COS 22-8 - Temporal stability in California grasslands

Tuesday, August 9, 2011: 10:30 AM
8, Austin Convention Center
Barbara M. Going, Ecology, Evolution, and Marine Biology, University of California, Santa Barbara, Santa Barbara, CA, Brian L. Anacker, Department of Evolution and Ecology, University of California, Davis, Davis, CA and Susan Harrison, Department of Environmental Science and Policy, University of California, Davis, CA

Given the current rate of climate change and the limited resources available for conservation; it is imperative that we prioritize our efforts based on the vulnerability of communities and ecosystems.  Large differences are expected among communities in the magnitude, rate, and direction of their responses to climate change, based on factors such as microclimate, substrate, and species functional traits.  In particular, resource-poor, low productivity habitats like serpentine soil may be more resistant to climate change because they host stress-tolerant species that likely respond to change slowly.  At the same time, such habitats may be more sensitive to climate change if the relatively sparse community limits the ability of vegetation to buffer changes in temperature or precipitation. We use 10 years of community composition data from 38 serpentine and 42 non-serpentine grassland plots to assess if serpentine and non-serpentine habitats differ in temporal stability and if compositional turnover is related to variation in precipitation.  In addition, we relate patterns of stability to functional traits, including specific leaf area, leaf water content, and leaf nitrogen content, in serpentine and non-serpentine communities.


Our results indicate that variation in species composition is related to patterns of precipitation and that serpentine grasslands are generally more stable over time than grasslands on non-serpentine soil.  We found that variation in diversity closely tracks variation in precipitation on both soil types, but this relationship was weaker in serpentine soils.  When we considered all species, compositional turnover was higher in serpentine than in non-serpentine plant communities.  Interestingly, once annual grasses were removed, turnover was significantly lower for serpentine grasslands, suggesting that annual grasses may destabilize some plant communities. Analysis of trait data indicated that serpentine and non-serpentine grasslands differ in the distribution of functional traits and that serpentine species tend to be more stress-tolerant.  For example, specific leaf area (SLA) was significantly lower in serpentine than in non-serpentine communities.  In addition, variation in diversity and temporal turnover (excluding annual grasses) was significantly and positively correlated with cover-weighted SLA.  These results suggest that the functional traits of species occupying stressful habitats may confer some resistance and that serpentine communities may be slower to respond to changes in climate, particularly precipitation.

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