Effects Of Warming On Soil Microbial Community Structure And Enzyme Activity In Alpine Forests

Climate warming had changed temperature and moistur of environmental factors,and then changed the land ecosystem matter and nutrient cycling,especially for high altitude eand high latitudes the ecosystem.Soil enzyme and microbe play key roles in the cycle of mass and energy fluxes of soil ecosystem.Soil microbes are sensitive to changes in environmental factors of climate change.The research on the biochemical process of soil is important in understanding the cycle of mass and energy fluxes of alpine ecosystem.Up to now,many experiments had been done to study soil microbial and soil enzyme responses of alpine forest ecosystems to simulated global warmingn,but the resule is different.Whether climate warming significantly change the content and comunty of soil microbes and activity of soil enzyme?What is the effect of climate warming on the water-soluble substances?Now this study still has a lot of uncertainty.In order to climate warming on soil microbial process,therefore,the alpine forest soil in western Sichuan was studied by natural environment gradient experiment.Soil cores beneath the alpine forest at 3900 m altitude were placed on the timberline ecotone at 4000 m.Soil microbial content and community,enzyme activity,enzyme stoichiometric ratio,soluble carbon,soluble nitrogen and soluble phosphorus in both soil organic layer(OL)and mineral soil layer(ML)were measured according to the critical period.The purpose of this study was to investigate the effects of environmental factors on the microbial community structure and soil enzyme activities in alpine forests about climate warming.Soil temperature increase with the increased altitude,the annual temperature in soil organic layer and in mineral soil layer increased 1.92 ? and 1.60 ? from 2014 to 2016.Snow thickness and freeze-thaw cycles were increased by elevation.Elevation had significant effect on SC,SP,SC/SN and SN/SP(p<0.01),but no significant effect on SN and SC/SP(p>0.05).The correlations between temperate and SN were very significantly negative(P<0.01).SC,SN and SP were significantly positive correlated with water content and freeze-thaw cycles(P<0.01).SC/SN,SC/SP and SN/SP were significantly negatively correlated with water content and freeze-thaw cycles(P<0.01).Elevation had no significant effect on fungi/bacteria,G+/G-,soil microbial biomass,bacterial content,fungal content,G+ content,G-content and micro eukaryotic content(p>0.05).Stage of sampling had very significant effect on fungi/bacteria,G+/G-,soil microbial biomass,bacterial content,fungal content,G+ content,G-content and micro eukaryotic content(p<0.01).The correlation between temperature and water content and soil microbes and fungi/bacteria very significantly positive(p<0.01).The correlation between freeze-thaw cycle and snow thickness and soil microbes and fungi/bacteria significantly or very significantly negative(p<0.01;p<0.01).Soil microbial content of FSF and GS is low freeze-thaw cycles and snow thickness is higher than SCS and SMS is high freeze-thaw cycles and the snow thickness.Elevation had very significantly affected on enzyme active of BG CBH,Lac,NAG,AP,LnBG/LnNAG and LnNAG/LnAP(p<0.01).Stage of sampling had very significant effect on soil enzyme activity and soil enzyme stoichiometry(p<0.01).Temperature was very significantly negative correlated with CBN,NAG,LnBG/LnAP and LnNAG/LnAP(P<0.01).The water content and freeze-thaw cycle were very significantly negative correlated with soil enzyme activities and LnBG/LnAP and LnNAG/LnAP(P<0.01).Snow thickness was a significant negative correlation between and BG and CBH(p<0.05).Lap,NAG and AP activity were decreased due to the warming of the climate.BG and CBH activities were higher in the period of high freeze-thaw cycle.In summary,the warming had a significantly affected soil enzyme activity,warming caused Lac,NAG and AP activity decreased in most of period.And the warming had no significantly affected soil microbial.Freeze-thaw cycles,snow thickness and temperature had significantly effect on soil microbial and soil enzyme activities.Therefore,climate warming had significantly effect on the soil microbial and soil enzyme activity.The correlation between soil microbial and soil enzyme activities significantly or very significantly positive(p<0.01;p<0.01).