United States 

Department of 

Agriculture 

Forest Service 

Intermountain 

Research Station 

Ogden, UT 84401 

Research Paper 

INT-340 

April 1985 

Survey. of Aspen 

Stands Treated with 

Herbicides 

in the Western 

United States 

Roy 0. Harniss 

Dale L. Bartos 

This file was created by scanning the printed publication.

Errors identified by the software have been corrected;

however, some errors may remain.
THE AUTHORS RESEARCH SUMMARY 

ROY 0. HARNISS is a range scientist at the Forestry 

Sciences Laboratory, Logan, UT. He has conducted 

ecological research i'(l sagebrush and aspen vegetation. He has a B.S. degree from Washington State 

University, Pullman, and an M.S. degree from Utah 

State University, Logan. 

Aspen stands sprayed with herbicide were compared 

to aspen stands not sprayed in the Western United 

States. The herbicide 2,4-D mixed at about 2 lb/acre 

(2.2 kg/ha) with water or diesel was most commonly 

used. Average number of live aspen trees over 

2 inches (5 em) diameter; stand height, age, and 

diameter; basal area; and disease incidence were 

higher in the unsprayed stands. Average number of 

suckers was generally higher in the sprayed stands. 

The exception to sufficient suckering occurred where 

small isolated aspen clones were heavily grazed. There 

were more grass species and fewer forb species in the 

understory of the sprayed stands. Grass and total 

vegetation production was also hi~her in the sprayed 

stands. Vegetative cover was greater in the sprayed 

stands, but organic matter was deeper on the 

unsprayed plots. 

DALE L. BARTOS is an operations research analyst 

with the Intermountain Station, Ogden, UT. For 13 

years (1972-84) he was a range scientist associated 

with the aspen ecosystem project at Logan, UT. Bartos 

holds B.S. and M.S. degrees from Fort Hays Kansas 

State University, and a Ph.D. degree in range science 

from Colorado State University. His principal research 

interests are systems modeling and ecological 

research. 

PESTICIDE PRECAUTIONARY STATEMENT 

This publication reports research involving pesticides. It 

does not contain recommendations for their use, nor 

does it imply that the uses discussed here have been 

registered. All uses of pesticides must be registered by 

appropriate State and/or Federal agencies before they 

can be recommended. 

CAUTION: Pesticides can be injurious to humans, 

domestic animals, desirable plants, and fish or other 

wildlife-if they are not handled or applied properly. 

Use all pesticides selectively and carefully. Follow 

recommended practices for the disposal of surplus 

pesticides and pesticide containers. 

!141 P~.i'_+'f ~LLOW TH. L.ABaL 

U.S. OIPAIT.IIT Of AIIICULTUII 

The use of trade, firm, or corporation names in this 

publication is for the information and convenience of 

the reader. Such use does not constitute an official 

endorsement or approval by the U.S. Department of 

Agriculture of any product or service to the exclusion 

of others that may be suitable. 
Survey of Aspen Stands 

Treated with Herbicides in the 

Western United States 

INTRODUCTION 

Roy 0. Harniss 

Dale L. Bartos 

Western aspen (Populus tremuloides Michx.) forests 

are valued by resource managers for the multiple-use 

values of water, forage, wildlife habitat, and esthetics 

(DeByle 1981). Aspen stands are being managed by 

cutting and burning to rejuvenate aspen and to get a 

better age distribution of stands (Bartos 1981). Herbicide spraying (fig. 1) is now beginning to be used on 

aspen in areas inaccessible or unsuited for cutting or 

burning. However, little information is available to the 

forest manager in the Western United States on what to 

expect from the use of herbicides or how they could be 

used to rejuvenate mature aspen stands. 

Between 1965 and 1967 in central Utah, 470 acres 

(190 ha) were repeatedly sprayed with 2,4-D and 2,4,5-T 

(a total of six times during the growing season) in an 

attempt to convert the deep-rooted aspen and the 

associated communities to a more shallow-rooted grass 

type to increase water production (Robinson 1971). 

