United States

Department of 

Agriculture

Forest Service

Pacific Northwest

Research Station

General Technical

Report

PNW-GTR-218

August 1988

Habitat-Effectiveness

Index for Elk on Blue

Mountain Winter Ranges

Jack Ward Thomas, Donavin A. Leckenby, Mark Henjum,

Richard J. Pedersen, and Larry D. Bryant

About This File: 

This file was created by scanning the printed publication. Misscans identified

by the software have been corrected; however, some mistakes may remain.
Resource managers in the United States and Canada must face increasing demands for both

timber and wildlife. Demands for these resources are not necessarily incompatible with each

other. Management objectives can be brought together for both resources to provide a balanced supply of timber and wildlife. Until recently, managers have been hampered by lack of

technique for integrating management of these two resources. The goal of the Habitat Futures

Series is to contribute toward a body of technical methods for integrated forestry in British

Columbia in Canada and Oregon and Washington in the United States. The series also applies

to parts of Alberta in Canada and Alaska, California, Idaho, and Montana in the United States.

Some publications in the Habitat Futures Series provide tools and methods that have been

developed sufficiently for trial-use in integrated management. Other publications describe 

techniques not yet well developed. All series publications, however, provide sufficient detail for

discussion and refinement. Because, like most integrated management techniques, these 

models and methods have usually yet to be well tested, before application they should be 

evaluated, calibrated (based on local conditions), and validated. The degree of testing needed

before application depends on local conditions and the innovation being used. You are encouraged to review, discuss, debate, and--above all--use the information presented in this 

publication and other publications in the Habitat Futures Series.

The Habitat Futures Series has its foundations in the Habitat Futures workshop that was 

conducted to further the practical use and development of new management techniques for

integrating timber and wildlife management and to develop a United States and British Columbia management and research communication network. The workshop--jointly sponsored by 

the USDA Forest Service and the British Columbia Ministry of Forests and Lands, Canada--

was held on October 20-24, 1986, at the Cowichan Lake Research Station on Vancouver

lsland in British Columbia, Canada.

One key to successful forest management is providing the right information for decisionmaking.

Management must know what questions need to asked, and researchers must pursue their

work with the focus required to generate the best solutions for management. Research, development, and application of integrated forestry will be more effective and productive if forums,

such as the Habitat Futures Workshop, are used to bring researchers and managers together

for discussing the experiences, successes, and failures of new management tools to integrate

timber and wildlife.

British Columbia Ministry of Forests and Lands R.M. Ellis

U.S. Department of Agriculture, Forest Service Richard S. Holthausen

JACK WARD THOMAS is a research wildlife biologist and LARRY D. BRYANT is 

a wildlife biologist, U.S. Department of Agriculture, Forest Service, Pacific Northwest

Research Station, Forestry and Range Sciences Laboratory, 1401 Gekeler Lane, 

La Grande, Oregon 97850. DONAVlN A. LECKENBY is a research wildlife biologist

and MARK HENJUM is a wildlife biologist, Oregon Department of Fish and Wildlife,

107 20th Street, La Grande, Oregon 97850. RlCHARD J. PEDERSEN is a wildlife

biologist, LI.S. Department of Agriculture, Forest Service, Pacific Northwest Region,

P.O. Box 3623, Portland, Oregon 97204.

Forward

Authors
Thomas, Jack Ward; Leckenby, Donavin A.; Henjum, Mark; Pedersen, 

Richard J.; Bryant, Larry D. 1988. Habitat-effectiveness index for elk on 

Blue Mountain Winter Ranges. Gen. Tech. Rep. PNW-GTR-218. Portland, OR:

U.S. Department of Agriculture, Forest Service, Pacific Northwest Research

Station. 28 p.

An elk-habitat evaluation procedure for winter ranges in the Blue Mountains of 

eastern Oregon and Washington is described. The index is based on an interaction 

of size and spacing of cover and forage areas, roads open to traffic per unit of area,

cover quality, and quantity and quality of forage.

Keywords: Winter range, wildlife habitat, elk, Oregon (Blue Mountains), Blue

Mountains--Oregon, Washington (Blue Mountains), Blue Mountains--Washington.

Abstract
1 Introduction

1 Habitat Attributes

1 Variable 1. Size and Spacing of Cover and Forage Areas 

5 Variable 2. Density of Roads Traveled by Vehicles 

6 Variable 3. Quantity and Quality of Forage 

6 Factors in Considering Forage Quantity and Quality 

11 Variable 4. Evaluation of Cover Quality

11 Selection of an Analysis Area

12 The Habitat-Effectiveness lndex 

15 Deriving an Estimate of Habitat Effectiveness on an Example Area 

18 Associated Land Management Techniques 

18 Timber-Management Activities on Winter Range 

18 Management Tips for Logging 

19 lmproving Forage Quantity and Quality With Prescribed Burning 

20 Fertilization With Chemicals 

20 Grazing by Domestic Livestock 

22 Forage in Cover Stands 

22 Management Tips on Providing Forage 

22 Road Management on Winter Range 

23 Management Tips for Roads on Winter Range 

23 Summary

23 Literature Cited

Contents
USDA Forest Service land managers in the Blue Mountains of Oregon and Washington have been using a habitat suitability index model for Rocky Mountain elk 

(Cervus elaphus nelsonii) summer ranges (or modifications of that model) developed

by Black and others (1976) and Thomas and others (1979) to evaluate elk habitat

conditions. Those original models stated (Thomas and others 1979, p. 114-115):

...cover requirements...on winter range must be considered more 

carefully than for summer range. Animals distributed over thousands of square kilometers at high elevation in spring, summer, 

and fall are forced by increasing snow depths to travel downslope...through spring-fall ranges and by midwinter are concentrated into smaller, more restricted areas....

