Response Of Organic Carbon Mineralization And Microbial Mechanisms To Leaf Litter And Nitrogen Additions In Subtropical Forest Soils

In forest ecosystems,the litters from plants is one of the main sources of soil organic matter(SOM),The inputting litters can promote the decomposition of soil organic matter.At the same time,the exogenous fresh organic matter provids microorganisms the easily decomposable carbon and energy,which may increase their demanding for nitrogen.The microorganism may decompose SOM to obtain the available nitrogen to growth,which in turn affect the priming effect.In order to explore the internal mechanism of the priming effect,Here,we adopted the method of incubation experiments,to study the effects of three types of ¹³C-labeled litters and nitrogen on the internal mechanism that affects the priming effect of soil organic matter by analyzing changes in the gas emissions,soil basic physical and chemical properties and soil microbial indicators during early and later stages.The main conclusions are as follows:1)The litter addition improved the availability of soil nutrients and carbon substrates,leading a significant positive priming effect in the initial stages,and as the decreasing of nutrients content and the availability of carbon substrate,the organic matter became more complex,the priming effect decreased gradually,but the nitrogen addition had no significant effect on the priming effect.2)In the early stage of decomposition of litter,fungi played a key role in the decomposition of cellulose and lignin.the litter addition may promote the decomposition and utilization of soil easily decomposable organic matter by producing the cellulose hydrolases such as?G and CBH in the early stage of incubation.Subsequently,the soil nutrients and easily decomposable organic matter declined rapidly,the microbial"nutrient mining"enhanced,and the soil PHO enzyme activity was significantly improved.At the same time,the activity of bacteria were significantly improved.The differences in microbial composition may be mainly attributed to Proteobacteria,Basidiomycota,and Mortierellomycota.Nitrogen addition had no significant effect on microbial community structure and enzyme activity.3)The priming effect was influenced by biotic and abiotic factors.The litter addition changed the basic properties of the soil,and the soil carbon availability dominated the decomposition of the organic matter in the early stage,as the content of easily decomposable organic carbon decreased,the microbial"nutrient mining"enhanced.The bacteria was the main factor affecting the priming effect of soil organic carbon in the later incubation period.