Abstract:A field experiment was conducted in Acacia auriculaeformis plantation at the Heshan Hilly Land Interdisciplinary Experimental Station to investigate the short-term effects of earthworm (Ocnerodrilus occidentalis) and plant (Evodia lepta) on soil N2O and CH4 fluxes. The N2O and CH4 fluxes were measured in situ using the static chamber technique and analyzed with gas chromatogram for 15 days. The results showed that E. lepta did not significantly enhance soil N2O and CH4 fluxes, but fake plant (to simulate the physical effects of E. lepta) significantly increased soil N2O emissions (P<0.05). Earthworm promoted soil N2O fluxes in both control (without plant or fake plant) and the treatment with E. lepta by 26.7% and 66.3%, respectively. Contrary to our hypothesis, the effects of additional earthworm on soil N2O fluxes were not always positive. In the treatment with fake plant, the earthworm effects decreased the N2O fluxes by 39.7%. Meanwhile, the earthworm increased the CH4 uptake by 10.3% in control, but decreased the CH4 uptake by 90.6% in the treatment with fake plant and decreased CH4 uptake by 301.8% in the treatment with E. lepta. Earthworm addition shifted the soil CH4 from uptake to emission in the treatment with E. lepta and significantly decreased soil CH4 uptake in the treatment with fake plant (P<0.05). The results indicated that earthworm could accelerate soil N2O emission and might even convert CH4 sinks into sources in the A. auriculaeformis plantation. The physical effect of E. lepta facilitated soil N2O emission, while the biological processes of E. lepta might suppress soil N2O efflux. No significant correlations between N2O as well as CH4 fluxes and hydrothermal factors were found in the present study. In order to reduce the soil greenhouse gas emission, it will be useful to consider both the independent and interactive effects of plant physical processes, plant biological processes and earthworm activity on the efflux and influx of soil greenhouse gases.
