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Beta Diversity



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Journal of Ecology 2006 94 110 117 Beta diversity and the scale dependence of the productivity diversity relationship a test in the Californian serpentine flora Blackwell Publishing Ltd SUSAN HARRISON KENDI F DAVIES HUGH D SAFFORD and JOSHUA H VIERS Department of Environmental Science and Policy University of California Davis Davis California USA and USDA Forest Service Pacific Southwest Region 1323 Club Drive Vallejo CA USA Summary 1 The relationship of productivity to species diversity is usually positive at regional scales but is often neutral unimodal or negative at local spatial scales Recent studies have pointed out that beta diversity or among locality and within region variation in species composition must therefore tend to increase with productivity 2 We tested for a positive relationship of productivity to beta diversity in herbaceous plants at 105 widely distributed sites on serpentine soil in California We also asked whether any such pattern could be explained as previously proposed by increased environmental heterogeneity at higher levels of productivity 3 We found that one measure of beta diversity the species dissimilarity between paired 500 m2 plots on adjacent north and south slopes was positively related to productivity as measured by the normalized difference vegetation index a remotely sensed index However this effect was not strong enough to transform the neutral relationship of productivity with alpha 1 m2 diversity to a positive relationship of productivity with gamma 1000 m2 diversity 4 The positive effect of productivity on beta diversity was not related to increasing heterogeneity in coarse measures of vegetation structure percentage cover of shade litter rocks moss bare soil animal disturbance We speculate that the effect may instead have a top down explanation higher beta diversity may be caused by the positive influence of productivity on the size of the regional species pool 5 Our study illustrates the principle of a scale transition in



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