Most...winter ranges...are at lower elevations where forested areas 

are interwoven with openings...forest cover may be less than optimum, and existing cover is frequently the key to determining how 

animals will use the area....

...lt is inappropriate to do the same for winter range because the 

consequences of error could be greatly magnified. Each winter 

range is different in its vegetative mosaic and the way it is used 

by the animals. The manager should study winter ranges carefully 

before deciding...to alter cover--particularly thermal cover.

We concur. New research on elk use of habitat on summer and winter ranges has

become available, however (Leckenby 1984). Land-use planning requirements 

indicate that a model of elk winter-range habitat effectiveness is required.

Our purpose is to present a model (our working hypothesis) describing the most

important habitat variables operating on elk winter ranges and their interactions. This

proposed model should be field tested and calibrated as soon as possible.

Thomas and others (1979) thought that, based on elk use related to distances from

cover-forage area edges, size and spacing of cover and forage areas were a key to

elk use of forested habitats. Leckenby (1984) verified this hypothesis and described

use patterns in the Blue Mountains.

Thomas and others (1979, p. 109) said, "Optimum...elk habitat is the amount and

arrangement of cover and forage areas that result in the maximum possible proper

use of the maximum possible area...." Leckenby (1984) showed that elk use of cover

is disproportionately greater in cover areas within 200 yards (185.4 meters) of coverforage area edges and of forage areas within 300 yards (278 meters) of such edges.

1

Introduction

Habitat Attributes

Variable 1. Size and

Spacing of Cover and 

Forage Areas
Thomas and others (1979, p. 104-127) defined two types of cover: thermal and 

hiding. Thermal cover was "any stand of coniferous trees 12 meters (40 ft) or more

tall, with an average canopy closure exceeding 70 percent" (p. 114). Disproportionate

use of such cover by elk was thought to be related to thermoregulation. Whether 

such thermoregulatory activity occurs or is significant has been argued (Geist 1982,

Peek and others 1982). In the context of the model presented here, arguing about

why elk show preference for such stands is pointless. They do exhibit a preference

(Leckenby 1984; see Thomas 1979 for a review). As this habitat model is based on

expressed preferences of elk, we continue to use that criterion as a tested habitat

attribute. We cannot demonstrate that the observed preference is an expression of

need, but we predict energy exchange advantages of such cover to elk (Parker and

Robbins 1984). We consider it prudent to assume that preferred kinds of cover 

provide an advantage to the elk over nonpreferred or less preferred options.

Thomas and others (1979, p. 115) thought all levels of canopy closure provided 

some thermal advantage to elk and defined stands with canopy closures of 40-69 

percent as "marginal thermal cover."

Hiding cover (Thomas and others 1979, p. 109) was defined as "vegetation capable 

of hiding 90 percent of a standing adult...elk from the view of a human at a distance

equal to or less than 61 meters (200 ft)." Subsequent research (Leckenby 1984)

revealed that, where satisfactory or marginal thermal cover was available, elk use of

hiding cover per se was less than availability would indicate. No data were collected

during hunting seasons; use of such cover could have been more extensive then.

Additional data suggest that a better model is attained by dividing cover into two

classes--satisfactory and marginal. To avoid an argument over semantics, the term

"thermal" has been dropped. Cover stands will be evaluated under whichever structural class they fit. Stands that fit neither satisfactory nor marginal cover definitions

are called forage areas.

The definitions for the three classes of habitat then are: (1) Satisfactory cover is a

stand of coniferous trees 40 or more feet (12 or more meters) tall, with an average

canopy closure equal to or more than 70 percent; (2) marginal cover is a stand of

coniferous trees 10 or more feet (3 or more meters) tall, with an average canopy 

closure equal to or more than 40 percent; and (3) forage areas are all areas that do

not meet the definition of satisfactory or marginal cover.

Thus, all stands within the winter-range analysis area can be classified as satisfactory thermal cover, marginal thermal cover, or forage areas by using the chart in 

figure 1. The distribution of elk use related to distance from cover-forage edges 

(table 1) was analyzed (Oregon Department of Fish and Wildlife, unpublished data 

on file, Forestry and Range Sciences Laboratory, La Grande, Oregon). Weighting 

factors were derived from these analyses to be applied to the percentage of an 

analysis area within various distances from such edges (table 1).

2
3

Figure l--A chart for classifying stands within the analysis

area as satisfactory thermal cover, marginal thermal cover, or

forage areas.

Table 1—Derivation of weights for use in determining habitat suitability for 

size and spacing of cover and forage areasa
a Oregon Department of Fish and Wildlife, unpublished data on file, Forestry and Range Sciences

Laboratory, La Grande, Oregon.

b Values derived by dividing the number of plots in a single band by the total plots. c Weights derived by dividing the percentage of elk plots in each band by the highest percentage in any 

single band.

d The >1000-yard cover category is composed of three 100-yard bands; the >1000-yard forage area

category, four 100-yard bands. Bands with similar weights were combined by adding the weights for the

band and dividing by the number of bands.

In theory, all the analysis area lying within 100 yards (92 meters) of a cover-forage

area edge would rate a perfect score of 1.0. Leckenby (1984), however, showed that,

although the vast majority of elk used cover within the first 100 yards (92 meters) 

from cover-forage area edges, cover stands less than 133 yards (123 meters) in total

width were used less frequently than stands at least that wide, and core areas of

stands wider than 200 yards (184 meters) were used progressively less as the distance from edge increased. Therefore, we developed three rules not revealed by the

weighting to apply to the relation between cover-stand widths and elk use: (1) Cover

stands less than 200 yards (184 meters) wide are valuable and therefore receive the

same weight (1.0) as do the first 100-yard (92-meter) bands into cover stands of

greater width; (2) when cover-stand widths are being manipulated, widths maintained

at less than 200 yards (184 meters) will reduce the actual use of those stands, regardless of the numerical score indicated, and (3) cover manipulation designed to

maintain or enhance elk use should provide widths of 200 yards (184 meters) to 400

yards (368 meters) for the majority of cover stands. In other words, stands less than

200 yards (184 meters) wide are valuable and receive a score of one. But reduction 

in a stand width below 200 yards (184 meters) is apt to reduce elk use of such

stands.

