Background/Question/Methods From 1949-1951, Robert Whittaker sampled over 600 sites in the Klamath-Siskiyou Mountains, OR in order to understand how environmental gradients affect plant community composition.  This study region has experienced an increase in annual temperature of 2 C over the past 57 years.  In 2007, we resampled these sites using identical methods to evaluate how climate change may have impacted these communities over time and to evaluate how community change on special soils (i.e., serpentine) compares to change in plant communities on normal soils. 

Results/Conclusions Using species traits and community ordination techniques, we found changes in the understory community that were consistent with climate change.  Herb cover has dramatically declined, especially for species with high specific leaf areas (SLA) and northern biogeographic affinities.  This has resulted in communities that are composed of more species associated with drier and warmer habitats (e.g., southerly slopes).  Our results suggest that the flora in this biodiversity hotspot has experienced dramatic declines and that species associated with special soils may be at extreme risk from climate change.  Monitoring change over time in the floras associated with these unique soil types and measuring species traits may provide important information for predicting species distribution shifts and the efficacy of conservation tools such as managed relocation.