Friday, August 7, 2009
Exhibit Hall NE & SE, Albuquerque Convention Center
Julie Ripplinger, School of Life Sciences, Arizona State University, Tempe, AZ and Thomas C. Edwards, Wildland Resources, Utah State University, Logan, UT
Background/Question/Methods Since at least the mid-1800s, humans have used shrubsteppe landscapes of the Intermountain West as rangeland. Issues associated with fire-suppression and overgrazing – e.g. increased shrub cover – have led to shrub-removal restoration treatments over the last 50-60 years. Legacy effects of human land-use alterations are poorly understood despite the fact that they can have substantial long-term economic and ecological implications. Accordingly, ecologists and land managers need an interdisciplinary assessment of these legacy effects in sagebrush steppe landscapes. We took a historical approach to this issue by using local ecological knowledge and government records to build a map of historical shrub-removal treatments. We then designed a factorial sample survey to investigate the legacy effects of shrub-removal across a continuum of historic-to-modern treatment sites. We measured vegetation change using species richness, Jaccard’s similarity and Simpson’s dissimilarity indices. These metrics were used to compare untreated, reference vegetation to modern, treated vegetation across a chronosequence of time since disturbance. Results/Conclusions
In general, results indicate that vegetation response trajectories are neither trending towards the state desired by management activities, nor recovering to a community composition predicted by state-and-transition models. On fire and chemically treated sites, we observed an increase in forb richness over time. However, this trend is not apparent on mechanically treated sites. All three treatment types showed increases in mean non-native grass richness. Our results suggest, at best, that vegetation response to treatment will be difficult to predict. Alternatively, our results challenge the validity of management assumptions implicit in shrub-removal treatments. Moving forward, it is critical that we continue our work with land management agencies and the local ranching community, as we integrate the results of this study into plans for sustainable landscape management in the future.
