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Title: Long term vegetation change in California Park: Evidence for alternate states?

Author
item Kachergis, Emily
item ROCCA, MONIQUE - Colorado State University
item FERNANDEZ-GIMENEZ, MARIA - Colorado State University

Submitted to: Society for Range Management Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 10/25/2011
Publication Date: 1/31/2012
Citation: Kachergis, E.J., Rocca, M.E., Fernandez-Gimenez, M.E. 2012. Long term vegetation change in California Park: Evidence for alternate states?. 65th Annl Society for Range Management mtng. January 28-February 3. Spokane, WA. Abstract #0174.

Interpretive Summary:

Technical Abstract: Understanding shifts in ecosystem state is a frontier in ecology with important implications for land management and human well-being. The goals of this study are 1) to describe long-term vegetation change in a high-elevation sagebrush steppe park (California Park, Colorado) and 2) evaluate evidence that this ecosystem exhibits alternate state dynamics. We examined change in species composition over 50 years (15 permanent transects, six sites) and related it to management and climate drivers using non-metric multidimensional scaling. We found that species composition has changed over time in response to management but not climate. Spraying herbicide resulted in short-term increases in native palatable grasses and forbs and decreases of shrubs and the dominant, unpalatable forb mule’s-ears. Native grasses have since decreased again and shrubs have recovered, coincident with increases in cattle stocking rate and elk populations. The non-native pasture grass timothy has become a dominant grass in California Park. Changes in species composition generally did not match alternate state dynamics. Instead of sudden, large, persistent shifts, composition changes were small and gradual and fluctuated through time. Two possible exceptions are 1) lack of recovery of the dominant forb mule’s-ears after spraying, possibly indicating a shift from a state induced by overgrazing and 2) the recent increase in the non-native grass timothy. Long-term changes in species composition suggest that vegetation in California Park changes gradually in response to management rather than shifting suddenly between alternate states. The increase in timothy raises the question of whether gradual changes can still be irreversible.