OOS 2-4
A photo chronosequence of passive restoration in riparian and wetland areas at Hart Mountain National Antelope Refuge
Hart Mountain National Antelope Refuge (HMNAR) was founded in 1936, and the 101,000 hectare refuge was grazed by domestic livestock from the 1870s until their exclusion in 1990. Just prior to removal, photopoints were taken at various riparian and wetland locations throughout the refuge to document degradation due to domestic livestock. The objective of this research was to re-locate and re-photograph these photopoints, collect associated stream channel data in the riparian systems, and estimate the change in channel width and depth with and without livestock. I selected photopoints (N=23) to re-photograph based on several criteria: (i) sufficient distinct background features necessary to allow relocation, and (ii) evidence of degradation. Of the 23 photopoints, 12 pairs of stream channel data (riparian systems) could be quantified using field data (current) and images (historical and current).
Results/Conclusions
In historical photos of the riparian areas very little native vegetation is evident, bare ground cover is high, the vegetation is trampled, and the stream channel is highly eroded. In contrast, current images of the photopoints show: a reduction in exposed bank, a return of stream side vegetation including willows (Salix spp.), and a widening of riparian vegetation. In the historic photos of the wetlands the ground is bare and disturbed. In the current photopoints vegetation has returned and the total area of the wetland has increased. In the uplands there is encroachment of Western Juniper (Juniperus occidentalis) evident in some photos. Over twenty years of cattle exclusion has lead to dramatic changes in stream channel width to depth ratio. The mean width to depth ratio of the remnant channel was found to be much higher (mean 11.3, SD 4.83) than the current channel's ratio (mean 3.8, SD 1.84, p= 0.001).