United States

Department

of Agriculture

Forest Service

Intermountain

Research Station

General Technical

Report INT-GTR-308

June 1994

A Photographic Utilization

Guide for Key Riparian

Graminoids

John W. Kinney

Warren P. Clary
Intermountain Research Station

324 25th Street

Ogden, UT 84401

The Authors

John W. Kinney is Range Technician with the Intermountain Research Station’s Riparian-Stream Ecology

and Management Research Work Unit at Boise, ID.

He received a B.S. degree in botany from Weber State

College. He joined the Forest Service in 1975 and was

stationed at the Desert Experimental Range in Utah for

9 years. He joined the riparian-stream unit in 1984.

Warren P. Clary is Project Leader of the Intermountain

Research Station’s Riparian-Stream Ecology and Management Research Work Unit at Boise, ID. He received

a B.S. degree in agriculture from the University of

Nebraska, an M.S. degree in range management, and

a Ph.D. degree in botany (plant ecology) from Colorado

State University. He joined the Forest Service in 1960

and conducted research on rangelands in Arizona,

Louisiana, and Utah. Most recently he has focused on

riparian-livestock grazing issues in Idaho, Oregon, and

Nevada.

Acknowledgments

We gratefully acknowledge the assistance of Leroy

Alonzo, Fred Galan, Mering Hurd, and Lynda Smithman.

Suggestions by Warren Ririe and Alma Winward at the

initiation of this effort are greatly appeciated. The cover

illustration was drawn by Lenora Oosterhuis, an emigrant from Holland, who is a botanist and a freelance

biological artist living in Boise, ID.
1

Introduction

Determining proper utilization of forage is one of

the most important activities in range management.

Consequently, range technicians have spent a lot of

time studying forage utilization and ways to measure

utilization (Cook and Stubbendieck 1986; Schmutz

and others 1963). Various methods have been developed. Some are quicker, while others take longer but

are more detailed and accurate. A quick and easy

method to estimate plant utilization is needed because

many range managers must survey large areas. One

such method, the grazed-class method, uses photographic guides (Schmutz and others 1963).

Cattle and most large grazing animals are attracted

to riparian areas (Skovlin 1984) (fig. 1). It is, therefore, particularly important to monitor utilization in

riparian areas. A search of the literature revealed

no photographic guides available to estimate percent

utilization for riparian plant species.

We have developed photographic guides for several

key riparian grass and grasslike species to help determine forage utilization. Data and photographs for

these guides were gathered on the Boise and Sawtooth

National Forests, Boise and Vale Districts of the Bureau of Land Management, and on Idaho State land.

Background

The grazed-class method provides a visual comparison standard, making utilization estimates more consistent and accurate. Estimates of utilization are

based on the growth form of the plant rather than

on its size. Variations in height growth due to site

characteristics, seasonal precipitation, or other factors have minimal effect on utilization estimates

(Schmutz 1971).

Lommasson and Jensen (1938, 1943) found each

plant species had a more or less definite growth form,

even though growing conditions may vary. Various

growth forms have been illustrated by Campbell (1943),

Caird (1945), and McDougald and Platt (1976). For

a given growth form, the relationship between the

percent of a plant’s weight that has been consumed

can be estimated based on the percent of its height

left after grazing. Mitchell and others (1993) found

height-weight relationships of western wheatgrass

were affected somewhat by location, grazing history,

and season. However, most differences were small.

The authors concluded height-weight models allow

managers to assess utilization efficiently.

Development of Photographic

Utilization Guides

Photographic guides should relate the appearance

of a plant after a given portion of its weight has been

removed to the height-weight curve (Schmutz and

others 1963) (fig. 2). The first task is determining

how the weight is vertically distributed for each species (Cook and Stubbendieck 1986). Initially, our approach followed that of Schmutz and others (1963).

However, their procedure was developed primarily

for use on bunchgrasses. In riparian areas the plants

are typically sod formers. We soon found that selection of individual “plants” with flowering heads resulted in a biased sample, since many tillers (shoots)

in dense meadows did not produce a flowering stem.

The procedure was modified to use 10-cm-square sections of sod as the sample unit rather than individual

plants.

A Photographic Utilization Guide

for Key Riparian Graminoids

John W. Kinney

Warren P. Clary

Figure 1—Cattle are attracted to riparian areas.
2

Methods

After plants were fully headed, 25 representative

10- by 10-cm areas of sod (called plants in this discussion) were selected from a typical site or sites.

Any tillers of nontarget species were removed. The

plant’s height was measured and divided into 10 to

20 equal linear sections. The plant was clipped

starting from the top, removing the sections in sequence. Each section was placed into a paper bag,

labeled, and ovendried at 100 °

C for 24 hours. The

sections were weighed to the nearest 0.1 g, and the

percentages of total plant weight were calculated.

