The objective of this study was to quantify various overstory and understory plant community characteristics in the Populus forests on Elk Island National Park, Alberta, under different disturbance regimes. Vegetation from 36 sites, stratified by four topographic positions and three historical treatment combinations, of fire and native ungulate herbivory, were sampled. Results showed that the structure and production of vegetation within Elk Island National Park have been altered by intensive ungulate grazing and prescribed burning, although the effect of both disturbances is strongly influenced by topography. Ungulate herbivory inside the park has decreased the forest overstory and resulted in a shorter, denser shrub layer producing less browse. Prescribed burning has increased shrub densities and herb production, particularly at the crest topographic position. Vegetation production among components varied greatly between topographic positions, with changes in one or more growth forms typically offset by changes in others. In general, herbivory and fire within the park have combined to maintain a more open and patchy mosaic of Populus forest in contrast to the reference area outside the park, which is dominated by a more homogenous Populus forest.
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