Aspen were virtually eliminated from the site immediately after spraying, and grass production increased 

approximately 10 times, in part because of aerial seeding. However, other problems arose such as mass slumping, accelerated erosion, and damage to big game habitat. 

Robinson (1971) indicated that "massive applications of 

herbicides to aspen and associated plant communities 

are not recommended at present since the full ecological 

impact of such treatment is not known." Several years 

after spraying, suckers 10 ft (3 m) tall were abundant. 

In 1958, personnel at the Bridger-Teton National 

Forest sprayed 9,000 acres (3 645 ha) of sagebrush, 

which included aspen stringers, on the Upper Green 

River in western Wyoming. According to Lester (1972), 

the 2,4-D treatment "eliminated or injured" the aspen 

and some conifers. Bartos and Lester (1984) examined 

these aspen stands 22 years later and found abundant 

aspen trees on the sprayed areas. Forbs were still fewer 

in number of species, and there were no differences in 

grasses when compared to unsprayed aspen. 

We decided to evaluate aspen stands that were 

accidentally or purposefully treated with herbicides by 

comparing the overstory and understory of treated and 

adjacent untreated stands throughout the Intermountain 

and Rocky Mountain area. 

Figure 1.-Herbicide sprayed stand of aspen 

in southeastern Idaho after 1 year. 

METHODS 

National Forest personnel in the Western United 

States identified aspen stands treated with herbicides in 

conjunction with sagebrush, aspen, or conifer-release 

spraying projects. Stands were sampled if sprayed and 

unsprayed comparisons in proximity were about 1 acre 

(0.4 ha) and had information on the spray treatment. 

Spray information consisted of herbicide type, rate, 

carrier (water or diesel fuel), time of year, method of 

application, and treatment success on target species. 

Stands were sampled at two levels of intensity. In 

stands selected for intensive sampling, 33- by 33-ft (10-

by 10-m) plots were placed on the contour of the slope in 

relatively uniform and representative sprayed and 

unsprayed vegetation. Environmental attributes 

recorded were: elevation, aspect, slope percentage, and 

depth of soil organic layer, melanized layer, and parent 

material. Tree data determined by species on the entire 
sample plot consisted of: diameter at breast height 

(d.b.h.) of live and dead trees over 2 inches (5 em) d.b.h.; 

stem count of live and dead reproduction in classes of 

less than 20 inches (0.5. ·m) tall, 20 inches to 6.6 ft 

(0.5 m to 2 m) tali, and greater than 6.6 ft (2 m) tall up 

to 2 inches (5 em) d.b.h., and number of stumps and 

diseased trees (primarily conks). Species numbers, 

composition, and frequency of the understory were determined by 33 nested frequency frames in each sample 

plot (U.S. Department of Agriculture 1983). Vegetation 

litter, rock, and bare ground were estimated from six 

points per frequency frame on the sample plot. Understory biomass was determined by both clipping and 

estimating current year's growth, up to 4.9 ft (1.5 m) 

high, by vegetation categories. Four sets of microplots, 

were distributed randomly on the 1,076 ft2 (100 m2) 

macroplot. Each set consisted of five circular 5.4 ft2 

(0.5 m2) microplots clustered so that the biomass of four 

could be estimated as a percentage of the fifth, which 

was then clipped. The clipped vegetation was dried at 

least 48 hours in an oven at 158 °F (70 °C) and weighed 

for biomass. Percentages of the shrub, grass, and forb 

components were estimated on all five microplots. The 

dry weight biomass by vegetation categories is based on 

20 microplots per stand. Photographs of the overstory 

and understory vegetation were taken on all plots. 

