2009-02-26_REPORT - C1994082 (15)

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• from shrubby at upper and lower forest margins to over 30.5 m (100 ft) in height in prime locations with average heights of 15 to 18 m (50 to 60 ft) (Baker 1925). In any case, the initiation of bud growth must also be accompanied by sufficient sunlight and warmer soil temperatures to allow the new suckers to thrive (Navratil 1991, Doucet 1989). Full sunlight to the forest floor best meets these requirements. However, young aspen suckers are susceptible to competition from other understory plants and herbivory from browsing ungulates (primarily elk and deer) even if abundant suckers are present. Having access to a well developed parental root system gives aspen sprouts a great advantage over other plants. The parent roots supply carbohydrates and access water deep in the soil profile allowing sprouts to grow rapidly, out-compete other vegetation, and withstand frequent droughty conditions in the West. Planting aspen in a non-irrigated location in a Colorado study was not successful (Shepperd and Mata 2005). Transplanting greenhouse or nursery-grown aspen seedlings into the field has similar problems to those of natural seedlings, indicating that the small root mass of transplanted seedlings is insufficient to absorb enough moisture to maintain the seedlings during periods of summer drought in the wild. Re-establishing aspen and serviceberry on reclaimed surface-mined lands is therefore problematic, since the parent root systems are destroyed when topsoil is removed. In contrast, transplanting sapling-sized aspen in irrigated urban landscapes has not been a problem, because the abundant supplies of water in lawns and landscape beds enable the transplants to thrive. Although aspen is somewhat tolerant of drought conditions (Lieffers et al. 2001), irrigation could benefit growth and survival of planted aspen stock, because moisture stress negatively affects aspen response to nutrient uptake (van den Driessche et al. 2003). Water deficit stress also reduces stomatal conductance, root hydraulic conductivity, and shoot leaf water potential in aspen (Siemens and Zwiazek 2003). Irrigation has been shown to increase growth of hybrid poplar, a closely related species (Hansen 1988; Strong and Hansen 1991). Herbaceous competition has been shown to reduce survival of aspen on reclaimed mined lands (Hughes et al. 1992). Serviceberry is common and important shrub in western ecosystems, and is an . important food source for wildlife, supplying both foliage for forage and fruit for