Tolerance to fluctuating water regimes drives changes in mesofauna community structure and vertical stratification in peatlands

Abstract Peatlands are the largest natural carbon store as a result of environmental conditions that limit decomposition rates. However, climate change is predicted to threaten peatland C sink function through rising temperatures, lowered water tables and the expansion of vascular plants. Here, by selecting four peatland habitats differing in their dominant plant communities and abiotic conditions, we investigated the influence of the most relevant climatic factors (namely temperature and soil water content) in controlling the spatial and temporal responses of soil organisms and their potential links to above-ground plant functional diversity. We found that the soil mesofaunal communities under vascular plants were mainly dominated by microarthropods (oribatid mites and collembolans), and contrasted with those under mosses that consisted of enchytreids and dipterans (≈15% dissimilarity). We show that the balance of tolerance to drought and saturation determined the temporal dynamics and vertical stratification of the soil invertebrate populations. From this, we anticipate that the projected expansion of vascular plants not only will displace active peat forming vegetation species (mosses), but also those invertebrates that are poorly adapted to the new environment (enchytraeids and dipteral larvae). Our findings indicate future peatland responses to environmental changes should take into account the habitat complexity (above- and below-ground community structure) and the modulating effects of the abiotic environment.