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. e level is reached to prevent increasing flood hazards in a seeded area. c. Impacts on Plant and Animal Communities The impacts of snowpack augmentation on forest vegetation were studied in the San Juan Ecology Project [10], the Medicine Bow Ecology Project [14], and the Sierra Ecology Project [15]. In discussing the Medicine Bow Study, the Project Skywater Programmatic Final Environmental Statement states: "Few circumstances were found where snow accumulation appeared to be a limiting factor in forest ecology. One of these, it was suggested, was at some locations near tree line where ribbons of forest alternate with glades in which snow accumulates. The depth of snow, and the adverse effect of snow molds on survival of young trees, apparently serve to stabflize the boundaries of the glades. An increase in average wintertime precipitation might lead to an extension of the area where the glade-and-ribbon pattern prevails. On the other hand, in a New Mexico setting, the growth of spruce was found to be un i form in adj acent areas even though the average snowpack differed by a factor of more than eight. liThe conclusion was reached that a higher mean snow accumula- tion probably would not affect primary productivity unless ttle growing season was shortened." [2, p. 3-111J San Juan Ecology Study results agree with the Medicine 80'14 findings and state: "Bolewood production of spruce-fir stands was found to remain constant over a 20-year study period, and it was thought that productivity is mainly under genetic control. Tree biomass was shown to undergo severe perturbations attributable to catastrophic events such as windthrow, insect outbreak, or fire. It ~as considered deoatable whether changes in snowpack could positively or negatively influence these disturoance events. "Measurements of water stress in forest veaetation resulted in the identification of two periods of elevated stress, one immediately preceding snowmelt, the other later in the season, after the exhaustion of soil moisture held over from winter. If precipitation management were to extend :he date of moisture rei ease from snow cover, this mignt extend the duration of the spring period of moisture s~ress. The opinion ~as also expressea in :ne findings that the major effec: of this high-stress period ~ould be to reauce photo- synthesis rather than eel] division, since the trees were found able to rehydnt2 at night. As long as the st1"ess period ccc~rs before the beginning of phenological ~ctivity, . , 1..