Interactive effects of temperature, soil moisture and enchytraeid activities on C losses from a peatland soil

Abstract Recent evidence indicates that our current soil C stores may be already changing from carbon sinks to sources, with reported increasing C losses in both gaseous (soil respiration) and aqueous (dissolved organic carbon, DOC forms) across large areas of the Northern Hemisphere. Current debates have mainly focused on climatic variables; however, accounting for the abiotic and biotic interactions is required to enable better quantifications of C dynamics. Therefore, in this study, we investigated the interactive effects of temperature, moisture and dominant mesofauna (enchytraeids) changes on C losses by incubating root-free sieved soil samples from a peatland soil during 13 weeks at two temperature (14 and 19 °C) and two moisture (85 and 60% WHC) treatments under laboratory conditions. Our results showed that neither temperature nor moisture and invertebrates had a significant effect on respiration rates. In contrast, under favourable moisture conditions, the temperature induced changes in enchytraeid population numbers resulted in more DOC being released from these soils, possibly linked to the positive effects of animal activities on iron mobilisation and buffering the pH of the soil solution. Our results also confirmed that moisture contents of 60% WHC could severely affect their population numbers in these organic soils and hence, the functioning of these vulnerable ecosystems. Importantly, in agreement with previous studies, availability of easily accessible C sources seems to be a critical factor in the progressive declines of soil respiration and DOC production rates over time. Taken these findings together it is possible to conclude that the combined action of abiotic factors and their influence on soil fauna populations plays a key role in controlling SOM decomposition rates of these peatland soils.