Effects Of Long-term Greenhouse Cultivation On Soil Functions And Microbial Communities In A Subtropical Agricultural Ecosystem

In recent years,with the increasing population in China,the area of greenhouses has expanded rapidly,and long-term greenhouse cultivation can lead to soil salinization and adversely affect agroecosystem function(e.g.crop yield).However,so far,the effects of long-term greenhouse cultivation on soil functions(e.g.soil respiration,soil labile organic carbon and nitrogen content),soil microbial community structure and diversity in subtropical agroecosystems are unclear.Based on this,this thesis relied on the control sample plots,8-year mid-term greenhouse planting sample plots and 21-year long-term greenhouse planting sample plots in Fengxian District,Shanghai to conduct experiments.Soil respiration observations were conducted in the field for six months,and soil samples were collected to analyze soil microbial activity and soil physicochemical properties(e.g.labile organic carbon,nitrogen content),and highthroughput sequencing and microbial ecological networks were used to explore the changes in microbial community structure,diversity and key microbial taxa.The main results are as follows:(1)Compared with the control,long-term greenhouse cultivation significantly increased soil salt content,formed soil salinization,reduced crop yield and soil respiration rate,and suppressed soil microbial activity,thus promoting the accumulation of soil labile organic carbon and nitrogen content.(2)Long-term greenhouse cultivation significantly changed the soil microbial community structure: the relative abundance of Gram-positive bacteria(e.g.Actinobacteria,Firmicutes)increased and the relative abundance of Gram-negative bacteria(e.g.Nitrospirae,Proteobacteria)decreased.However,there was no significant effect on microbial diversity.Further analysis revealed a significant correlation between soil function and relative abundance of bacteria,indicating that long-term greenhouse cultivation caused significant changes in soil function by altering the structure of the microbial community.(3)The results of microbial ecological network analysis showed that long-term greenhouse cultivation significantly reduced soil microbial network complexity and community stability,and identified keystone species(e.g.Burkholderia).We inoculated the selected Burkholderia into the long-term greenhouse plots and found that inoculation of these keystone species increased crop yield and significantly increased the modularity and community stability of the microbial ecological network.In summary,long-term greenhouse cultivation leads to soil salinization in subtropical agroecosystems,decreasing soil functions such as soil respiration and soil microbial activity,and increasing soil labile carbon and nitrogen content,whose microbial mechanisms lie in lower soil microbial network complexity and community stability.In addition,inoculation of keystone species improved crop yield and enhanced soil microbial community stability,confirming the importance of microbial ecological network analysis in agroecological restoration.Our results provide a theoretical basis for the sustainable development of agroecosystems in subtropical greenhouses and greenhouses.