Soil Respiration Characteristics And Microbial Diversity Of Eroded Slopes On The Hilly Loess Plateau

Understanding soil microbial community and its respiration characteristics on eroded slopes is the key to explore the carbon cycle and carbon emission source and sink effect under erosion condition,and it is of great significance to reveal the microbial mechanism of soil carbon emission induced by erosion.Based on the long-term field observation experiment,soil water and heat and soil respiration monitoring,BIOLOG eco panel and high-throughput gene sequencing technology were used to study the water and heat conditions,soil respiration characteristics,microbial community diversity and microbial composition diversity characteristics on the eroded slopes under different organic carbon background on the hilly Loess Plateau.The main conclusions are as follows:(1)The water and heat conditions of different parts of the slopes changed significantly due to erosion,which led to the change of soil respiration rate.The effect of erosion on soil water and heat conditions and soil respiration is related to soil organic carbon background.The soil water content in the surface layer(0-10 cm)was in the order of deposition area > control area > erosion area.The surface soil temperature(0-10cm)was higher in erosion area and control area,but lower in sediment.The spatial and temporal heterogeneity of soil respiration on the eroded slope was as follows: deposition area > control area > erosion area.(2)There was no significant difference in soil microbial community diversity among different erosion sites,and the effect of erosion on microbial community functional diversity was mainly manifested in the difference of microbial activity determined by organic carbon level.Soil microbial activity,species richness and community function were significantly affected by organic carbon level.Soil microbial activity,species richness and carbon source utilization capacity of three parts at high carbon level were significantly higher than those at low carbon level.The Shannon index,richness index and Mc Intosh index of microbial communities in the three sites under high carbon level were significantly higher than those at low carbon level,but there was no significant difference in soil microbial community diversity index among different erosion sites.From the analysis of different erosion sites,the microbial activity in the sediment area is higher than that in the erosion area,which indicates that the impact of erosion on the functional diversity of microbial community is mainly reflected in the difference of microbial activity determined by the level of organic carbon.Among the six carbon sources of alcohols,amines,amino acids,esters,sugars and acids,the utilization rates of amino acids and esters were the highest,while the utilization rates of alcohols and amines were low.In the plots with lower carbon level,microbial carbon source utilization capacity of sediment area was significantly higher than that of erosion area,but there was no significant difference between sediment area and erosion area at high carbon level.(3)Slope erosion can change the species diversity of soil microorganisms in different parts of the slope,and the degree of change is related to the initial soil organic carbon content.According to Simpson and Shannon index,the species diversity of bacteria and fungi communities in different parts of eroded slopes was high,and the proportion of bacterial communities was uniform.The evenness of fungal community species in erosion and deposition areas with medium organic carbon level and deposition area with high organic carbon level was slightly lower than that of other treatments.In the plots with lower level of organic carbon,erosion reduced the diversity of soil bacteria and fungi,but the impact on the sediment area was small;at the plots with medium and high levels of organic carbon,erosion increased the diversity of soil bacteria and fungi in the sediment area,and had little impact on the erosion area.