On the plots sampled less intensively, the tree and 

environmental data were determined the same as on the 

more intensively sampled plots. The understory species 

cover was ocularly estimated on the entire 1,096 ft2 

2. EAST MTN 

3. FLAGSTAFF PK 

4. MERKLEY SPRING 

5. COLTON 1 

8. COLTON 2 

7. GOOSEBERRY 

8. CROFT 

9. BEAR CR 

10. SAGE MEADOW 

11. GREEN R 

"12. TONGUE 

13. ARAPAHO CR 

14. ALMONT 

15. VULCAN 

18. POISON GULCH 

17.MANCOS 

(100 m2) plot. The sets of microplots to determine 

understory biomass were estimated by vegetation 

categories. 

More sprayed than unsprayed stands were sampled 

because variation was expected to be greater in the 

sprayed stands. All plots were used in an analysis using 

the one-tailed t-test for independent means. 

RESULTS AND DISCUSSION 

We sampled 17 sprayed areas that met our criteria in 

Idaho, Wyoming, Colorado, and Utah (fig. 2); 34 sprayed 

plots and 22 unsprayed plots for comparison were 

sampled (table 1). Sagebrush was the target species for 

most of the herbicide treatments (table 1). Aspen was 

sprayed for stand regeneration on four areas and for 

conifer release on two areas. The h~rbicide most commonly used was 2,4-D in high volatile butyl ester formulations mixed with water or diesel. The indicated rates of 

2 lb/acre (2.2 kg/ha) are possibly higher than that actually applied in the aspen stands associated with sagebrush because of drift and volatilization. Quality control 

and equipment capabilities would also be factors in nontarget applications. Most of the sagebrush spray 

projects in which aspen was hit used fixed-wing aircraft 

in the late 1950's and early 1960's. The rarity of sprayed 

aspen stands in the 1970's when sagebrush was the 

target species coincides with the use of helicopter and 

low-volatile esters. Volatilization effects on nontarget 

species were reduced markedly when low volatile esters 

replaced the high volatile esters. 

Figure 2. -Locations of herbicide treatments in Western United States. 

2 
Table 1.-Herbicide and plot information for 17 aspen stands sprayed with herbicides in the Western United States 

Herbicide 

Month/year 

Location sprayed Type Rate1 Carrier2 Target3 Application4 Elevation Slope 

kg/ha Lblacre m Ft Perce

1. Mytoge Mountain 6/80 2,4-D 2.2 2 w SB Heli 3 017 9,900 9-11 

2. East Mountain 7/59 2,4-D 2.2 2 D SB FW 3 048 10,000 2-6 

3. Flagstaff Peak 7/68 2,4-D 2.2 2 D SB Heli 2 926 9,600 12-14 

4. Merkley Spring 6/58 2,4-D SB FW 2 621 8,600 2-8 

5. Colton 1 6/64 2,4-D 2.2 2 D A Heli 2 621 8,600 5 

6. Colton 2 6/64 2,4-D 2.2 2 D A FW 2 590 8,500 7-9 

7. Gooseberry /67 2,4-D/2,4,5T 2.2 2 D A Heli 2 621-2 865 8,600-9,400 11-18 

w 8. Croft 6/65 2,4-D 2.2 2 D SB/A Heli 2 286 7,500 12-20 

9. Bear Creek 7/82 2,4-D 2.2 2 w A Heli 2 530 8,300 22-33 

10. Sage Meadow 7/82 2,4-D 2.2 2 w A Heli 2 438 8,000 30-35 

11. Green River /58 2,4-D 2.2 2 D SB FW 2 743 9,000 5-17 

12. Tongue 7/60/82 2,4-D 2.2 2 D SB Heli 2377 7,800 18 

13. Arapaho Creek /62 2,4-D w SB FW 2 621 8,600 27 

14. Almont /68 2,4-D SB FW 2 865 9,400 37 

15. Vulcan /81 2,4-D 2.2 2 w SB FW 2 895 9,500 24-27 

16. Poison Gulch /63 2,4-D/2,4,5T 2.2 2 D SB/A Heli 3 017 9,900 4-21 

17. Mancos 177 2,4-D 2.2 2 CR Heli 2 499 8,200 2-5 

1

Acid equivalent. 2W = water, D = diesel. 388 = sagebrush, A = aspen, CR = conifer release. 4Heli = helicopter, FW = fixed-wing. 5N = north, W = west, S = south, E = east. 
Differences occurred between the sprayed and 