The heights of the species studied are illustrated in

table 1.

Plant numbers 1, 5, 10, 15, 20, and 25 were photographed for potential use in illustrating the photographic guide. The sod was clipped to ground level at

each side and in front of the target plant for a distance

of 0.5 m. The plants were photographed using a tripod

with the camera mounted at constant angle, distance

from the plant, and height. A black backdrop was

placed behind the plant (fig. 3). A sequence of photographs was taken beginning at the unclipped stage

and continuing as each linear section was removed.

The weight distribution was determined as described

above.

The cumulative weight for each plant was determined for each clipped section removed, and cumulative weight percentages were calculated. The percent

height remaining was plotted against the percentage

of cumulative weight removed. All clipped plant data

for a given species were plotted on the same chart;

the relationship was described by an ocularly fitted

curve.

From the chart curves, the average remaining

height percentage was determined for each of the

grazed classes—0, 10, 30, 50, 70, and 90 percent.

Photographed plant sequences selected for use in

the photographic guide had average deviations from

the height-weight curve of less than 3 percent. If a

close match was not obtained initially, additional

typical plants were photographed until a close fit

was secured.

Figure 2—The relationship of percent height

remaining and percent weight removed for

grazed plants.

Figure 3—Photographic setup when taking

pictures for the photographic utilization guide.

Table 1—Heights of plant species sampled

Height

Plant species Mean Minimum Maximum

- - - - - - - - - - - -cm - - - - - - - - - - -

Redtop bentgrass

(Agrostis stolonifera) 73 58 84

Bluejoint reedgrass

(Calamagrostis

canadensis) 74 60 90

Water sedge

(Carex aquatilis) 55 35 68

Smallwing sedge

(Carex microptera) 35 30 40

Nebraska sedge

(Carex nebrascensis) 54 47 62

Beaked sedge

(Carex rostrata) 61 48 72

Tufted hairgrass

(Deschampsia

cespitosa) 35 28 44

Baltic rush

(Juncus balticus) 74 51 92

Kentucky bluegrass

(Poa pratensis) 44 23 78

Percent Weight Removed

Percent Height Remaining 100

50

0

0 50 100
3

Field Application

The use of photographic guides is based on the appearance of the residual portion of the grazed plant.

Therefore, to estimate the utilization of an individual

plant, its residual stubble is visually compared to the

photographic guide in the appendix. A number of individual utilization determinations are needed to reliably estimate average utilization in an area. “Substantial” statistical precision from a 50- to 100-plant

sample within a homogeneous sample area has been

reported (Kingery and others 1992; Schmutz 1971).

Further suggestions on procedures for using a photographic guide can be found in Schmutz and others

(1963), Schmutz (1971), and Kingery and others

(1992).

Precise documentation of utilization requires additional effort. No absolute plant heights were included

in the illustrations because height varies within plant

species among sites and years. A plant height standard should be established for each species in a locality. The number of plant measurements necessary to

develop a local standard will vary with the precision

required and the variability of the plant population

being measured. Based on our data, about 25 random

plant height measurements should give mean plant

height estimates within 5 percent of the mean at 95

percent confidence (table 2). After a local mean species

height has been established, it can be used to calculate

the proportion of height remaining on each grazed

sample plant. The proportion of weight removed can

be determined from the graphs in the appendix.

Summary

The photographic utilization guides in the appendix

are the first available for riparian herbaceous forage

species in the Intermountain area. They include: redtop bentgrass (Agrostis stolonifera), water sedge (Carex

aquatilis), smallwing sedge (C. microptera), Nebraska

sedge (C. nebrascensis), beaked sedge (C. rostrata),

bluejoint reedgrass (Calamagrostis canadensis),

tufted hairgrass (Deschampsiacespitosa), Baltic rush

(Juncus balticus), and Kentucky bluegrass (Poa pratensis). The scientific nomenclature follows Cronquist

and others (1977).

Photographic utilization guides can be used effectively with little formal training. Instruction should

include both theory and field practice. Otherwise, inexperienced users may tend to overestimate utilization when grazing is light (Boyd 1987) and underestimate utilization when grazing is heavy (Schmutz 1971).

For more precise documentation of utilization, the

height of local species before grazing can be determined, residual stubble heights can be measured,

and the percent weight removed can be determined

from the graphs in the appendix.

References

Boyd, Carol. 1987. Evaluation of the grazed-class

method for estimating forage utilization on transitory rangelands in northern Idaho. Moscow, ID:

University of Idaho. 137 p. Thesis.

