Large Mammalian Herbivores, Plant Interactions, and Ecosystem Processes in Five National Parks

Singer, Francis; Zeigenfuss, Linda

Deciduous shrubs of wooded riparian areas may be declining in Wind Cave National Park (WICA). It is theorized that encroachment of Ponderosa pine as the result of fire suppression and heavy utilization of shrubs by elk are contributing to this decline. Using large fenced exclosures and prescribed burning, we investigated the impacts of these factors on shrub production and regeneration. Four hypotheses were proposed: (1) Fire suppression has led to the decline of shrubs in woody draw communities, and conversely reintroduction of burning will lead to an increase in shrub production and regeneration. (2) Excessive grazing has an effect on the production and regeneration of shrubs. (3) hot fall burns (fall vs. spring) have a greater effect on production and regeneration of shrubs. (4) some combination of these two factors (grazing and fire suppression) is responsible for the decline in shrub production in woody draws. Burning reduced shrub canopy volume in areas open to browsing/grazing immediately following burning, but increased regeneration of elm and box elder. Herbivory on shrubs in burned plots increased in the summer and winter following burning, particularly on spring burns. Fall burning had a greater impact than spring burning, increasing canopy volume, area and production of Rosa spp. and Ribes aureum, but suppressed height and growth compared to spring burns. The combination of burning and grazing led to significant decreases in canopy cover, particularly on spring burns. Results suggest that fall prescribed burning could be used to increase regeneration in riparian areas of WICA, but that provisions should be made to keep browsing intensities low immediately following burning.

Large Mammalian Herbivores, Plant Interactions, and Ecosystem Processes in Five National Parks

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