Jack F. and Harold F. Heady. 1970. An economic analysis of optimum rates of

grazing in the California annual-type grassland. J. Range Manage. 23:307-311.
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Hurd, Richard M. and N.A. Kissinger. 1953. Estimating utilization of Idaho fescue

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Ser., Rocky Mtn. For. and Range Exp. Sta., Ft. Collins, CO, Research Paper. 12.

Hurd, Richard. 1959. Factors influencing herbage weight of Idaho fescue plants. J. Range

Manage. 12:61-63.

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Jensen, Charles H. and George W. Scotter. 1977. A comparison of twiglength and browsedtwig methods of determining browse utilization. J. Range Manage. 30:64-67.

Jones, M.B. and R.A. Evans. 1959. Modification of the step-point method for evaluating

species yield changes in fertilizer trials on annual grasslands. Agron. J. 51:467-470.

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Krebs, C.J. 1989. Ecological methodology. Harper & Row, New York, NY.

Lillesand, Thomas M. and Ralph Kiefer. 1979. Remote sensing and image interpretation.

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Lommasson, T. and Chandler Jensen. 1938. Grass volume tables for determining range

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———. 1943. Determining utilization of range grasses from height-weight tables. J.

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McDougald, Neil K. and Richard C. Platt. 1976. A method of determining utilization for

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McQuisten, Richard and Karl A. Gebhardt. 1983. Analytical reliability in the decision

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137

REFERENCES

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140
141

APPENDIX A

APPENDIX A

Study Location and Documentation Data Form
APPENDIX A

142

Location

Elevation Slope Exposure Aerial Photo Reference

Date Established Established by (Name) Map Reference

Ecological Site Plant Community

District Resource Area

Allotment Name & Number Pasture

Study Method Study Number

Study Location & Documentation Data

Page of

Township 1/4 Range Section 1/4 1/4

Scale: ____ inches

equals one mile

Key Species

Distance and bearing between location stake and bearing stake

Transect Bearing Vertical Distance Between Ground & Aligned Tape

Length of Transect Plot/Frame Size

Sampling Interval Total Number of Samples

Notes (Description of study location, diagram of transect/plot layout, description of photo points, etc. If more

space is needed, use reverse side or another page.)

Distance and bearing between reference post or reference point and the transect

location stake, beginning of transect, or plot

12 3

Note: Depending on the study method, fill in the blocks that apply when a study is established. This

documentation enables the examiners to conduct follow-up studies in a consistant manner to provide

comparable data for analysis, interpretation, and evaluation.

APPENDIX A

144
145

APPENDIX B

APPENDIX B—STUDY IDENTIFICATION

A. Numbering Studies Studies should be numbered to assure positive identification. These numbers can also be used to identify photographs. Following are three

alternative schemes for numbering studies:

1. Numbering Scheme 1. Consecutive numbers may be assigned to studies within

an allotment. For example, Mooncreek #1 and Mooncreek #2 would be studies

Number 1 and 2 within the Mooncreek Allotment. A disadvantage to using the names

of allotments in a numbering scheme is that these names can, and often do, change.

2. Numbering Scheme 2. Studies may be numbered based on their location

within a township, range, and section. A 10-character number can be assigned in

the following manner:

a The first three characters are the township (03S), the second three are the range

(27W), the next two are the section (08), and the last two are simply a series number

(01) assigned to a study based on the number of studies located within a section.

b The numbers for studies located in Section 8 would be 03S-27W-08-01, 03S27W-08-02, and so forth.

c Depending on the local situation, this scheme can be modified by adding characters

to the code where there are fractional townships or ranges, where there are more

than 99 sections/tracts within a township, and/or where there is more than one

public land survey principal meridian and baseline within the area of jurisdiction.

3. Numbering Scheme 3. Studies may be numbered based on their location

relative to the initial point of survey (principal meridian and baseline governing

public land survey).

a Under this scheme, the first character is a letter assigned to a principal meridian

and baseline quadrant. Using the initial point of the survey as the center point,

the northeast quadrant (townships located to the north and east of the initial

point) is coded “A”. The northwest, southwest, and southeast quadrants are

coded “B”, “C”, and “D”, respectively. For example:

A

Salt Lake Meridian

(initial point)

B

C D
APPENDIX B

146

b The next characters are the township number (3, 16, etc.) followed by the

range number (7, 32, etc.) and the section number (8, 21, etc.).