4

Table 1—Derivation of weights for use in determining habitat suitability for 

size and spacing of cover and forage areasa (continued)
The procedure described here addresses the same relation of elk use to size and

spacing of cover and forage areas described by Thomas and others (1979), using

cover-forage area ratios. The ratio was "shorthand" for judging habitat effectiveness.

Appropriate sizes of cover and forage areas were assumed to be met, and cover was

assumed appropriately distributed between thermal and hiding cover. In practice,

these assumptions frequently were not met. This made the cover-forage area criteria

difficult to apply in habitat analysis except in a more general sense. According to

Leckenby (1984), the size and spacing criteria described by Thomas and others

(1979) remains valid. The technique described here to consider size and spacing of

cover and forage areas eliminates the necessity for assumptions.

Thomas and others (1979), using data published by Perry and Overly (1977) on elk

use of habitat related to roads in the Blue Mountains, described a procedure to evaluate the impact of roads open to vehicular traffic on habitat effectiveness for elk. 

Lyon (1983) used a similar approach to evaluate the impact of roads on elk use of

habitat. The two efforts yielded markedly similar relations. The relation between miles

of roads open to vehicular traffic per square mile of habitat is shown in figure 2.

5

Variable 2. Density

of Roads Traveled

by Vehicles

Figure 2--The relation of miles of roads open to vehicular traffic per square mile of habitat to habitat effectiveness.
No published information is available on the relation between vehicle trips per unit of

time and the effect on elk use of adjacent habitat. Very rare use of roads seems

unlikely to influence elk use significantly. Any traffic at all is a conservative definition 

of "open to vehicle use." If this definition is not acceptable, the criteria should be 

clearly stated and justified. Because knowledge is lacking about the relation between

elk use of habitat and traffic volume, the conservative definition seems prudent.

This relation is determined considering the quantity and quality of elk forages present

in natural openings (that is, grasslands). The biomass of elk forage in the grasslands

will usually be some larger but predictable multiple of the biomass in forested areas

and on transitional rangelands intermixed with the grasslands. Grassland communities dominated by either ldaho fescue (Festuca idahoensis) or bluebunch wheatgrass

(Agropyron spicatum) or both are used as examples. These common bunchgrass

communities comprise much of the winter ranges in the Northwest (Hall 1973,

Hopkins and Kovalchik 1983, Johnson and Simon 1985). Also, these species constitute common and preferred forage for Rocky Mountain elk (Nelson and Leege 1982).

The Thomas and others (1979) model to evaluate elk habitat effectiveness on 

summer and spring-fall elk ranges did not include forage availability per se. Either 

forage availability was assumed not to be a problem on such ranges or the evaluation of forage-cover area ratios was assumed to encompass availability. We think

specifically including the quantity and quality of known key elk-forage species 

(Nelson and Leege 1982) is appropriate because: (1) Elk are concentrated on winter

ranges, and their ability to shift to other areas is limited; (2) forage of adequate 

quantity and quality is often not available during winter; (3) livestock commonly graze

winter ranges before elk migrate there in the fall, which influences the quantity and

quality of the forage available; and (4) snow cover influences forage availability as

well as the forage requirements of elk.

In developing forage quantity and quality as a habitat attribute, we made these 

observations:

1. A sustainable yield of livestock and big game can be produced from managed

forests and rangelands if positive balance exists between seasonally changing 

plant requirements and animal needs.

2. lnteractions between grazing animals and their forage can be coordinated with 

plant physiology to schedule range management actions, such as grazing 

systems or prescribed burning.

3. Grazing by livestock and other range treatments can be scheduled to enhance 

forage quality and thereby increase nutritious food for wild ungulates (Austin and 

others 1983; Austin and Urness 1983; Gates and Hudson 1981a, 1981b; Gavin 

and others 1984; Hobbs and Swift 1985; Urness and others 1983; Willms and 

others 1980, 1981).

6

Variable 3. Quantity

and Quality of Forage

Factors in Considering

Forage Quantity and 

Quality
4. Dual use of range by livestock and big game is more flexible than the "either-or"

use that most land management planning allocations suggest. The competition

between classes of ungulates-elk and cattle, for example--is not complete.

Competition is reduced by differential consumption of forage species and spatial 

and temporal distribution.

5. Forage quantity alone is not a sufficient index by which to judge habitat effectiveness; the interaction of forage quantity with quality is a more appropriate criterion.

6. The quality of fall forage consumed by elk regulates the amount of fat reserves 

elk can accumulate before winter.

7. Satisfactory cover on winter ranges helps prevent depletion of reserves of body

fat before quality forage is available in the spring.

8. Spring forage is sufficiently nutritious and available to satisfy gestation requirements and build reserves of fat that will be used by elk during spring migration to

summer range (Gates and Hudson 1981b, Holl and others 1979).

9. Habitat effectiveness is correlated with use of habitat by elk, physical condition 

of elk, and herd productivity.

10. Habitat effectiveness is poorly related to, and therefore not a good predictor 

of, densities of big game animals. Numbers of elk are influenced by factors not 

related to habitat effectiveness of a particular winter range. These factors include 

elk killed by hunters, weather conditions, conditions on other seasonal ranges, 

and snow depths.

