Ecology and Silviculture of Trembling Aspen

Trembling aspen (Populus tremuloides Michx.) generally grows as clones in which stems, ranging from many thousands to only a few, are interconnected by a common root system. When clones are very large, in one recorded case involving about 47␣ 000 stems joined together over a 43 ha area, aspen becomes a candidate for earth’s most massive and oldest organism. Recent analyses suggest that aspen clones, although not individual stems, may be essentially immortal. Management of aspen requires an understanding of how its clonal nature influences responses to silvicultural steps. For many foresters it is a new experience to work with a species that differs from conifers in several important aspects. For example, aspen regulates its density without silvicultural intervention; if silviculturally thinned, aspen may respond by increased sucker production, which can hamper the intended concentration of increment in residual crop trees. A remarkable feature of clonally regenerated aspen suckers is that, after disturbance by fire or clear-cutting, a typical sequence is an early postdisturbance density of 200␣ 000 or more root suckers per hectare, which self-thin to less than 25 ␣ 000 stems per hectare by age 6 and to less than 10␣ 000 by age 10. The initial high stem densities and subsequent rapid natural thinning are relevant for the definition of stocking standards for aspen. This article outlines key autecological features of aspen in terms of environmental tolerances, growth and site factors, regeneration requirements, and stand dynamics. The focus is on post1991 information, which updates other recent reviews on ecology and management of aspen. The need for management innovation is apparent now that technological progress has provided the opportunity to use aspen commercially. In mixed stands over sixty years old the natural elimination of aspen becomes rapid—in the not distant future the aspen in mixed stands of this age will furnish an appreciable amount of pulpwood that will be used, thus avoiding the present total loss of this species. E.H. Garman, 1929 Forestry Chronicle 5(3):28-44.