unsprayed stands in the direction to be expected 

(table 2). Average number of live trees over 2 inches 

(5 em) d.b.h., stand height, stand age, stand diameter, 

basal area, and disease· incidence were higher in the 

unsprayed stands. Average number of suckers was 

generally higher in the sprayed stands, especially in the 

over 6.5-ft (2-m) category. The larger variation evident in 

the sprayed data is due partly to the variation in the 

number of years since spraying. The range in the 

number of live trees and stand attributes for the 

unsprayed stands is about the expected range for aspen 

forests in the West (Baker 1925; Mueggler and Campbell 

1982). However, average stand height, diameter, and 

basal area appear low for aspen. Perhaps most of the 

aspen stands associated with sagebrush spraying had 

drier site condition or poorer stand quality. Suckering on 

all sprayed stands was generally sufficient for rejuvenating the stand (fig. 3). The exception to sufficient suckering occurred in areas where the aspen clone was small 

Table 2.-Tree and stand attributes for 34 sprayed and 22 unsprayed aspen stands 

Sprayed 

Variable Units x ± 51 

Trees 

Live >5 em no/0.01 ha2 12.1 ±13.0 

Dead >5 em no/0.01 ha 9.0±9.9 

Stumps no/0.01 ha 14.5 ± 9.5 

Suckers 

Live < 0.5 m no/0.01 ha 32.4 ±59.4 

Dead <0.5 m no/0.01 ha 4.0 ± 14.0 

Live 0.5-2 m no/0.01 ha 54.8 ±99.4 

Dead 0.5-2 m no/0.01 ha 11.0±11.7 

Live > 2 m-5 em d.b.h. no/0.01 ha 39.9±45.1 

Dead >2 m-5 em d.b.h. no/0.01 ha 6.3±9.6 

Stands 

Height m 8.7 ±5.7 

Age years 47.7±39.4 

Average d.b.h. em 7.9±5.6 

Basal area m2/0.01 ha 0.102±0.115 

Disease P/A3 0.029 ± 0.172 

1 Average ± standard deviation. 

2Multiply by 100 for numbers/hectare; 40.47 for numbers/acre. 

3Presence or absence. 

Figure 3.-Abundant regeneration of aspen 

3 years after herbicide spraying. 

4 

Unsprayed Range 

x ± s t Prob Sprayed Unsprayed 

21.0 ± 10.3 0.0046 0-53 9-50 

6.7 ±4.3 .1608 0-42 1-16 

3.1 ±4.2 .0000 0-33 0-14 

16.5 ± 19.0 .1155 0-212 0-80 

1.0 ±2.5 .1632 0-80 0-11 

23.0±28.9 .0753 0-548 0-121 

4.9±8.3 .0200 0-37 0-34 

5.2 ± 12.3 .0005 0-131 0-57 

2.1 ±2.6 .0233 0-42 0-8 

12.6 ± 3.4 .0010 0-20 6-20 

83.7±21.8 .0001 0-129 38-117 

15.0 ±3.3 .0000 0-19.6 8.4-20.8 

0.368 ± 0.161 .0000 0-0.4366 0.1208-0.7399 

0.318 ± 0.477 .0010 0-1 0-1 
Figure 4. -Isolated aspen stand treated with 

herbicide with no regeneration of aspen 

because of heavy grazing by deer and cattle. 

(less than 1 acre [0.4 ha]), isolated, and grazed heavily 

by livestock or big game (fig. 4). 

The understory composition had more grass and fewer 

forbs in the sprayed than in the unsprayed stands 

(table 3). Grass and total vegetation production was 

higher in the sprayed than in the unsprayed stands. 

