PS 42-143 - Effects of altered precipitation on the structure of ecological communities: Preliminary results from an ongoing meta-analysis

Abstract: Climate change is a pervasive and growing global threat to biodiversity and the functioning of ecosystems. Changes in climate increasingly alter precipitation patterns, increasing the frequency of severe droughts and heavy precipitation events. Altered precipitation events can affect community structure by altering species richness, diversity, evenness, and shifting species interactions. These effects can vary among taxonomic groups and trophic levels, however our understanding of the mechanisms underlying these distinct responses is limited. To date, synthetic studies on the effects of precipitation changes have been largely focused on their effects at the organismal level or on specific ecosystem processes. Synthesis work on community-level responses to altered precipitation has been limited to selected trophic groups from particular habitats.

To elucidate general community-level responses as well as disentangle context-dependent responses to altered precipitation, we conducted a meta-analysis focused on plant and animal communities. We hypothesized that altered precipitation will affect community structure, with decreased precipitation (magnitude and frequency) reducing species diversity, abundance, and evenness of plants and animals, while increased precipitation will show opposing effects. In addition, we expect that changes in precipitation will shift species interactions via changing the strength and the sign of the interaction. We also expected that these responses will vary depending on functional groups due to their different sensitivity to precipitation changes. We conducted a literature search in the Web of Science (WOS) Core Collection Database to create a global database of precipitation effects on community metrics.

Our results showed that most studies were conducted in North America (48.28%), Asia (34.48%), and 17.24% in Europe. We found significant decreases in plant and soil invertebrate diversity in response to decreased precipitation. However, we did not observe significant effects of increases in precipitation. Even though plant communities seem to increase in diversity, soil invertebrates decrease in diversity as a response to increased precipitation. These results suggest that the magnitude and frequency of decreased precipitation negatively affects plants and animal communities differently by decreasing diversity. Increased precipitation can positively or negatively affect communities according to their trophic position and optimal conditions. Using meta-analysis approaches, we can identify and address knowledge gaps in community-level responses to precipitation changes and the underlying causes explaining variation on these responses. Our findings can be applied to real-world conservation, and policy-making as changes in community structure and functions are likely to affect ecosystem services and human well-being.