The influence of forage availability on habitat effectiveness is judged by the interaction of the quantity and quality (Hobbs and Swift 1985) of the aboveground biomass remaining on key forage species as of October 1. The relationships are shown

in figures 3, 4, and 5. In essence, the user of the model estimates the percentage of

herbaceous plant cover that is comprised of decreasers (for example, ldaho fescue

and bluebunch wheatgrass) and, from figure 3, determines the score for forage quantity. The user then estimates the percentage of plant height remaining on either ldaho

fescue or bluebunch wheatgrass on October 1 and, from figure 4, determines the 

percentage of forage weight remaining. The score for the forage quality is next

derived from the relation between weight remaining and habitat effectiveness (fig. 5).

Finally, the scores for quantity and quality of forage are combined in a manner 

consistent with their compensatory interactions to derive the score for forage as

described later.

Hobbs and Swift (1985) observed that only at intermediate or low dietary nutrient 

concentrations were estimates of carrying capacity from available biomass greater

than those derived from the interaction of quantity and quality of forage. Analyses of

ecosystems sustaining herbivores demonstrated that nutritional quality of herbage is

inversely related to its abundance. An earlier model (Hobbs and others 1982) was

used to estimate range carrying-capacity for cattle and beef production and forage

improvements resulting from vegetation treatments in the Blue Mountains (Svejacr

7
8

Figure 3--An estimate of total plant cover from decreaser

species (for example, ldaho fescue and bluebunch wheatgrass) is used to determine the forage-quantity habitat effectiveness (HE) score (adapted from Hopkjns and Kovalchik

1983, Johnson and Simon 1985).
9

Figure 4--An estimate of grass height remaining on October 1

after grazing by livestock is used to estimate the weight of

forage available to elk (data courtesy of F.C. Hall. 1985, personal communication).
Figure 5--An estimate of the weight of forage remaining is 

used to determine the forage-quality habitat effectiveness 

(HE) score (data adapted from Hobbs and others 1982, 

Hobbs and Swift 1985).

We derived weights for the forage from the carrying-capacity relations proposed by

Hobbs and Swift (1985). The Hobbs and others (1982) models resolve a paradox in

evaluating carrying capacities among elk habitats. The models reliably predict the

maximum quality of diets obtainable by a specified number of animals--for example,

the number that is the current management objective for wintering elk on a particular

winter range.

A diverse mosaic of forage conditions is desirable on winter ranges; some areas still

retain most of the potential biomass on October 1, and some have had substantial

portions of biomass removed. Such mosaics can be created by various range treatments, such as regulating livestock grazing and use of prescribed fire. Such diversity allows elk the opportunity to optimize the quality of their diet and to adjust 

quickly to changing weather conditions (Austin and Urness 1983, Gates and Hudson

1981a, Medcraft and Clark 1986). The diversity in the quantity and quality of forage

10
remaining on October 1 between areas allows elk to minimize nutrient debits during

periods of deep snow by using low-quality but high-quantity forage sticking out of the

snow or found on windswept aspects. Forage intake rate is naturally (physiologically)

depressed in winter (Gates and Hudson 1981b, Moen 1973, Robbins 1983, Robinette

and others 1973). An analogy can be used to explain this process. Savings (deposited as body fat in summer and fall) are used to compensate for periods of deficit

spending of energy over winter. The depleted savings are replenished with interest in

spring when green, high quality forage is available to meet current energy expenditures and provide surplus that is stored as fat. At this time of year, forage intake is

naturally increasing.

Habitat effectiveness as influenced by the amount and distribution of cover is accounted for by variable 1 (size and spacing of cover and forage areas). In variable 4,

we consider the influence of the quality of cover. Satisfactory cover and marginal

cover were defined earlier (fig. 1).

Based on observed differences in elk preference (Oregon Department of Fish 

and Wildlife, unpublished data on file at Forestry and Range Sciences Laboratory, 

La Grande, Oregon) for these classes of cover, weights were assigned: satisfactory

thermal cover, 1.000; marginal thermal cover, 0.500.

Each analysis area must be permanently delineated so that both individual and cumulative impacts of management activities can be evaluated on the same area. The

analysis area should be large enough to be meaningful for elk use of a particular 

winter range and, to the extent possible, compatible with other recordkeeping needs

of the manager. The selection criteria are otherwise flexible and left to the manager’s

discretion. Once defined, however, the evaluation area becomes the permanent base

on which elk-habitat effectiveness is determined and management alternatives are

evaluated. Boundaries must not be altered as part of an analysis; such alteration can

cause significant changes in the habitat-effectiveness index. Timber sales, silvicuItural treatment, and impacts of roads are best evaluated on individual treatment

areas-such as a timber sale area. Overall effects of such actions on elk-habitat 

effectiveness (that is, impact on the entire analysis area) must then be evaluated for

the cumulative effects of management actions on elk-habitat management objectives.

lnstallation and evaluation of a series of smaller scale actions that meet management

criteria without accounting for cumulative effects can, and usually will, inadvertently

produce elk-habitat effectiveness levels below those selected as a management goal.

11

Variable 4. Evaluation

of Cover Quality

Selection of an 

Analysis Area
The habitat-effectiveness (HE) index for an elk winter range is computed by the 

following procedure:

HESRFC = (HES × HER × HEF × HEC)

1/N ;

where

HESRFC = habitat-effectiveness index, allowing for the 

interaction of HES, HER, HEF, and HEC, 

HES = habitat-effectiveness index derived from size 

and spacing of cover and forage areas, 

HER = habitat-effectiveness index derived from the 

density of roads open to vehicular traffic, 

HEF = habitat-effectiveness index derived from the 

quantity and quality of forage available to elk, 

HEC = habitat-effectiveness index derived from 

cover quality, 

1/N = Nth root of the product taken to obtain the 

geometric mean, which reflects the compensatory interaction of the N factors in the HE 

model.

The geometric mean, or compensatory function (which assumes interactions among

and between the variables), is used in such multiplicative models so that partial compensation for the interacting variables is accounted for (U.S. Fish and Wildlife Service

1981). Optimum conditions exist only if all HE values are 1.0. If any HE value is zero,

the output of the function is zero. A low value (other than zero) for one variable will 

be partially compensated for by higher values of the other interacting variables.

