Effects Of Soil Biological Crust On Soil Microbial Community Composition In Farmland Of Kangjin Tow

Research on biological soil crusts(biocrusts)has primarily concentrated on arid and semi-arid regions,the study in the agricultural fields of the black soil region of Northeast China is lacking.We found there were high biocrust coverage of 80-90% in the farmlands of Kangjin Town from preliminary surveys.Considering the essential biological functions of biocrusts,this study combined field surveys and laboratory analysis,with bare soil as the control,to explore the changes and dynamic characteristics of microbial indices in bare and biocrust soil.The research aims to provide a theoretical basis for the rational use of agricultural soil and the scientific management of biocrusts in the black soil region of Northeast China.The results were as follows:(1)The formation of biocrusts in the farmlands of the Northeast black soil region significantly increased the content of microbial biomass carbon,nitrogen,and phosphorus(MBC,MBN,MBP),improved soil phosphatase and urease activity,and the above of microbial indices correlated significantly with available potassium,available phosphorus,and available nitrogen(available nutrients).(2)The carbon content of microbial biomass in the biocrust soil gradually increased with the growing season and was consistently higher than that in bare soil at various stages.The biocrusts enhanced enzyme activity at soil depths of 2-5 cm and 10-20 cm,the changes of microbial indices correlated significantly with available phosphorus,available nitrogen,total nitrogen,and available potassium(available nutrients).(3)The microbial biomass carbon in the biocrust soil showed an increasing trend year by year,indicating that the influence of biocrusts on soil microbial biomass carbon was sustainable,but the effect on microbial biomass nitrogen and phosphorus was not significant.In the difference in microbial biomass due to biocrusts between 2021 and 2022,the difference in microbial biomass due to biocrusts in 2021 changed more dramatically.Moreover,the extent of the effect of biocrusts on soil microbial biomass and soil enzyme activity in 2022 is lower than in 2021,probably due to the difference in rainfall which leads to the different extent of the effect of biocrusts on soil microbes.(4)The formation of biocrusts significantly increased the diversity and abundance of soil bacteria and fungi.In the 0-2 cm and 2-5 cm soil layers,biocrusts significantly improved soil bacterial diversity and abundance,with the enhancement effect being more prominent in the 0-2 cm soil layer.These changes correlated significantly with available nitrogen,total phosphorus,available phosphorus,and total potassium(available nutrients).