Shrub numbers were slightly lower in the sprayed 

stands. Vegetation cover was greater on the sprayed 

plots, but the organic matter was deeper on the 

unsprayed plots, possibly due to undisturbed litter from 

aspen and understory categories. These results agree 

with expectations of broadleaf herbicide treatments 

(Anderson 1977). Forbs and shrubs would sharply 

decrease early while the grasses would increase after 

spraying. We found that these effects still show 20 or 

more years after treatment. 

Based on the results of our observations and related 

literature, considerations for the use of herbicides on 

aspen that appear appropriate are: 

1. The purpose for the herbicide treatment should be 

clearly identified. Aspen regeneration requires less herbicide and different timing than conifer site preparation 

and release. 

2. The use of 2,4-D at a rate of 2 lb/acre (2.2 kg/ha) 

acid equivalent, low volatile mixed with a water carrier, 

kills most aspen overstory and initiates aspen regeneration. Lower rates of 1 to 1.5 lb/acre (1.1 to 1.6 kg/ha) 

may be effective in checking the aspen overstory and 

initiating suckering. However, this needs to be tested. 

Dicamba and 2,4-D mixtures have been recommended for 

Populus spp. control (Hamel 1983). These should be used 

mostly for conifer site preparations. Glyphosate 

(Roundup®) is being used experimentally in southern 

Utah in the fall for conifer release in stands with abundant aspen suckers, Ribes spp., or both. 

3. Herbicides are most effective for stimulating aspen 

regeneration and conifer site preparation when applied 

soon after aspen reaches the full leaf stage. For conifer 

release, herbicides should be applied 1 to 3 weeks before 

aspen leaf fall to reduce herbicide damage to the conifer. 

4. Spraying large openings in the aspen canopy 

should be avoided to reduce damage to shrubs and forbs, 

especially where aspen regeneration is the goal. Slight to 

moderate reductions of shrubs and forbs beneath the 

aspen should be expected when spraying aspen. 

Table 3.-Understory vegetation and soil attributes for 34 sprayed and 22 unsprayed aspen stands 