The index resulting from raising any product derived from (HES × HER × HEF × HEC)

to the power of 1/N (1/4 in this case) can be determined from figure 6. The procedural steps for determining HE values are demonstrated by applying them to a hypothetical analysis area with cover and forage distributed as shown in figure 7.

12

The HabitatEffectiveness Index
13

Figure 6--Conversion for (HES x HER x HEF x HEC) to

(HES x HER x HEF x HEC)1/N.
14

Figure 7--Distribution of cover and forage areas on a

hypothetical analysis area.
Step 1. Computation of HES. Habitat effectiveness for size and spacing (HES) is

derived by examining a map of the analysis area showing the distribution of cover

(satisfactory and marginal thermal cover) and forage areas. Computations are then

made of the amount of area lying within various bands of distance from cover-forage

edges (see table 1). Such an analysis can be made either from standard maps by

manual procedures or from digital data available from LANDSAT satellites. The 

techniques and procedures for obtaining the necessary information from LANDSAT

are automated and available to managers (Isaacson and others 1982; Leckenby

1979, 1984; Leckenby and others 1985; Murray and Leckenby 1985).

The distribution of land area by 100-yard (92-meter) bands from cover-forage area

edges is shown in figure 8. HES is computed by multiplying the weights for each 

distance band from the nearest cover-forage edge (table 1) times the percentage of

the analysis area within each band (fig. 8). These products are then summed to give

the value for HES. This procedure is illustrated in table 2. The resulting HES for this

example is 0.61.

15

Deriving an

Estimate of Habitat

Effectiveness on an

Example Area

Figure 8--Percentage of the analysis area in 100-yard bands

from cover-forage area edges.
When the impact of various vegetative treatments is evaluated, the resulting redistribution of cover and forage areas is mapped, and the new proportion of areas that

fall in the distance bands from the cover-forage area edges is recalculated. The 

resulting HES (after treatment) is then compared with the pretreatment HES or that

from other alternative treatments.

Step 2. Computation of HER. Habitat effectiveness as influenced by roads open to

vehicular traffic is considered next. The miles of roads open to vehicular traffic are

determined for the analysis area. These data are converted to a density figure as 

follows :

Road density = miles of roads open to vehicular traffic/square 

miles in the analysis area.

This example has 50 miles of roads. Thirty miles of those roads are open to vehicular traffic, and the analysis area encompasses 10 square miles. The density of roads

open to vehicular traffic is, then:

Road density = 30/10 = 3 miles/square mile.

Now, refer to figure 2. The HER at a road density of 3 miles/square mile is 0.42.

Step 3. Computation of HEF. Habitat effectiveness resulting from forage quantity 

and quality (HEF) requires on-the-ground inspection.

The procedure to be used is as follows:

1. The percentage of herbaceous cover made up of decreaser species (that is, 

bunchgrasses) and the percentage of height of ldaho fescue and bluebunch 

wheatgrasses remaining on October 1 are determined (figs. 3 and 4). 

16

Table 2—Computation of example HES
2. Bluebunch wheatgrass makes up 50 percent of the herbaceous cover, which 

corresponds to an HEF score of 0.5 (from fig. 3).

3. If 20 percent of the height of bluebunch wheatgrass remains, 34 percent of 

the aboveground biomass is determined to remain (from fig. 4).

4. This weight of biomass of bluebunch wheatgrass remaining (that is, 34 percent) 

is used to determine the forage-quality portion of the HEF score from figure 5

which, in this example, is 1.0.

5. The interaction of the two scores (forage quantity and forage quality) of 0.5 and 

1.0 is computed by the following formula:

HEF = (HEQuan × HEQual)

1/N

= (0.5 × 1.0)1/2

= 0.71.

Step 4. Computation of HEC. Cover is in one of two classes described earlier, 

satisfactory or marginal.

The percentage of cover in each of the two classes is computed next. Multiply the

percentage in each class by the weight applicable to that class (satisfactory, 1.00;

marginal, 0.50). In this case, 60 percent of the cover is satisfactory cover, and 40 

percent is marginal. The HEC index is derived as shown in table 3.

Table 3—Computation of example HEc

17

a Derived by multiplying percentage of the cover in the class by weight for the class and dividing that 

product by 100.

Step 5. Computation of HESRFC. Overall habitat effectiveness (HESRFC) considers

the interaction of: (1) size and spacing of cover and forage areas ( HES), (2) density 

of roads open to vehicular traffic ( HER), (3) forage quantity and quality ( HEF), and 

(4) the quality of cover ( HEC). It is computed as follows:

HESRFC = (HES × HER × HEF × HEC)

1/N

(0.61 × 0.42 × 0.71 × 0.80)1/4

(0.15)1/4

0.62 (as derived from fig. 6).
The HE index describes habitat effectiveness for elk on Blue Mountain winter ranges

by evaluating four variables within a delineated management area (1) size and 

spacing of cover and forage stands, (2) cover quality, (3) roads open to vehicular 

traffic, and (4) quantity and quality of forages. Other activities on winter ranges influence these attributes of elk habitat. Klemmedson (1967) listed the following 

activities and agents as the most important contributors to the downward trend of 

winter ranges: forestry and range management; wildfire; ecological succession; 

overuse by livestock and big game; insects; disease and rodents; roads and highways; recreation; urban expansion; flood and soil erosion; and water development

projects.

We now describe relations of several management techniques to modify the activities

and agents mentioned. Each is examined by how they might be applied to winter

ranges to minimize adverse impacts, to mitigate effects of past management 

activities, or to improve habitat conditions for elk.