c The next three characters are used to identify the subdivisions within a section

(down to 10 acres) in which a study is located. These subdivisions have letter

designations as follows:

d The last character(s) is (are) simply a series number (1, 2, 3, . . . 10, 11, etc.)

assigned to a study based on the number of studies located within the smallest

subdivision.

e For example, Studies 1 and 2 located in the SE1/4NE1/4NW1/4 of Section 8,

T3S, R21E would be numbered (D-3-21)8Bad-1 and (D-3-21)8Bad-2.

f Depending on the local situation, this scheme can be modified by adding

characters to the code where there are fractional townships or ranges, where

there are more than 99 sections/tracts within a township, and/or where there is

more than one public land survey principal meridian and baseline within the

area of jurisdiction.

C D

A

a

d

b

c

a

c d

a

B

8
147

APPENDIX C

APPENDIX C

Transect Schematic
APPENDIX C

148

180-Degree

Selection Zone

Imaginary Line

Sample Course

Technique for Selecting the Nearest Plant

Transect Schematic

5 ft

5 ft

1

2

3

4

5

6

Permanent Steel Posts
149

APPENDIX D

APPENDIX D

Degrees of Hedging
APPENDIX D

150

A = Zero to Light B = Moderate C = Severe

A C

B

Degrees of Hedging
151

APPENDIX E

APPENDIX E

Utilization Cages
APPENDIX E

152

Folding cages are adaptable to plots of different sizes. The basic construction

employs panels of welded wire, hinged together by No. 9 wire threaded through

a series of wire loops at the edges of each panel. The 4-sided cage constitutes

the basic design, but the number of panels can be increased to enclose larger areas.

A 4-panel cage that is 5 feet square accommodates a 9.6 sq. ft. plot, 5 panels 

accommodate a plot twice that size, and 8 panels accommodate a 96 or 100 sq. ft. 

plot. Procedures for cutting panels from different types of welded wire are shown on

the following page. Cages with an even number of panels will fold flat if the panels are

of equal size. If an odd number of panels are used, one hinge wire must be removed to

permit the cages to fold flat.

Following are some examples of kinds of cages that can be constructed and used

for utilization and production studies. There are many other kinds of cages that

will do the job just as well. No specific cage is recommended.

Below are diagrams of four cage structures produced by varying the number of panels.

For these cages, the basic panel would be of welded 4 by 4-inch wire mesh cut to the

following dimensions: base, 5 feet; height, 5 feet; top, 32 inches. Areas enclosed by

circles within each diagram (left to right) correspond to plots of 4.8, 9.6, 19.2, and 96 

square feet, respectively.

Cage Type 1

Slope of cage sides
153

APPENDIX E

A rigid steel post cage can be constructed by driving four steel posts in the ground

to mark off the area to be protected. Make the posts sturdy by bracing from one post

to another around the perimeter of the cage. Encircle this frame with either net or

barbed wire. These cages are very stable, but they are difficult to move.

The above are diagrams for cutting 5- by 5-foot panels from three types of welded

wire. Loops are formed from horizontal wires as shown—other wires between panels

are cut off.

90° cut

2" x 4" mesh,

11/11 gage,

galvanized

A

40"

Cage Type 2

Cage Type 1 (continued)

76° cut

2" x 4" mesh,

11/11 gage,

galvanized

B

76° cut

4" x 4" mesh,

10/10 gage,

galvanized

C

71.5° cut

4" x 4" mesh,

10/10 gage,

galvanized

D

63.3° cut

6" x 6" mesh,

9/9 gage,

galvanized

E
APPENDIX E

154

Igloo-shaped wire cages are light in weight, low in cost, portable, and easily placed.

The cages are made in sets of four and can be nested. Use 6-inch mesh, 39 inches

high. Wire lighter than 11-1/2 gage is unsuitable. To make four nesting cages: lengths

of field fence are cut with 23, 24, 25, and 26 meshes intact. Each length is formed

into a cylindrical shape and fastened by using the cut ends as ties, except those of

the three upper meshes. The horizontal wires of the three upper meshes are cut at

intervals of 90 degrees so that four nearly equal flaps are formed. These are bent

inward and wired by their cut ends to make the top and complete the cage. A fencing

tool and 8-inch lineman's pliers are suitable tools. In use, four 18-inch stakes of 1/2-inch

reinforcing iron are driven diagonally inward over the bottom wire so that the cage is

held taut and close to the ground. Small mesh wire 1 foot high around the bottom of the

cage will exclude rabbits.

