After‑life legacy effects of enchytraeids increase the functional capability of arable soil following stress

Soil fauna plays irreplaceable roles in delivering ecosystem functions in the face of climate change and human activities. Understanding how soil fauna-mediated processes change following environmental stresses is therefore critical to the maintenance of ecosystem services. This study assessed the soil functional capability, as measured by short-term decomposition of plant residues, subjected to simulated copper and heat stress in the presence, or absence, of enchytraeids (Enchytraeus florentinus) in an arable soil. Results showed that enchytraeid density decreased to 37%, 10%, and 5% of the initial density at the end of the experiment in the control, copper, and heat treatments, respectively. Soil functional capability increased in the presence of enchytraeids, but only in the stressed soils and not apparently in the controls. Fungal biomass was increased in the presence of enchytraeids particularly in the control soil. The enchytraeids did not affect water extractable organic C (WEOC) and total extractable N (TEN) in the control; however, they increased TEN in both stressed soils and WEOC in the copper stressed soil. We found that the enchytraeid effects on functional capability were positively related to the proportions of dead enchytraeids throughout the experiment duration. We infer that the contribution of enchytraeids to soil functional capability was mainly due to the after-life effects, most possibly through three potential mechanisms including (1) enhancement of microbial activity with resource contributed from their dead bodies, (2) through microhabitat improvement established before their death, and (3) microbiome composition changes derived from live or dead enchytraeids. We conclude by our case as an example that soil fauna could sustain key ecosystem functions under adverse conditions, highlighting the importance of soil biodiversity conservation in a changing world.