We ask whether plant communities in sites that have had a history of logging are at heightened risk of extinction from climate change relative to those that have remained unlogged.  We assess these interacting effects by resampling plant communities originally sampled by Robert Whittaker from 1949-1951 in the Klamath-Siskiyou mountains in Oregon. 
Results/Conclusions

Consistent with a warming climate, plant communities have shifted toward a more xeric species composition (i.e., more like that of a south-facing site) since Whittaker sampled them.  In addition, communities at sites logged since Whittaker’s time have shifted significantly more strongly toward a more xeric species composition than those that were not logged.  We also consider the possible effects of other impacts, such as fire suppression.  Our results suggest that the interactions among multiple global change factors may have detrimental effects on plant community diversity.