Cage Type 3

fold top in

cut top 3 meshes for fold

total height 39"
155

APPENDIX E

These cages are 4 feet square and are constructed of No. 9 galvanized wire.

Every intersection is electronically welded. Cages are held in place with four

pointed steel stakes, one on each side. These cages are easily transported from

place to place and fold completely flat.

Steel stakes 2'-6" long

Drive in ground 6"

Cage Type 4

2'-0"

4'-0"

4'-0"

6"

2"
APPENDIX E

156

These cages are 4 feet by 5 feet at their base. They are constructed with

40 feet of 1/2-inch iron rod and 20 feet of 39-inch galvanized mesh wire. The size

of the mesh is discretionary. The joints of the rod frame are welded and the wire

is tied to the frame. The cages are held in place with four stakes that are at least

1 foot long, with hooks on the top. These cages are sturdy and are stackable for

storage and transporting.

Cage Type 5

5 ft.

3 ft.

5 ft.

3 ft.

2 ft. 4 ft.

34

inches

3 ft.

Top View

Side View

4 ft.

2 ft.

3 ft.

End View
157

APPENDIX E

These cages are about 4 feet square. They are constructed of prewelded mesh

panels made with 1/4-inch rod. The sides of the cages are made by cutting a

32-inch x 16-foot mesh panel (hog panel) into four equal parts. The top is onefourth of a 52-inch x 16-foot mesh panel. An acetylene torch can be used to cut

the panels to the desired length. The cut ends are bent into different

hooks that hold the cages together. Three types of panels are used for the

sides of the cages and one for the top. This type of cage can be assembled in

less than 5 minutes. The corners all lock together and do not have to be

wired. Steel posts should be put on two sides of each cage to prevent livestock from pushing it around. Construction is strong enough to withstand

cattle rubbing.

Cage Type 6

Panel type 1 (32 inches x about 4 feet).

One of these panels is needed for each cage. Note the hook design

on both ends of this panel (corner hooks on the left and closing

hooks on the right).

Figure 1
APPENDIX E

158

Panel type 2 (32 inches x about 4 feet).

Two of these panels are needed for each cage. Note the hook design (corner

hooks) on the left end of the panel.

Figure 2

Panel type 3 (32 inches x about 4 feet).

This is the closing panel. One of these panels is needed for each cage.

Note the hook design (closing hooks) on the left end of this panel. The

right angle hooks on this panel and those shown on the panel in Picture 1

overlap to form a channel for a rebar rod to be thrust through to close

the cage as shown in Picture 7.

Figure 3
159

APPENDIX E

Top panel (about 4 feet square). One of these panels is needed

for each cage. Note the hook design along two sides of this panel.

Figure 4

Shows how two panels are locked together

using the corner hooks. Three corners of the

cage will look like this. Note that the hooks

are on the outside of the cage.

Figure 5
APPENDIX E

160

Shows three panels (panel type 1 on the

left, panel type 2 in the center and on the

right) locked together. The cage is ready to

have the closing panel (panel type 3) put in

place.

Figure 6

Shows how the closing panel (panel type 3)

is locked to panel type 1 with a rebar rod

being thrust through the closing hooks.

The rod can be long enough to extend

into the ground if desired.

Figure 7
161

APPENDIX E

Completely assembled cage. The top panel is hooked on one side of the cage, laid

across the cage, and held in place with two 1/4-inch locking rods pushed through

loops along the top of the side panels of the cage.

Figure 8
APPENDIX E

162
163

APPENDIX F

APPENDIX F—

SELECTING RANDOM SAMPLES

Selecting random points along a baseline from which to run transects:

1. Select Direction If the baseline bisects the middle of the sample area, the first

determination for selecting the location of a transect is to determine the direction

each transect will be run perpendicular to the baseline. A simple flip of a coin

could be used. Another way of selecting directions is to arbitrarily decide that odd

numbers represent transects to the right of the baseline and even numbers represent transects to the left of the baseline. If five transects are required along a 100-

meter baseline, start at some arbitrary point anywhere on the random digit table

below and select the first five single digit numbers from left to right. As an example, the process could begin with the number sequence in row 15, column 4

(22695). Transects 1, 2, and 3 would be run to the left (numbers 2, 2, and 6), and

transects 4 and 5 would be run to the right (9 and 5).