Timber-management activities conducted on winter range in winter months can be

particularly disturbing to elk. In a study of habitat use in a logged and unlogged forest

environment on summer range, elk use of newly logged areas during the summer of

logging and the next year was depressed (Pedersen and others 1980). Beall (1976)

suggested that logging activity on a winter range caused initial avoidance by elk that

lasted 2 weeks. After that period, elk resumed normal activities. Areas receiving light

to medium use by elk in the winter before logging received no use by elk the winter

after logging.

Parker and others (1984, p. 486) suggested that "Logging affects energy requirements of elk by influencing snow depth through removal of canopy interception of

falling snow." Essentially, the elk uses more energy moving through deeper snow, 

and less forage is readily available. During a storm, more snow accumulates in 

created openings than in adjacent forested stands because snow interception is

greater in the forested stands. Much of the snow that falls in the open and piles up 

on the surface would never reach the ground in the forest.

• Restrict logging of winter ranges to times when elk are absent (spring, summer, 

and fall).

• If logging is conducted in the winter, concentrate activities into the shortest time

and smallest area possible.

• Provide "security areas," where no management activities are underway adjacent 

to active timber sales. Provide an area at least as large as the sale area, with 

line-of-sight topographic barriers, and closed to vehicular traffic (Lyon 1979, 1980;

Ward and others 1980).

• Do not log adjacent drainages simultaneously (Thomas and others 1979). 

• Plan logging to provide a diversity of cover classes throughout the winter range

area.

18

Associated Land

Management

Techniques

Timber-Management

Activities on Winter

Range

Management Tips

for Logging
Historically, fire was the most important factor affecting plant succession and species

on most lower elevation sites that are now winter ranges (Dell 1980, Gruell 1980,

Houston 1982). Gruell (1980) suggested that a reduction in acres burned has allowed

vegetation to reach advanced succession at the expense of herbaceous plants and

deciduous shrubs and trees. With advancing succession, the carrying capacity for elk

declined.

Results from prescribed fires, designed to improve forage on winter range, are as

diverse as the habitats on which they were conducted. Skovlin and others (1983) 

concluded that fall burning on a foothill rangeland in the northern Blue Mountains did

not increase elk use during winter. Burning was conducted after fall rains had begun;

this may have influenced production of forage on the treatment plots.

In mixed conifer/pinegrass communities studied by Hall (1977), prevention of underburning decreased elk forage (pinegrass [Calamagrostis rubescens] and elk sedge

[Carex geyeri]--the most palatable plants) and increased tree cover. Forage production was only 50 to 100 pounds per acre (56 to 112 kg/ha). In the same community

type where periodic underburning had occurred, tree canopy averaged 50 percent 

and forage production was 500 to 600 pounds per acre (560 to 672 kg/ha). A portion

of the increase in forage production on burned plots may have been attributable to 

the decreased canopy closure of the trees (McConnell and Smith 1970k thus, 

probably not all the additional forage resulted from the effects of fire per se.

Hobbs and Spowart (1984) warned that inferences on the benefits to ungulates from

prescribed fires may severely underestimate the values of burning to the nutrition of

big game if those inferences are based only on changes in forages and not on

changes in diet. They observed that prescribed burning greatly improved the quality 

of winter diets of mountain sheep (Ovis canadensis) and mule deer (Odocoileus

hemionus) in two plant communities but only small changes in quality of individual 

forages were noted. More green grass was observed on burned plots than on unburned plots in the winter, primarily because of removal of standing dead herbage 

and warmer soil temperatures, the latter being enhanced by greater absorption of 

sunlight by blackened soil surfaces.

Ungulates were able to select more weight of highly nutritious green grasses from

burned plots and, consequently, to alter significantly the quality of their diet. Spring

forages on control plots were phenologically younger and therefore higher in quality

than on burn plots because growth had started earlier in the spring on the burned

plots. Differences in initiation of plant growth between burned and control plots 

benefit ungulates by offering two temporally, distinct flushes of nutritious plant tissue,

early on the burn and late on the control. This prolongs the time when nutritious 

forage is available to ungulates.

Such results emphasize the importance of diversity of habitats and treatment conditions in providing forage choices for ungulates under various climatological and snow

conditions.

19

Improving Forage

Quantity and Quality

With Prescribed Burning
Factors that can influence whether a prescribed burn will meet desired objectives for

forage enhancement follow:

1. The heat tolerance of the forage species. The morphology of a plant has a 

direct influence on its tolerance to heat. For example, bunchgrasses in general

have low tolerance to fire because their densely clustered culms can burn for 

several hours. Among the bunchgrasses, wheatgrasses are the most heat tolerant

because their coarse stems burn out quickly.

2. Fire resistance of the forage species. Resistance of a plant to burning is related to carbohydrate reserves. Such reserves are generally lowest during the 

active growing season, and burning during this time can be damaging to some

species.

3. Time of year. Spring burning of ldaho fescue can cause damage or mortality 

to the plant, whereas burning in the fall after the plants have become dormant 

will cause little damage.

Prescribed burning as a technique to improve forage quality for ungulates has had

mixed results. the response of elk to prescribed burning on winter range must be

closely evaluated to assure that specific objectives are achieved.

lnformation on use of fertilizer to improve forage quantity and quality for elk on winter

range is scarce. Skovlin and others (1983) observed that fertilizing winter range in 

the northern Blue Mountains in fall increased elk use in the winter by 49 percent the

first winter after application. No carry-over effects were observed in elk response in

succeeding years. Applying fertilizer was not cost-effective but may be beneficial in

certain situations.

Bayoumi and Smith (1976) reported an increase in forage quantity and quality after

fertilization of a sagebrush-grass-type winter range and suggested that fertilization

may not prove cost-effective in increasing elk use where sufficient forage is available

to meet normal winter requirements.

As with prescribed burning, fertilizing rangelands to improve quantity and quality of

forage has had mixed results. Skovlin and others (1983) recommend that land 

managers contemplating fertilization develop simple field trials on individual winter

ranges to determine feasibility under various range conditions.

