Effect Of Simulated Climate Change On Forest Soil Microorganisms Based On Displacement Test

In recent years,the global climate change trend has become increasingly significant,and it has an important impact on forest ecosystems.As an important part of the forest ecosystem,soil microorganisms are one of the main driving forces in the biogeochemical cycle.They are very sensitive to the external environment changing,meanwhile global climate change may further enhance their sensitivity.Therefore,understanding the response of soil microbes to climate change is of great significance for in-depth understanding of the response mechanisms of forest ecosystems to climate change.Recently there are many studies on the influence of climate change on soil microorganisms at home and abroad,and most of them were indoor simulation control test,whose methods have small test space.Beside,it is dramatically different between indoor test conditions and wild environment,and insufficient representativeness and other issues.At present,there are some field simulation control experiments,such as burying cables in the soil to simulate soil warming,and these methods have the disadvantages of high research cost and large disturbance to the soil,and it is difficult to truly reflect the impact of climate change on soil microorganisms.However,the natural differences in climate and environment at different altitudes have been used in recent years.The undisturbed soil column displacement test can better simulate different climate conditions and overcome the defects of the above methods,so as to realize the study of the influence of climate change on the soil microorganisms under wild conditions.Therefore,this study takes the forest soil of Wuyi Mountain Nature Reserve as the research object,based on the field test of the undisturbed soil column displacement to simulate the climate change,using high-throughput sequencing technology to measure and analyze the soil bacteria and fungus under different treatments quantity and community structure,combined with relevant soil physical and chemical indicators,to explore the main driving factors,which affecting soil microbial community composition and activity.The soil microbial functional metabolism characteristics is characterized through analyzing the enzyme activities related to soil carbon,nitrogen,phosphorus and other nutrient cycles.Thus,revealing the response process and mechanism of soil microbes to climate change,with a view to providing basic data and theoretical basis for in-depth understanding of the response of subtropical forest ecosystems to global climate change.The main findings are as follows:1.Climate cooling and warming simulation has a noticeable impact on soil microbial community structure,significantly changing the species composition and quantity of soil bacteria and fungus.Among the in-situ control conditions,a total of 20 phylums,48 classes,67 orders,106 families,95 genera of bacterial species were detected;16 phylums,26 classes,56 orders,120 families,140 genera of fungus.Under simulated climate warming conditions,a total of 25 phylums,58 classes,81 orders,128 families,148 genera of bacterial species were detected;18 phylums,28 classes,69 orders,139 families,240 genera of fungus.Under simulated climate cooling conditions,21 phylums,61 classes,71 orders,124 families,117 genera of bacterial species;15 phylums,30 classes,67 orders,133 families,218 genera species of fungus.Different soil microorganisms have different sensitivities to climate change,so that different populations change their abundance and generate new strategies to cope with climate change.2.Soil microbial biomass was significantly affected by temperature and was closely related to soil environmental factors under different climate change conditions.Under the condition of simulated climate warming,soil temperature and MBC were extremely significant negative correlation(P<0.01),while MBN has very significant positive correlation(P<0.01),suggesting that climate warming significantly inhibits the accumulation of MBC,and significantly promote MBN accumulation,related to carbon,nitrogen cycle different microbes may make different responses to climate warming,resulting in the change of the microbial carbon and nitrogen is different;MBC content was significantly correlated with TC and TN(P<0.05)or extremely significantly negatively correlated(P<0.01),and positively correlated with NAG(P<0.01).There was a significant negative correlation between MBN and C/N(P<0.05).Under the simulated climate cooling condition,soil temperature was negatively correlated with MBC and MBN significantly(P<0.01),indicating that the content of MBC and MBN was significantly reduced by climate cooling.MBC content was negatively correlated with TN and TC(P<0.05)and extremely significantly(P<0.01),while MBN was negatively correlated with TC and C/N(P<0.05)and positively correlated with TK(P<0.05).3.Simulated climate change has a significant impact on soil fertility status.Under simulated climate warming conditions,soil TC,TN,and TP contents increased relatively,and there were inter-annual dynamic changes that decreased year by year,and TK contents decreased relatively.Under the conditions of simulated climate cooling,the soil TC,TN,TP content increased slightly,with the cultivating time,showing a decreasing dynamic trend,TK content decreased slightly,and there is an interannual dynamic change of first fall and then rise.The effect of simulated climate warming on soil fertility is significantly greater than that of simulated climate cooling,temperature changes.4.Redundancy Analysis shows that under simulated different climate change conditions,the main soil environmental factors that affect the soil microbial community structure are quite different.Under simulated climate warming,the main controlling factors affecting soil bacterial community structure changes are NAG,TP,βG and TK,while those affecting soil fungus include TK,TP,NAG,βG,TN and C/N;As for simulation in the cold climate,the main controlling factors affecting the variation of soil bacterial community structure are βG,C/N,TN,NAG,N/P,TC and TP,while the main controlling factors affecting soil fungus include TK,TC,βG,NAG and TN.Among them,NAG and βG have significant effects on soil bacterial community structure regardless of simulated climate warming or cooling,while TK,βG,NAG and TN have significant effects on soil fungus community structure.In conclusion,this study found that both increase and decrease in temperature contribute to noticeable influence on soil microbial community structure,and there is a more visible effect in warming stimulation,which indicates microorganisms have capabilities to make response to climate change positively,thus adapting to climate change gradually.Specifically,climate change lead to temperature variation in soils,restraining the accumulation of MBC,meanwhile,facilitating the accumulation of MBN.It can also improve soil fertility,which is greater under warming condition.It can be seen that climate change alters soil environment factors,leading to changes of soil microbial community structure.Moreover,these main-control factors influencing soil microbial community structure in forest vary from different climate change conditions.These conclusions have guiding significance for revealing the response mechanism of soil microorganisms to climate change,which provide basic data and theoretical support for in-depth research on the response mechanism of subtropical forest ecosystem and the protection of forest resources under global warming.