| Global warming has become an undisputed fact,and it would lead to the change of regional precipitation pattern.Especially drought with high temperature in the subtropical area will have significant impacts on nitrogen transformation in forest ecosystems in this region.In order to explore how soil warming and precipitation exclusion influence soil N2O fluxes,we used related functional genes as markers combined with high throughput sequencing,and four treatments were set up,viz.control,warming,precipitation exclusion,warming and precipitation exclusion interaction.In this paper,the main results were as follows:Warming and precipitation exclusion changed the soil nutrient availability.Warming increased the soil nutrient availability which could be absorbed by microorganisms easily.Precipitation exclusion mainly affected the N availability,with a significant decrease in soil ammonium nitrogen concentration.Warming had significant effects on microbial biomass carbon,nitrogen and phosphorus,which all decreased.It indicated that temperature played an important role in microbial nutrient utilization.Function prediction results also showed that after soil warming microorganisms prefer to use more decomposition material to maintain the energy activity,and the nutrient utilization efficiency of microbes was decreased.Warming and precipitation exclusion and their interaction could affect the microbial community structure,and the microbial community structure in different treatments were different from the control.The concentration of MBP and NH4+-N were the environmental factors which could significantly affect microbial community.Warming and precipitation exclusion and their interaction could affect microbial community structure through changing soil nutrient availability.Although warming and precipitation exclusion decreased the nitrification potential,but the effects were not significant.Warming and precipitation exclusion could significantly affect the abundance of AO A amoA.There are a significant positive correlation between nitrification potential and AOB abundance,while the correlation between AOA abundance,AOA amoA gene abundance and nitrification potential were not significant,which indicated that the contribution of AOA to soil nitrification potential may be less than that of AOB,although the AOA abundance was higher than AOB abundance.Because the abundance of AOB and gene were very low,other microorganisms,such as fungi,might play an important role in soil nitrification process.There were significant relationships between nitrification potential,microbial abundance and soil nutrients.Significant positive correlations between soil nitrification potential,AOB abundance and concentration of ammonium and MBC were found.While there were significant negative correlations between the AOA gene amoA abundance and concentration of ammonium nitrogen and MBC.There was no significant correlation between soil nitrification potential and soil N2O flux,which may be related to the low AOB community abundance and the weak contribution of AOA to nitrification.The changes of soil N2O flux were consistent with the denitrification potential.The denitrification potential in non-warming treatments(CT,P)were significantly greater than in warming treatment(W,WP).Warming and interaction of warming and precipitation exclusion had no significant effects on denitrification potential.High temperature might inhibit denitrification by increasing the soil redox potential,thus reducing soil N2O flux.Denitrification potential directly affected soil N2O flux,while MBP and warming treatments affected soil N2O flux indirectly by their direct influence on denitrification potential.Denitrifying microbial activity were influenced by MBP,and thus indirectly affect the soil N2O emissions.Phosphorus might be the microbial nutrient limitation factor for denitrification,and the effectiveness of P was significantly affected by temperature.Climate change mainly affected soil microbes and N2O fluxes by changing soil nutrient availability,and temperature and P availability were the main drivers and limiting factors in this region. |
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