Climate change is expected to have major effects on the composition of ecological communities, but the magnitude and directionality of community change may vary, even when communities are exposed to similar changes in environmental conditions. In the Sonoran Desert, the relative abundance of cold-adapted winter annual plant species has increased as a result of shifts in the timing of winter precipitation. However, long-term directional change in community composition has yet to be studied in this system. Here, we use non-metric dimensional scaling and permutation-based statistical comparisons to quantify the directionality and magnitude of community change in a long-term winter annual abundance dataset collected at Tumamoc hill in Tucson, Arizona. This dataset includes species abundance data for plots located under shrubs (“shrub plots”) and in open habitat (“open plots”). Specifically, we ask if has there been significant change in the composition of the community as a whole, and if so, has it been directional? We also ask if both plot types exhibit similar change, and if community shifts appear to be related to changing selective pressures on functional traits
Results/Conclusions
Between 2000 and 2016, we found that community composition differed between open and shrub plots. Both exhibited significant change over this time period, however, this change was directional only in open habitats. Our results indicate that climatic differences between years have a stronger impact on the community at open sites. Inherent trait differences between these two communities may provide a possible mechanistic explanation for the changes experienced by each community.