Responses of a soil mollusk community to an extreme cold event

Soil communities are impacted by increasingly frequent and intense climate extremes. To accurately predict the effects of these events on soil communities and effectively design recovery and management programs for soil biodiversity, it is necessary to understand the spatiotemporal patterns and mechanisms underlying the soil community responses. Here, we investigated a mangrove soil macrofaunal (mollusk) community before and after an extreme cold event (ECE) to determine the effects of the ECE on the spatial pattern, temporal succession, and deterministic and stochastic processes affecting the soil metacommunity. We used distance-decay and time-decay analyses to characterize the spatial pattern and temporal succession of soil mollusk community dissimilarity (e.g., species identity, abundance, and biomass) across a reginal scale (~350 km scale). We used null models to compare the relative importance of deterministic and stochastic processes in shaping the regional soil mollusk community assembly. The ECE resulted in a reorganization of the soil mollusk metacommunity reflected by the mortality and extinction of several original species, colonization by new opportunistic species, and a significant reduction in mollusk abundance and biomass. The ECE increased divergent temporal succession but decreased spatial segregation in the soil mollusks, consistent with changes in the community dissimilarity of species abundance, richness, and biomass. The ECE increased the numbers of non-random segregated and random structures of soil mollusks while decreased the number of non-random aggregated communities. Notably, non-random segregated communities were the most strongly affected. Thus, the response of the soil mollusk metacommunity to the ECE was mediated by an increase in limiting similarity processes and stochastic processes and a decrease in limiting dissimilarity processes. The dominant limiting similarity processes involved species competition and/or dispersal limitation. More broadly, our study indicated that alterations in the spatiotemporal dynamics of soil fauna in response to climate change should be studied at the metacommunity scale. These spatiotemporal dynamics should be further tested in an ecological processes framework to reliably evaluate soil community responses to climate change and to devise management strategies for global soils.