Effects Of Exogenous Straw And Temperature On Soil Organic Carbon Mineralization In Karst Area

Soil organic carbon mineralization is a basic biochemical process of terrestrial ecosystem,and the greenhouse gases released by it play an important role in climate warming.Among them,exogenous organic matter and temperature are important factors affecting soil organic carbon mineralization.In this study,typical soil calcareous soil and zonal soil yellow soil in karst area of Guizhou were studied by ¹³C stable isotope combined with indoor simulated culture experiment.the effects of adding ¹³C rice straw(no exogenous ¹³C rice straw and ¹³C rice straw)on soil organic carbon mineralization,organic carbon active components and soil microbial community were studied at different temperatures（15℃,25℃and 35℃）.The main conclusions are as follows:（1）The mineralization rate of soil total organic carbon and original organic carbon reached the maximum on the 1st day,then decreased rapidly（1-30 days）,and then tended to be flat（30-60 days）.After 60 days of culture,¹³C rice straw and temperature significantly promoted the mineralization of soil organic carbon in calcareous soil and yellow soil:the excitation effect of 13C rice straw on the original organic carbon in these soils was 199.95%and 190.96%respectively at 25℃.Compared with 15℃and 35℃,it increased by 26.14%,97.05%,15.40%and 5.85%,respectively.The contribution rate of ¹³C rice straw in soil total organic carbon was3.79%,8.45%and 6.30%at 15℃,25℃and 35℃,and 5.33%,6.03%and 6.13%at15℃,25℃and 35℃.The temperature sensitivity of soil organic carbon mineralization is only affected by soil types,in which the temperature sensitivity coefficient Q10 of soil organic carbon mineralization in lime soil is in the range of1.01～2.90,while that of yellow soil is between 1.02 and 1.61.（2）The range of soil microbial biomass carbon content in lime soil and yellow soil was 56.99～79.67mg/kg and 210.01-271.81 mg/kg,respectively.The content of soluble organic carbon in yellow soil was lower than that in lime soil.The effect of rice straw on the soluble organic carbon of the two kinds of soil was mainly in the early stage,and the effect on calcareous soil was greater than that on yellow soil.The range of soil microbial biomass carbon content in lime soil and yellow soil was 397.19～573.74mg/kg and 76.85～351.574 mg/kg,respectively,and the content of microbial biomass carbon in lime soil was significantly higher than that in yellow soil.The addition of rice straw increased the content of microbial biomass carbon in lime soil and yellow soil.The change of temperature only had an effect on the transformation of rice straw.（3）In calcareous soil and yellow soil,actinomycetes,campylobacter,Proteus,acidobacteria and spore monomonas（thick-walled bacteria）are the dominant bacteria,and the cysts are the dominant fungi.The addition of rice straw increased the diversity of bacterial community and decreased the diversity of fungal community in lime soil,but showed the opposite trend in yellow soil.Soil organic carbon cumulative mineralization and organic carbon content are the key factors driving the change of bacterial and fungal community structure at the gate level.