Beta diversity, or variation in community composition, can arise from changes in local diversity and species’ responses to environmental variation. Although numerous studies have considered the effects of climate change on local diversity, their impacts on beta diversity remain understudied. Here, we test how experimental warming and reduced rainfall impact the beta diversity of grassland plants.
We used data from a factorial warming and rainfall reduction experiment at Cedar Creek Ecosystem Science Reserve. In 1994, nine 9 x 9m plots were planted with 16 grassland plant species. Subsequently, in subplots, a warming treatment was added in 2009 and a rainfall reduction treatment was added in 2017. All four combinations of warming (ambient or + 1.5 °C) and rainfall reduction (ambient or reduced by 43%) were included in each of the replicate 9 x 9 m plots, randomized to 2.5 x 3m subplots. From 2017 – 2019, aboveground plant biomass was harvested from clip strips in each subplot, and sorted to species.
Results/Conclusions
A decade of warming decreased local plant species richness and increased local dominance, especially by a C4 grass, Andropogon gerardii. Warming also decreased beta evenness, as many replicate communities converged on dominance by this grass. Three years of rainfall reduction marginally significantly reduced beta diversity. The rainfall reduction treatment, which started more recently than the warming treatment, may eventually shift the plant community toward increased dominance by A. gerardii, which would reinforce the effects of warming in these grassland plant communities. These findings provide new insight into how climate ultimately impacts the structure and function of prairie ecosystems.