Survey of Aspen Stands 

 Treated with Herbicides in the 

 Western United States 



Roy 0. Harniss 

 Dale L. Bartos 



INTRODUCTION 



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). Herbi- 

 cide 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 immedi- 

 ately after spraying, and grass production increased 

 approximately 10 times, in part because of aerial seed- 

 ing. However, other problems arose such as mass slump- 

 ing, 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 



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