Research On Driving Factors Of Forest Soil Methane Absorption Under Climate Chang

Forest soils are the most effective terrestrial biosink for atmospheric methane（CH₄）.Global changes such as increased atmospheric CO₂ concentrations,warming,altered rainfall patterns and increased nitrogen deposition affect soil CH₄ uptake by influencing soil physicochemical properties,plant growth and soil microbes.In recent years,there has been an increasing number of studies on the effects of global change factors on CH₄ uptake in forest soils,but the response mechanisms of CH₄ uptake in forest soils to global change are still not fully understood.Thus,this paper firstly analyses the potential effects of global change factors on CH₄ uptake in forest soils through Meta-analysis based on data from published articles in different regions of the world.Then,we investigated the changes in soil methane uptake at different N addition levels in different forest types with different soil layers in Dinghushang.We also analysed the changes in soil CH₄ uptake rates and their drivers under different moisture gradients in monsoon forest soils under drought treatment.The main findings are as follows:（1）Meta-analysis revealed that the rate of CH₄ uptake by forest ecosystems decreased significantly under elevated CO₂ and N deposition,but increased under drought.This study did not find significant differences in CH₄ uptake rates on an annual scale in tropical,temperate,and boreal forests.Moreover,the results of seasonal and drought experiments on forest soil CH₄uptake suggested the importance of soil moisture,but the linear model of CH₄ uptake in soil water balance fitted in this study did not reflect the negative correlation between soil water surplus and soil CH₄ uptake.（2）The analysis results of the experimental data from the Dinghu Mountain literature show that N addition has a facilitating effect on the soil CH₄ uptake rate in Sargassum pine forests,while it has an inhibiting effect on mixed forests and monsoon forests,with a higher tendency in monsoon forests.The soil CH₄ uptake rates model with different N additions fitted better.The total phospholipid fatty acid（PLFA）biomass,bacterial PLFA biomass and fungal PLFA biomass of soil microorganisms in monsoon forest showed decreasing changes under the drought treatment in Dinghushan.The effect of drought treatment onβ-galactosidase andβ-glucosidase was significant（p<0.05）.（3）At the beginning of the incubation period,the soil CH₄ uptake rate of the control group was bigger than that of the drought treatment group,the difference in soil CH₄ uptake rate between the drought treatment and the control group was significant for the 40%moisture gradient（p<0.05）.The difference in soil CH₄ respiration rate between the drought treatment and control soils at different soil layers and moisture gradients showed an increasing trend,and the difference between t drought treatment and the control was significant（p<0.05）in the 60%moisture level at the end of the incubation period.Soil microorganisms had a greater influence on the rate of CH₄ uptake,and the correlation between them increased as the moisture gradient increased.