Investigating Microbial Adaptive Strategies Of Forest And Agricultural Soil On Habitat Change

Soil microorganisms as important drivers and participants in matter cycling and energy flow in terrestrial ecosystems,which can regulate the feedback of soil organic matter to climate change by changing microbial extracellular enzyme activity or microbial community structure.There exist significant differences in soil organic carbon and microbial community structure between forest and cropland ecosystems.Therefore,it is possible to clarify the soil microbial communities to habitat climate change and the important role of microbial extracellular enzymes on regulating soil matter cycling in order to predict the response of ecosystems to changing environmental conditions.Here,soil translocation experiments were set up between forest and cropland ecosystems at the same latitude in the northern of China.Firstly,our study explored the influence of habitat changes on microbial biomass using phospholipid fatty acids analysis and identifying the main soil factors;Second,combined with high throughput sequencing method,we further investigate the microbial response strategy in forest and cropland to habitat by analyzing microbial species richness,ecological niche width and so on.Finally,we clarified the interaction between soil extracellular enzyme activity and microbial response strategies,as well as soil factors under the background of climate change with soil enzyme activity analysis.The results are as follows:(1)After forest soil translocated to cropland ecosystem led to a significant decrease in the biomass of gram-negative bacteria,grampositive bacteria,bacteria,fungi and actinomycetes(P <0.05).soil moisture content,available carbon and nitrogen are the main factors affecting the soil microbial community structure.Cropland soil translocating into forest ecosystems increased the soil available resources.However,the microbial biomass did not change significantly.For both forest soil and cropland soil microorganisms,habitat changes did not change their vertical structure of microbial mass decreasing with soil depth,and the sensitivity of microbes in subsoil to environmental changes was greater than that of the topsoil(P <0.05).(2)Forest soil translocated to cropland ecosystem decreased available resources,and changed dominant species abundance which can lead to the changes in microbial community structure,and the pan-species with stronger resource competitiveness increased in the entire microbial community niche,leading to the overall ecological niche of microbial community becoming wider to obtain the required resources for surviving.Cropland soil translocated to forest habitat increased available resources,decreased the proportion of bacterial generalized species in the bacterial community niche,resulting in narrowing of the bacterial community niche and selective utilization of environmental resources.In both forest soil and cropland soil,habitat change did not change the characteristics of microbial niche narrowing with soil depth,and lower ecological niche made the microbial community with less resistant to habitat change(P<0.05).(3)Soil extracellular enzyme activity was affected by soil nutrient availability,microbial community composition and substrate content.Forest soil translocated to cropland habitat that changed microbial community structure,leading a decrease in carbon and phosphorus converting enzyme activities.Therefore,the activities of carbon and phosphorus related enzymes decreased.After the cropland soil was translocated to forest habitat,there was no significant change on soil microbial community structure,and the increase of soil available nutrient content inhibited extracellular enzyme secretion,further decreasing hydrolytic enzymes activities.The translocation of forest and cropland soil significantly decreased carbon,nitrogen,and phosphorus related enzymes activities with soil depth(P <0.05).There was no linear relationship between enzyme stoichiometry and soil stoichiometric ratio in topsoil,however,there was a linear relationship between enzyme stoichiometrc and soil stoichiometric ratio in subsoil,indicating that microorganisms in subsoil were more affected by nutrient restriction.On the one hand,there are fewer microorganisms in subsoil that secretes less extracellular enzymes.On the other hand,lower content of large molecular substrates in subsoil inhibited the secretion of extracellular enzymes.These results indicated that the response strategies of cropland and forest soil microorganisms to habitat changes were different,and the subsoil microorganisms are more sensitive to habitat changes.Microorganisms can adapt to habitat changes by adjusting the microbial community structure and the secretion of extracellular enzyme.