Response And Legacies Effect Of Microbial Community And Function Following Drought And Freeze In Desert Soils

Desertification is one of the most severe forms of land degradation in the world resulting in reduced vegetation cover and soil quality.Climate change also affects the response of soil microbial communities and functions to subsequent climate which is called legacy effect.However how these disturbances affect the microbial community and function of desert soil and the subsequent legacy effects remain to be studied.Nutrient is one of the main driving factors of soil microbial growth.In barren desert ecosystems it is not clear whether nutrient addition affects the response of soil microbial to extreme climatic disturbances.In view of the above problems this study took the arid desert ecosystem soil in Gansu Province of China as the research object.We simulated three disturbances(drought freezing and freeze-drought)to explore the effects and legacy effects of extreme climate on desert soil microbial and ecosystem functions.The changes of soil microbial community composition diversity and functional genes were analyzed by high-throughput sequencing and quantitative PCR and ecosystem functions such as soil enzyme activity basic respiration and nitrogen mineralization were measured.The effects of extreme climate on desert soil microbial and ecosystem functions and their legacy effects were explored.In addition the nutrient addition experiment before and after the disturbance revealed that soil nutrients regulated the resistance of soil microorganisms to climate disturbance.Our results show that:(1)Climatic disturbance caused legacy effects on microbial community composition that attenuated responses to subsequent disturbances and these effects were stronger in prokaryotes.The legacy effect of soil microbial community also affected the response of soil multifunctionality to late drought and freezing.We found that the residual response of soil microbial community to the late disturbance was largely due to the fact that nearly half of the changed taxa had been affected by the early disturbance so the response to the secondary disturbance tended to be stable.And these response groups are phylogenically conservative and negative response groups are more conservative which may be the result of adaptation to historical disturbances.In addition,we found that changes in community composition caused by climate disturbance also influenced changes in soil function reflecting the role of microbial community in maintaining function under disturbance.These results indicate the legacy effects of various climatic disturbances on desert soil microbial communities and highlight the key role of microbial communities in mediating soil functional responses to climatic disturbances.(2)The experimental results of nutrient addition showed that increasing soil nutrients before disturbance would reduce the influence of disturbance on microorganisms and improve the complexity of microbial co-occurrence network while increasing soil nutrients after disturbance would reduce the stability of microorganisms indicating that nutrient addition before disturbance increased microbial resistance to disturbance.For microbial communities,nutrient addition before disturbance increased the abundance of tolerant taxa and tolerant taxa improved the resistance and multifunctionality of microbial communities.Except for nutrient addition before disturbance there was a significant relationship between microbial diversity and ecosystem function under other treatments but the relationship was decoupled by nutrient addition before disturbance.Further analysis of the driving factors of multifunction showed that "opportunistic" taxa tolerant taxa and community resistance in response to disturbance all contributed significantly to multifunction.In summary,the effects of extreme climate disturbance on soil microbial community in desert ecosystems were studied in this paper.It was found that the legacy effects of soil microbial community under climate disturbance were mainly due to the selection of microbial taxa by the initial disturbance and that soil microorganisms showed phylogenetic conservation and environmental adaptability to the disturbance.In addition nutrient addition before disturbance improved microbial resistance to climate disturbance thus promoting the function of soil microorganisms.This study provides a theoretical basis for improving the stability of desert soil ecological environment.