Using livestock to improve forage conditions on big game winter range is the subject

of considerable debate. In separate grazing studies conducted on elk winter ranges 

in northeastern Oregon, opposite conclusions about the effects of livestock grazing 

on elk use were presented. Anderson and Scherzinger (1975) thought that light 

grazing by cattle in spring and early summer stimulated regrowth that was higher in

nutrients than ungrazed range. This improved forage was thought to have attracted

additional elk to the study area. Conversely, Skovlin and others (1983) observed that

elk use declined on areas that were grazed in the spring by cattle on winter range

(measured by counts of pellet groups) during the second winter of a 3-year study in

northeastern Oregon.

20

Fertilization With

Chemicals

Grazing by Domestic

Livestock
The disparity between the two studies might be explained by Collins and Urness

(1979), Hobbs and Spowart (1984), and Hobbs and Swift (1985). Collins and Urness

(1979) reported that "distribution of elk pellet groups did not give accurate representation of relative habitat segment use." Elk defecated at a greater rate when active,

such as walking from one area to another. Other work by Collins (1977) indicated 

that elk move about less in more productive habitat-the most preferred for grazing.

Pellet-group counts underestimate elk use in these rich-forage areas because elk 

travel less when feeding there, and they defecate less often when they are less

active.

Hobbs and Spowart (1984) observed that improvement in diet quality for ungulates

after fire was related to green grass on burned plots. Green grass on unburned sites

was obscured by standing dead herbage and litter on the ground. Austin and others

(1983) observed this with mule deer also. Hobbs and Swift (1985) noted that burns

contained more forage with high nutrient concentrations but less forage overall. They

noted that forage quality is inversely related to its abundance in many ecosystems.

These observations can be related to the data collected by Skovlin and others 

(1983). The grazed plots were structurally similar to the burn plots of Hobbs and

Spowart (1984k that is, dead herbage was removed and green forage was more 

available. The elk-use data of Skovlin and others (1983) may have been misinterpreted in light of the work by Collins and Urness (1979); we would expect fewer 

pellet groups on grazed plots because more highly nutritious green forage would be

available to elk. This is further supported by the observation of Skovlin and others

(1983, p. 187) related to the reduction in elk use (pellet counts) during the second

winter, "The winter with the least snow and heaviest elk use." The details of this

observation are not known. If elk concentrations were high and green forage was

more available on grazed plots, we would expect fewer pellet groups on these plots.

Anderson and Scherzinger (1975) developed a livestock grazing system based on 

the morphological and physiological characteristics of forage plants. The objectives

were to remove dead herbage to prevent formation of wolf plants and to improve 

quality of forage regrowth by manipulating the physiology of forage plants through

livestock grazing. This concept has been strengthened through the work of Hobbs 

and Spowart (1984), Hobbs and Swift (1985), and Pitt (1986) and it supports distributions of elk and deer observed on many winter ranges.

In studies of northeastern Oregon rangelands (Miller and Vavra 1981) and elk range 

in Yellowstone (Houston 1982), south exposures and windswept ridges provided a

major portion of winter forage consumed by deer and elk. These areas continued to

be important into early spring because they provided a new source of abundant 

green forage. These areas had the greatest potential for competition for forage

between livestock, elk, and deer.

21
Forage inside cover stands is important to elk in periods of deep snow when forage 

is not available in open areas. Canopy intercept of snow reduces snow depth inside

these stands and makes forage more available (Leckenby 1984, Parker and others

1984). Leckenby (1984) observed abundant lichens (Alectoria sp.) that were much

used by elk inside satisfactory cover stands. Samples of this rich and often overlooked elk food contained 1.99-2.24 M cal of digestible energy per kilogram of dry

matter and 6-7 percent crude protein.

A diversity of crown closures in cover stands and forage areas on winter range will

provide elk with foraging opportunities that can be used in response to varying climatological and snow conditions. This, in turn, seems likely to enhance survival and 

optimize productivity (Beall 1976, Leckenby 1984, Moen 1973, Parker and others

1984, Wickstrom and others 1984).

• A diversity of forage conditions (in terms of forage structure; that is, grazed, 

burned, forage inside cover, ungrazed) will provide an array of grazing opportunities under varying climatological and snow conditions.

• Use of a livestock-grazing system keyed to the physiology and morphology of the

forage species to improve forage quality on winter range can improve the nutritional status of wintering elk.

• Prescribed burning, judiciously applied, holds promise for improvement of forage

quality on winter range if management objectives provide an array of forage 

conditions.

• Use of fertilizers to improve forage quality on winter range is not usually costeffective.

Roads affect elk by removing elk habitat from production of plants and by introducing

a disturbance factor (vehicles), which reduces the use of elk habitat adjacent to 

roads (Compton 1975, Lyon 1979, Marcum 1976, Morgantini and Hudson 1979,

Pedersen and others 1979, Perry and Overly 1977, Rost and Bailey 1974).

Cupal and Ward (1976) concluded that sufficient evidence indicates that direct and

indirect effects of road construction, logging, vehicles, and harassment affect elk 

physiology negatively. These effects were briefly discussed by Ward and others

(1976).

Aune (1981) and Richens and Lavigne (1978) observed that the greatest flight 

distances for elk on winter range were in response to human disturbances, such as

those caused by skiers or hikers. Unanticipated disturbance seemed to be the most

detrimental to wintering animals.

Energy expenditure calculations by Severinghaus and Tullar (1975) demonstrated the

danger of snowmobile harassment to deer in winter. Flight distances caused by 

snowmobiles averaged about 37 yards for elk compared with 59 for skier interactions

in Yellowstone National Park (Aune 1981, Parker and others 1984). 

