Early Succession following Clearcutting of Aspen Communities in Northern Utah

Abstract

Changes in aspen reproduction and undergrowth production and composition were recorded over a 3-year period following clearcutting. Aspen suckers increased from 2,300 per hectare prior to cutting to a maximum of 44,000 per hectare the second post-cut year, and dropped to approximately 25,000 per hectare by the third year. Undergrowth production on the cut units increased from 1,013 kg/ha prior to cutting to 3,000 kg/ha after three growing seasons; production on the uncut control areas increased from 1,199 kg/ha to 1,539 kg/ha during this period. The significant increase in undergrowth is attributed to the reduction in competition from the removal of the aspen overstory. Clearcutting appeared to increase the proportion of shrubs in the undergrowth and decrease the proportion of forbs. A similarity index comparing the cut and uncut areas suggested that the greatest change in species composition occurred the first year after cutting, with a gradual return towards the precut conditions. The extensive aspen (Populus tremuloides) forests found at intermediate elevations in the intermountain Rocky Mountain West are highly valued multiple-use lands. They are noted for production of livestock forage, wildlife habitat, and scenic beauty, and they are a potentially valuable source of wood products. Through the process of natural plant succession many of these forests are becoming dominated by conifers, frequently within a single aspen generation. Such conversion concerns resource managers because it is usually accompanied by substantial reductions in forage and wildlife habitat. As a consequence, considerable interest has developed in periodically setting back the process of succession in order to maintain communities that are dominated by aspen. Prescribed burning and clearcutting are the 2 main management alternatives for halting succession to conifers and regenerating the aspen forest. Both of these methods involve drastic disturbance of the plant community. Intelligent use of either requires that we understand not only the effect of such disturbance upon the trees, but upon other components of the community as well. Burning is a viable alternative for rejuvenating an aspen forest where fuel conditions are amenable to fire and where the trees have little or no commercial value. Recently we published descriptions of early succession following prescribed burning of aspen communities (Bartos and Mueggler 1981). Clearcutting may be desirable either where burning is not feasible or where the value of the wood is sufficient to finance the cutting operation. Although the ability of western aspen to reproduce prolifically following clearcutting is well documented (Jones 1975, Schier 1976, Schier and Smith 1979), very little information is available regarding the changes in undergrowth likely to occur when the tree overstory is removed by clearcutting. This report describes aspen reproduction and changes in undergrowth composition and production over a 3-year period following Authors are range scientist and plant ecologist with the Intermountain Forest and Range Experiment Station, USDA Forest Service, located at the Forestry Sciences Laboratory, 860 N. 12 E. Logan, Utah, 84321. The authors wish to thank Dr. William A. Laycock for his help in the initial design of the study and in sampling in 1973. clearcutting aspen communities on the Wasatch National Forest in northern Utah.