Debris Barriers Reduce the Effects of Livestock Grazing Along Streams After Timber Harvest

Abstract

Timber harvesting in riparian zones without leaving a buffer can increase the likelihood of livestock grazing along streams. The wet soil around small streams can accentuate the negative impact of grazing, affecting vegetation, as well as other ecosystem characteristics. In this study, we tested the effectiveness of using coarse woody debris, a readily available barrier method to reduce the effects of livestock grazing after timber harvesting on small stream vegetative and other ecosystem values over two grazing seasons. We placed debris barriers within four recently harvested cutblocks where livestock graze seasonally on extensive, forested rangeland in the Okanagan region of Interior British Columbia, Canada. We sampled cover, species richness, bare soil, litter, biomass, trampling, and manure within 0.25m2 quadrats to determine the effectiveness of the barriers on these variables over two grazing seasons. We used log response ratios to compare the pretreatment and post-treatment values of these variables in control plots and plots with debris barriers. We also used log response ratios to test the effect of debris barriers on biomass utilization within and outside 1-m2 cages. Results varied by site: debris barriers resulted in improved richness and litter in two sites each, reduced trampling in three sites, and reduced bare soil in one site when compared with plots without barriers. Barriers also increased cover in one site but had no influence on manure. Biomass utilization was significantly reduced by debris barriers in uncaged grazed plots compared with caged plots. Debris barriers can be a convenient tool to mitigate the potential negative effects of livestock grazing after timber harvest in and around small headwater streams.