Parker and others (1984) suggested that the add tional energy drain an wintering wild 

ungulate populations after disturbance by winter recreationists on poor winter ranges

may be an important factor in survival of the population.

22

Forage in Cover

Stands

Management Tips on

Providing Forage

Road Management

on Winter Range
• Restrict human access to winter ranges if the welfare of elk is a primary concern

(Parker and others 1984).

• Elk welfare should be a primary consideration in the design and management of

roads on elk winter ranges (Pedersen and others 1979).

Habitat effectiveness is an index accounting for elk-habitat conditions on winter

ranges in managed forests. The index relates to potential levels of elk use of habitats, elk productivity, and suitability of habitats for elk--that is, it is a biologically 

based index. This index reflects elk-habitat effectiveness during a period of the year

when elk are not hunted. Habitat management to enhance the hunting experience, to

reduce the number of elk killed or the rate of elk killed during hunting season, or to

benefit other wildlife are different issues and not addressed here.

Where the management objective is to give elk some degree of protection from

hunters to enhance the difficulty of hunting or to spread the kill over a longer season

(thereby providing more days of hunting recreation) or both, or to improve the welfare

of animals dependent on old-growth forest stands, increasing the cover component

appreciably would be desirable.

Anderson, E.W.; Scherzinger, R.J. 1975. lmproving quality of winter forage for elk 

by cattle grazing. Journal of Range Management. 28: 120-125.

Aune, K.E. 1981. lmpacts of winter recreationists on wildlife in a portion of Yellowstone National Park, Wyoming. Bozeman, MT: Montana State University. 111 p.

M.S. thesis.

Austin, D.D.; Urness, P.J. 1983. Overwinter forage selection by mule deer on 

seeded big sagebrush-grass range. Journal of Wildlife Management. 47(4): 1203-

1207.

Austin, D.D.; Urness, P.J.; Fierro, L.C. 1983. Spring livestock grazing affects 

crested wheatgrass regrowth and winter use by mule deer. Journal of Range

Management. 36(5): 589-593.

Bayoumi, M.A.; Smith, A.S. 1976. Response of big game winter range vegetation to 

fertilization. Journal of Range Management. 29: 44-48.

Beall, Robert C. 1976. Elk habitat selection in relation to thermal radiation. In: Hieb, 

S.R., ed. Elk-logging-roads: Proceedings of a symposium. Moscow, ID: University

of ldaho: 97-100.

Black, H., Jr.; Scherzinger, R.; Thomas, J.W. 1976. Relationships of Rocky 

Mountain elk and Rocky Mountain mule deer to timber management in the Blue

Mountains of Oregon and Washington. In: Hieb, S.R., ed. Elk-logging-roads:

Proceedings of a symposium. Moscow, ID: University of Idaho: 11-31.

Collins, W.B. 1977. Diet composition and activities of elk on different habitat segments in the lodgepole pine type, Uinta Mountains, Utah. Logan, UT: Utah State

University. 74 p. M.S. thesis.

23

Management Tips

for Roads on Winter

Range

Summary

Literature Cited
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24
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25
Lyon, L.J. 1983. Road density models describing habitat effectiveness for elk. 

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26
Peek, J.M.; Scott, M.D. Nelson; L.J.; Peirce, D.J.; Irwin, L.L. 1982. The role of 

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and snowmobile trails in Maine. Canadian Field-Naturalist. 92: 334-344.

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National Forest. Proceedings, The Wildlife Society Meeting, Northwest Section,

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affected by cattle grazing, fertilizing, and burning in southeastern Washington.

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estimated carrying capacity and potential beef production. Journal of Range

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Urness, P.J.; Austin, D.D.; Fierro, L.C. 1983. Nutritional value of crested wheatgrass for wintering mule deer. Journal of Range Management. 36(2): 225-226.

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construction and use on big game populations. Final Rep. FHWA-rd-76-174.

Springfield, VA: National Technical lnformation Service. 88 p.

27
Ward, A.L.; Fornwalt, N.E.; Henry, S.E.; Hodorff, R.A. 1980. Effects of highway 

operation practices and facilities on elk, mule deer, and pronghorn antelope. Rep.

FHWA--79-143. Washington, DC: Research and Development, Federal Highway

Administration, U.S. Department of Transportation. 48 p.

Wickstrom, M.L.; Robbins, C.T.; Hanley, T.A.; Spalinger, D.E.; Parish, S.M. 1984.

Food intake and foraging energetics of elk and mule deer. Journal of Wildlife

Management. 48(4): 1285-1301.

Willms, W.; Bailey, A.W.; McLean, A.; Tucker, R. 1980. The effects of fall grazing 

and burning bluebunch wheatgrass range on forage selection by deer and cattle in

spring. Canadian Journal of Animal Science. 80: 113-122.

Willms, W.; Bailey, A.W.; McLean, A.; Tucker, R. 1981. The effects of fall 

defoliation on the utilization of bluebunch wheatgrass and its influence on the 

distribution of deer in spring. Journal of Range Management. 34: 16-18.

28 ✩ U.S. GOVERNMENT PRINTING OFFICE:1988 594-696
Thomas, Jack Ward; Leckenby, Donavin A.; Henjum, Mark; Pedersen, 

Richard J.; Bryant, Larry D. 1988. Habitat-effectiveness index for elk on 

Blue Mountain Winter Ranges. Gen. Tech. Rep. PNW-GTR-218. Portland, 

OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest 

Research Station. 28 p.

An elk habitat evaluation procedure for winter ranges in the Blue Mountains of 

eastern Oregon and Washington is described. The index is based on an interaction of size and spacing of cover and forage areas, roads open to traffic per 

unit of area, cover quality, and quantity and quality of forage.

Keywords: Winter range, wildlife habitat, elk, Oregon (Blue Mountains), Blue

Mountains--Oregon, Washington (Blue Mountains), Blue Mountains--Washington.

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