2. Select Location To select the location of each transect along the baseline, again

start at some arbitrary point on the table of random numbers. In this case, use

two-digit sequences. If row 19, column 3, is selected as the starting point, the five

two-digit sequences would be 33, 52, 15, 56, and 37. Transects would be run at

the 15-, 33-, 37-, 52-, and 56- meter marks along the baseline. Care should be

taken to ensure that adjoining transect do not overlap. Depending on the ecological site and vegetation community, any interval can be selected as the minimum

distance between transects. In this case, 10 meters has been established as the

distance between transects. In the above example, the second and third transects

(at the 33- and 37- meter marks) are within 10 meters of each other on the same

side of the baseline. If they were to be run in opposite directions, there would be

no problem. Since they are to be run in the same direction, discard the transect at

the 37-meter mark and select the next two-digit sequence. A transect at the 39-

meter mark (the next two digits in the table) is still within 10 meters of the

previous transect. Continue the process until all transects are separated by 10

meters. With the next two-digit number sequence being 78, transect locations are

now at the 15-, 33-, 52-, 56-, and 78-meter marks. Since the new third and fourth

transects (52 and 56) are in opposite directions, the five transect locations have

been determined.

The table of random numbers could also be used for baselines over 100 meters. If

the baseline is 200 meters, use a three-digit sequence to select the location of each

transects. Only those three-digit numbers that fall between 1 and 200 would be

used. This method requires the selection of many numbers because most will not

fall between 1 and 200.

There is a more efficient method of selecting random samples, particularly for

two-, three-, and higher-digit numbers. To use this method, the random numbers

must be treated as decimals. In our set of random digits, we would simply place a

decimal point in front of every group of five digits and treat each group as one

random number. Thus, if we entered the table at row 26, column 7, and read

across, we would have the following six random numbers: 0.32978, 0.59902,
APPENDIX F

164

0.05463, 0.09245, 0.37631, and 0.74016. If we used a random number generator,

it would be even easier since these provide random numbers as decimals falling

between 0 and 1.

The formula for using these decimal random numbers for selecting a sampling unit

or point is:

[u x N] + 1

Where: u = Random number (expressed as decimal)

N = Total population size

[ ] = Used to indicate that only the integer part of the product is used in

the calculation

To illustrate how this formula works, let’s say that our baseline is 200 meters long.

Here we need to select numbers between 0 and 200 as points along a baseline.

Consider these points as a “population” of 200 possible points. Using the first of

the six random numbers we came up with above, 0.32978, we calculate:

[0.32978 x 200] + 1

= [65.956] + 1

= 65 + 1

= 66

Thus, 66 is the first point. Using the second random number we have:

[0.59902 x 200] + 1

= [119.80400] + 1

= 119 + 1

= 120

Now we have the second point, 120. We continue in this manner until we have

the five points we need. Although the formula may look difficult, a hand-held

calculator or computer program with a random number generator makes it easy.

The reason for adding the 1 to the integer of the product of the random number

and N is that only whole numbers will be used. Without adding 1, it would be

impossible to obtain the number 200. Consider the highest possible random

number we could obtain, 0.99999. If we multiply this number by 200, we obtain

199.99800; taking the whole integer of this number yields the number 199.

Adding 1 makes it 200.

As a rule of thumb, you should make sure the random numbers have more digits

on the right side of the decimal point than the number of digits in N. In the

example above, N is 200 and we are using random numbers with five digits to the

right of the decimal point, so we are okay.

Note that this process is much more efficient than the first method because we do

not need to reject any numbers. Given the fact that there is only a 1 in 5 chance

of any three-digit number falling between 1 and 200, we would—on the average—

have to examine 25 three-digit numbers to come up with five points under the

first method. Using the second method, on the other hand, we can use the first

five random numbers from the table to select the same five points.
165

APPENDIX F

Table of Random Digits (Zar 1984)

