The interactions between topography and grassland associations have shaped the many cultural land-uses of the Hells Canyon National Recreation Area (HCNRA) throughout history. In order to assess the long-term changes in vegetation across the HCNRA, we conducted a repeat study using 19 different sampling points within four plant associations of the Lower Imnaha Subbasin. The original study used plant cover and frequency data from a 1981 survey to describe the different seral stage classifications within each plant association. Using Nonmetric Multidimensional Scaling (NMDS) and Indicator Species Analysis (ISA), we were able to determine that the species composition of each plot was significantly different between the 1981 and 2014 sampling. ISA results show that plots within the later-seral stages tended towards a greater presence of key bunchgrass and forb species for that association, while earlier-seral plots tended towards exotic species dominance and reduction in native bunchgrass cover. Our findings demonstrate that the species composition shifts across the 33-year-time-period include a decrease in indicator species for each plant association, an increase in early-colonizer species, and an increase in exotic forb and grass species. Our results also show that many of the plots sampled have changed seral stages between 1981 and 2014, with many of them transitioning to early seral over time rather than moving toward later stages. The direction of these shifts appears to be highly dependent upon the slope and location of the plots. For example, shifts to earlier seral stages are most common on or near the benches. The topography within these canyon grasslands not only shapes the cultural land-uses within HCNRA in the past and the present but also the successional trajectory of its grassland communities. Â
Oral presentation and poster titles, abstracts, and authors from the Society for Range Management (SRM) Annual Meetings and Tradeshows, from 2013 forward.