Caird, Ralph W. 1945. Influence of site and grazing

intensity on yields of grass forage in the Texas

Panhandle. Journal of Forestry. 43(1): 45-49.

Campbell, R. S. 1943. Progress in utilization standards

for western ranges. Journal of the Washington Academy of Sciences. 33: 161-169.

Cook, C. Wayne; Stubbendieck, James, eds. 1986.

Range research: basic problems and techniques.

Denver, CO: Society for Range Management. 317 p.

Cronquist, Arthur; Holmgren, Arthur H.; Holmgren,

Noel H.; Reveal, James L.; Holmgren, Patricia K.

1977. Intermountain flora: vascular plants of the

Intermountain West, U.S.A. Vol. 6. New York:

Columbia University Press. 584 p.

Kingery, James L.; Boyd, Carol; Kingery, Peggy E.

1992. The grazed-class method to estimate forage

utilization on transitory forest rangelands. Stn.

Bull. 54. Moscow, ID: University of Idaho, College of

Forestry, Wildlife and Range Sciences, Idaho Forest,

Wildlife and Range Experiment Station. 21 p.

Lommasson, Tom; Jensen, Chandler. 1938. Grass

volume tables for determining range utilization.

Science. 87: 444.

Lommasson, T.; Jensen, Chandler. 1943. Determining utilization of range grasses from height-weight

tables. Journal of Forestry. 41(8): 589-593.

McDougald, Neil K.; Platt, Richard C. 1976. A method

of determining utilization for wet mountain meadows on the Summit Allotment, Sequoia National

Forest, California. Journal of Range Management.

29(6): 497-501.

Mitchell, John E.; Elderkin, Robert; Lewis, James K.

1993. Seasonal height-weight dynamics of western

wheatgrass. Journal of Range Management. 46:

147-151.

Table 2—Average number of plant height measurements

needed to establish local standards1

Sampling error

(percent of Confidence level

maximum height) 0.80 0.85 0.90 0.95 0.99

10 2 3 4 6 10

5 10 13 16 23 40

1 247 312 407 578 998

1

Based on the pooled variance of all species sampled.
4

Schmutz, Ervin M. 1971. Estimation of range use

with grazed-class photo guides. Bull. A-73. Tucson,

AZ: University of Arizona, Cooperative Extension

Service and Agricultural Experiment Station. 16 p.

Schmutz, Ervin M.; Holt, Gary A.; Michaels, Charles C.

1963. Grazed-class method of estimating forage

utilization. Journal of Range Management. 16(2):

54-60.

Skovlin, Jon M. 1984. Impact of grazing on wetlands

and riparian habitat: a review of our knowledge. In:

Developing strategies for rangeland management.

Boulder, CO: Westview Press: 1001-1103.
5

Appendix: Photographic Guides and Height-Weight Curves for Nine

Riparian Species Redtop bentgrass (Agrostis stolonifera L.) 0 10 30 50 70 90 Percent Weight Removed

100

90

80

70

60

50

40

30

20

10

0

0 10 20 30 40 50 60 70 80 90 100

Percent Weight Removed

Percent Height Remaining

Rhizomatous or stoloniferous perennials

4 to 10 dm tall

Flowering period mid-June to early August

Seed set August

Palatability moderate

Streambanks, meadows, and moderately moist sagebrush slopes

Low to middle elevations
6

Bluejoint reedgrass (Calamagrostis canadensis Michx.)

Strongly rhizomatous perennials, culms stout, panicle loosely branched

 and rather open

6 to 12 dm tall

Flowering period July to August

Seed set August

Palatability medium when young; tough and unpalatable when mature

Wet meadows, forest openings, and streambanks

Low to high elevations

100

90

80

70

60

50

40

30

20

10

0

0 10 20 30 40 50 60 70 80 90 100

Percent Weight Removed

Percent Height Remaining

0 10 30 50 70 90

Percent Weight Removed
7

Water sedge (Carex aquatilis Wahlenb.)

Stems borne singly or a few together on well-developed, stout, deep-seated,

 creeping rhizomes

3 to 10 dm tall

Flowering period July to September

Seed set August

Palatability moderate

Common in shallow water or wet soil, and on streambanks

Middle elevations

100

90

80

70

60

50

40

30

20

10

0

0 10 20 30 40 50 60 70 80 90 100

Percent Weight Removed

Percent Height Remaining

0 10 30 50 70 90

Percent Weight Removed
8

Smallwing sedge (Carex microptera Mack.)