Sprayed Unsprayed Range 

Variable Units x ± s x ± s t Prob Sprayed Unsprayed 

Composition 

Shrub Percent 22.5±17.7 23.1 ± 14.3 0.4419 1.1-73.9 4.5-56.6 

Grass Percent 47.5 ± 21.3 33.9±15.7 .0063 8.8-86.7 5.8-64.3 

Forb Percent 31.8±17.9 43.0 ± 18.0 .0129 2.6-58.3 9.9-76.2 

Weight 

Shrub kg/ha 296.1 ± 303.1 284.0 ± 255.9 .4390 2.5-1,147.9 29.5-956.0 

Grass kg/ha 585.7 ± 471.3 400.8 ± 449.8 .0764 6.4-1 ,845.1 17.5-2,018.8 

Forb kg/ha 410.8 ± 343.8 393.4 ± 217.6 .4167 20.8-1 ,078. 9 70.0-832.5 

Total kg/ha 1,292.9 ± 600.6 1 ,078.3 ± 548.7 .0925 241.9-2,351.2 211.2-2,539.4 

Numbers 

Shrub N/0.01 ha 4.0 ± 1.8 4.9±1.4 .0287 2-9 3-8 

Grass N/0.01 ha 5.7 ±2.0 5.9± 1.8 .4049 3-10 1-8 

Forb N/0.01 ha 11.0±4.6 11.9±4.9 .2354 2-22 4-20 

Total N/0.01 ha 20.6±6.1 22.6 ±5.7 .1111 12-31 12-34 

Cover 

Vegetal Percent 81.0±16.8 73.6 ± 19.1 .0729 43-100 30-98 

Litter Percent 18.2±16.5 24.4 ± 18.3 .1052 0-65 0-70.0 

Rock Percent 0.6 ± 1.6 1.7±3.3 .0713 0-7 0-11.1 

Bare ground Percent 0.4 ±0.9 0.8 ± 1.5 .1558 0-3.6 0-5 

Soils 

Organic em 4.2 ± 1.6 5.8±2.8 .0317 2-8 2-12 

A em 25.1 ± 14.8 23.5 ± 11.8 .3650 3.8-60 3.8-53 

B em 40.1±17.4 32.4 ± 12.8 .1204 15-70 15-59 

5 *U.S. GOVERNMENT PRINTING OFFICE: 1985-0-576-040/10534 
REFERENCES 

Anderson, Wood Powell. Weed science: principles. New 

York: West Publishing Company; 1977. 598 p. 

Baker, Frederick S. Aspen in the Central Rocky 

Mountain Region. Department Bulletin 1291. 

Washington, DC: U.S. Department of Agriculture, 

Forest Service; 1925. 47 p. 

Bartos, Dale L. Changes in aspen and associated species 

resulting from manipulation by burning and cutting. 

In: DeByle, Norbert V., ed. Situation management of 

two intermountain species: aspen and coyotes: part 1, 

aspen: Proceedings of a symposium; 1981 April 23-24; 

Logan, UT. Logan, UT: Utah State University, College 

of Natural Resources; 1981: 77-87. 

Bartos, Dale L.; Lester, James E. Effects of 2,4-D on a 

Populus tremuloides community in the western United 

States 22 years after treatment. Great Basin Naturalist. 44(3): 459-467; 1984. 

DeByle, Norbert V. Aspen and its management: an 

introduction. In: DeByle, Norbert V., ed. Situation 

management of two intermountain species: aspen and 

coyotes: part 1, aspen: Proceedings of a symposium; 

1981 April 23-24; Logan, UT. Logan, UT: Utah State 

University, College of Natural Resources; 1981: 5-14. 

Lester, James E. The effects of livestock grazing on the 

response of high mountain vegetation determined from 

a study of net production and utilization. Laramie, 

WY: University of Wyoming; 1972. 105 p. Ph.D. 

dissertation. 

Hamel, Dennis R. Forest management chemicals. 

Agriculture Handbook 585. Washington, DC: U.S. 

Department of Agriculture, Forest Service; 1983. 

645 p. 

Mueggler, Walter F.; Campbell, Robert B., Jr. Aspen 

community types on the Caribou and Targhee National 

Forests in southeastern Idaho. Research Paper 

INT-294. Ogden, UT: U.S. Department of Agriculture, 

Forest Service, Intermountain Forest and Range 

Experiment Station; 1982. 32 p. 

Robinson, Max E. Sheep Creek water evaluation 

project-a study of vegetative type conversion for 

water yield improvement. 1971. Unpublished report 

supplied to authors by Fishlake National Forest, 

Forest Service, U.S. Department of Agriculture, 

Richfield, UT. 

U.S. Department of Agriculture, Forest Service. Range 

analysis handbook. FSH 2209.21 R-4. Ogden, UT: U.S. 

Department of Agriculture, Forest Service, Intermountain Region; 1983. 

Harniss, Roy 0.; Bartos, Dale L. Survey of aspen stands treated with herbicides 

in the Western United States. Research Paper INT-340. Ogden, UT: U.S. Department of Agriculture, Forest Service, Intermountain Research Station; 

1985. 6 p. 

Aspen stands sprayed with herbicides had higher numbers of aspen suckers 

than adjacent unsprayed stands. Understory production was higher due to more 

grass production in the sprayed stands. While the composition of forb species 

was lower, the number of grass species was higher on sprayed stands than on 

unsprayed stands. Vegetative cover was greater on the sprayed plots, but organic matter was deeper on the unsprayed plots. These results agree with expectations of broadleaf herbicide treatments. 

KEYWORDS: Populus tremuloides, trembling aspen, spraying, understory, 2,4-D, 

management 

6 

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