00-04 05-09 10-14 15-19 20-24 25-29 30-34 35-39 40-44 45-49

00 22808 04391 45529 53968 57136 98228 85485 13801 68194 56382

01 49305 36965 44849 64987 59501 35141 50159 57369 76913 75739

02 81934 19920 73316 69243 69605 17022 53264 83417 55193 92929

03 10840 13508 48120 22467 54505 70536 91206 81038 22418 34800

04 99555 73289 59605 37105 24621 44100 72832 12268 97089 68112

05 32677 45709 62337 35132 45128 96761 08745 53388 98353 46724

06 09401 75407 27704 11569 52842 83543 44750 03177 50511 15301

07 73424 31711 65519 74069 56744 40864 75315 89066 96563 75142

08 37075 81378 59472 71858 86903 66860 03757 32723 54273 45477

09 02060 37158 55244 44812 45369 78939 08048 28036 40946 03898

10 94719 43565 40028 79866 43137 28063 52513 66405 71511 66135

11 70234 48272 59621 88778 16536 36505 41724 24776 63971 01685

12 07972 71752 92745 86465 01845 27416 50519 48458 68460 63113

13 58521 64882 26993 48104 61307 73933 17214 44827 88306 78177

14 32580 45202 21148 09684 39411 04892 02055 75276 51831 85686

15 88796 30829 35009 22695 23694 11220 71006 26720 39476 60538

16 31525 82746 78935 82980 61236 28940 96341 13790 66247 33839

17 02747 35989 70387 89571 34570 17002 79223 96817 31681 15207

18 46651 28987 20525 61347 63981 41085 67412 29053 00724 14841

19 43598 14436 33521 55637 39789 26560 66404 71802 18763 80560

20 30596 92319 11474 64546 60030 73795 60809 24016 29166 36059

21 56198 64370 85771 62633 78240 05766 32419 35769 14057 80674

22 68266 67544 06464 84956 18431 04015 89049 15098 12018 89338

23 31107 28597 65102 75599 17496 87590 68848 33021 69855 54015

24 37555 05069 38680 87274 55152 21792 77219 48732 03377 01160

25 90463 27249 43845 94391 12145 36882 48906 52336 00780 74407

26 99189 88731 93531 52638 54989 04237 32978 59902 05463 09245

27 37631 74016 89072 59598 55356 27346 80856 80875 52850 36548

28 73829 21651 50141 76142 72303 06694 61697 76662 23745 96282

29 15634 89428 47090 12094 42134 62301 87236 90110 53463 46969

30 00571 45172 78532 63863 98597 15742 41967 11821 91389 07476

31 83374 10184 56384 27050 77700 13875 96607 76479 80535 17454

32 78666 85645 13181 08700 08289 62956 54439 39150 95690 18555

33 47890 88197 21358 65254 35917 54035 83028 84636 38186 50581

34 56238 13559 79344 83198 94542 35165 40188 21456 67024 62771

35 35369 32234 38129 59963 99237 72648 66504 99065 61161 16186

36 42934 34578 28968 74028 42164 55647 76805 61023 33099 48293

37 09010 15226 43474 30174 26727 39317 48508 55438 85336 40762

38 83897 90073 72941 85613 85569 24183 08247 15946 02957 68504

39 82206 01230 93252 89045 25141 91943 75531 87420 99012 80751

40 14175 32992 49046 41272 94040 44929 98531 27712 05106 35242

41 58968 88367 70927 74765 18635 85122 27722 95388 61523 91745

42 62601 04595 76926 11007 67631 64641 07994 04639 39314 83126

43 97030 71165 47032 85021 65554 66774 21560 04121 57297 85415

44 89074 31587 21360 41673 71192 85795 82157 52928 62586 02179

45 07806 81312 81215 99858 26762 28993 74951 64680 50934 32011

46 91540 86466 13229 76624 44092 96604 08590 89705 03424 48033

47 99279 27334 33804 77988 93592 90708 56780 70097 39907 51006

48 63224 05074 83941 25034 43516 22840 35230 66048 80754 46302

49 98351 97513 27529 65419 35328 19738 82366 38573 50967 72754
APPENDIX F

166
167

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Utilization Studies and Residual Measurements

Interagency Technical Team

U.S. Department of the Interior

Bureau of Land Management - National Applied Resource Sciences Center

P.O. Box 25047

Denver, CO 80225-0047

BLM/RS/ST-96/004+1730

• Rangeland inventory • Utilization studies

• Rangeland monitoring • Residual measurements

• Rangeland evaluation

Unclassified Unclassified

August 1996 Final

Unclassified UL

This interagency technical reference provides the basis for consistent, uniform, and

standard utilization studies and residual measurements that are economical, repeatable,

statistically reliable, and technically adequate. While not all inclusive, this reference

does include the primary study methods used across the West (twig length measurement,

stubble height, comparative yield, paired plot, ocular estimate, key species, heightweight, etc.).

176, including covers