Plants densely tufted, without creeping rhizomes, culms numerous

3 to 10 dm tall

Flowering period July to early September

Seed set August

Palatability low to medium

Moderately dry sites, in meadows and along streams

Foothills to moderately high elevations

100

90

80

70

60

50

40

30

20

10

0

0 10 20 30 40 50 60 70 80 90 100

Percent Weight Removed

Percent Height Remaining

0 10 30 50 70 90

Percent Weight Removed
9

Nebraska sedge (Carex nebrascensis Dewey)

Plants coarse, stems stout and sharply triangular, vigorously rhizomatous,

 leaves firm, blue-glaucous

2 to 10 dm tall

Flowering period July to September

Seed set August

Palatability high

Wet meadows and other wet places, often in alkaline areas

Lower to middle elevations

100

90

80

70

60

50

40

30

20

10

0

0 10 20 30 40 50 60 70 80 90 100

Percent Weight Removed

Percent Height Remaining

0 10 30 50 70 90

Percent Weight Removed
10

Beaked sedge (Carex rostrata Stokes)

Stems singly or a few together from stout rhizomes, sometimes forming a

 dense sod

6 to 12 dm tall

Flowering period July to September

Seed set August

Palatability low late in the season

Common in wet meadows and marshes, or in standing or slow-moving water

Middle to high elevations

100

90

80

70

60

50

40

30

20

10

0

0 10 20 30 40 50 60 70 80 90 100

Percent Weight Removed

Percent Height Remaining

0 10 30 50 70 90

Percent Weight Removed
11

Tufted hairgrass (Deschampsia cespitosa L.)

Strongly cespitose, tufted perennials with an open panicle

2 to 8 dm tall

Flowering period July to September

Seed set August to September

Palatability moderate

Streambanks and wet mountain meadows to dry uplands

Middle to high elevations

100

90

80

70

60

50

40

30

20

10

0

0 10 20 30 40 50 60 70 80 90 100

Percent Weight Removed

Percent Height Remaining

0 10 30 50 70 90

Percent Weight Removed
12

Baltic rush (Juncus balticus Willd.)

Stems firm, wiry, and more or less terete (cylindrical); coarse, blackish, creeping

 rhizomes are often sod forming

3 to 9 dm tall

Flowering period May to July

Seed set July

Palatability moderately low

Low, wet, often alkaline areas with variable water tables

Valleys and plains to middle elevations

100

90

80

70

60

50

40

30

20

10

0

0 10 20 30 40 50 60 70 80 90 100

Percent Weight Removed

Percent Height Remaining

0 10 30 50 70 90

Percent Weight Removed
13

Kentucky bluegrass (Poa pratensis L.)

Perennials forming dense sods

3 to 7 dm tall

Flowering period May to August, sometimes September

Seed set August

Palatability high

Moderately moist to dry meadows and open woods

Most elevations

100

90

80

70

60

50

40

30

20

10

0

0 10 20 30 40 50 60 70 80 90 100

Percent Weight Removed

Percent Height Remaining

0 10 30 50 70 90

Percent Weight Removed
Federal Recycling Program Printed on Recycled Paper

Kinney, John W.; Clary, Warren P. 1994. A photographic utilization guide for key riparian

graminoids. Gen. Tech. Rep. INT-GTR-308. Ogden, UT: U.S. Department of Agriculture, Forest Service, Intermountain Research Station. 13 p.

Photographic guides are presented to help estimate grazing utilization of important riparian grasses and grasslike plants. Graphs showing the percent of a plant’s weight that

has been consumed based on the percent of its height left after grazing allow utilization

estimates to be refined further.

Keywords: grazing, grazing effects, grazing intensity, grasses, sedges, rushes

The Intermountain Research Station provides scientific knowledge and technology to improve management, protection, and use of the forests and rangelands

of the Intermountain West. Research is designed to meet the needs of National

Forest managers, Federal and State agencies, industry, academic institutions,

public and private organizations, and individuals. Results of research are made

available through publications, symposia, workshops, training sessions, and personal contacts.

The Intermountain Research Station territory includes Montana, Idaho, Utah,

Nevada, and western Wyoming. Eighty-five percent of the lands in the Station

area, about 231 million acres, are classified as forest or rangeland. They include

grasslands, deserts, shrublands, alpine areas, and forests. They provide fiber for

forest industries, minerals and fossil fuels for energy and industrial development,

water for domestic and industrial consumption, forage for livestock and wildlife,

and recreation opportunities for millions of visitors.

Several Station units conduct research in additional western States, or have

missions that are national or international in scope.

The policy of the United States Department of Agriculture Forest Service prohibits discrimination on the basis of race, color, national origin, age, religion, sex,

or disability, familial status, or political affiliation. Persons believing they have

been discriminated against in any Forest Service related activity should write to:

Chief, Forest Service, USDA, P.O. Box 96090, Washington, DC 20090-6090.

INTERMOUNTAIN

RESEARCH STATION