Environmental variability has differing impacts on salt marsh community diversity and stability
Environmental variability and the frequency of extreme events are predicted to increase with climate change. It is especially important to understand the effects of this change in salt marshes because, as climate changes, their continued ability to provide protection against storm surges and flooding will become increasingly important. Despite that, the role of environmental variability in shaping community composition, diversity and function is not well understood. Identifying current patterns of association between measures of community function and climatic means and variability will help elucidate the ways in which altered variability and mean conditions may change communities in the future. We used long-term plant community data from salt marshes along both coasts of the continental United States to determine the associations among environmental variability on different timescales, community stability and diversity.
We found that the mean and seasonal variability of temperature and precipitation were related to salt marsh community stability, but interannual variability was not. Species richness was negatively associated with mean precipitation but not variability. The strength of these effects differed on the east and west coasts of the United States, although the direction of the trends was often the same. These results indicate that salt marsh community stability and species richness are both likely to be affected by changes in precipitation means but not variability. Differences in seasonal variability in temperature will likely affect stability and not diversity. Changes in environmental variability and mean conditions are therefore likely to have important but distinct effects on communities. A better understanding of how variation on different timescales affects both community diversity and stability in other ecosystems will be necessary to forecast the future of biodiversity in a changing climate.