Influences of temperature and moisture on abiotic and biotic soil CO₂ emission from a subtropical forest

Soil CO₂ efflux is considered to mainly derive from biotic activities, while potential contribution of abiotic processes has been mostly neglected especially in productive ecosystems with highly active soil biota. We collected a subtropical forest soil to sterilize for incubation under different temperature (20 and 30 °C) and moisture regimes (30%, 60 and 90% of water holding capacity), aiming to quantify contribution of abiotic and biotic soil CO₂ emission under changing environment scenarios.

Results showed that abiotic processes accounted for a considerable proportion (15.6-60.0%) of CO₂ emission in such a biologically active soil under different temperature and moisture conditions, and the abiotic soil CO₂ emission was very likely to derive from degradation of soil organic carbon via thermal degradation and oxidation of reactive oxygen species. Furthermore, compared with biotically driving decomposition processes, abiotic soil CO₂ emission was less sensitive to changes in temperature and moisture, causing reductions in proportion of the abiotic to total soil CO₂ emission as temperature and moisture increased.

These observations highlight that abiotic soil CO₂ emission is unneglectable even in productive ecosystems with high biological activities, and different responses of the abiotic and biotic processes to environmental changes could increase the uncertainty in predicting carbon cycling.