Ungulate herbivory on Utah aspen: Assessment of long- term exclosures

摘要: The role of livestock grazing and big-game browsing in the decline aspen (Populus tremuloides Michx.) Intermountain West has long been questioned. All known exclosures (n=8) on Dixie Fishlake National Forests south-central Utah were measured during late summer 1995 1996 to determine stem dynamics, successional status, understory species composition. Five a 3-part design with total-exclusion portion, livestock-exclusion combined-use portion which permitted effects deer (Odocoileus hemionus) elk (Cervus elaphus) herbivory be separately from those livestock. Aspen within all plots successfully regenerated developed multi-aged stems without influence fire or other disturbance. subjected by wildlife, primarily mule deer, either failed regenerate at densities significantly lower (2,498 ha(-1)) than that (4,474 ha(-1)). On combined wildlife-livestock-use plots, most successfully, did so low (1,012 stems/ha(-1)). ungulate-use only when numbers low. Similarly, ungulate had significant In general, utilization tended reduce shrubs tall palatable forbs while favoring growth native grasses. addition grazing, however, grasses promoting introduced bare soil. Thus, communities dominated old-age single-age trees appear product browsing, not biological attribute as commonly assumed. There was no evidence climatic variation affected regeneration. Observed differences are attributed varied histories herbivory. DOI:10.2458/azu_jrm_v53i2_kay