Interaction Effects Of Temperature And Moisture On Organic Carbon Mineralization In Black Soil

Studying the effects of temperature and moisture changes on organic carbon mineralization in black soil have a great significance in revealing the laws and mechanisms of organic carbon mineralization in black soil under the background of climate change.In this paper,three different organic carbon contents of black soil are taken as the research object.Set four temperatures at-10℃,10℃,20℃,30℃and six water contents,namely 5%,11%,17%,23%,29%,and 50%respectively.Through280 days of in-lab culture test,to study the effects of different temperature and moisture interactions on soil total organic carbon,active organic carbon and soil aggregate composition and aggregate organic carbon distribution.Differentiation of mineralization of black soil with different organic carbon contents under the same temperature and moisture conditions.The results show:（1）The total organic carbon content in the three black soils tested declined.In the condition of water content 5⁵0%,the contents of light and heavy fraction and total organic carbon decreased with the increase of temperature in three black soils,showing the regularity of 30℃<20℃<10℃<-10℃.In the temperature range of-10℃³0℃,high and medium organic carbon content soils had a turning point at a water content of 29%,and low organic carbon content soil at water content of 23%,the contents of total organic carbon of light and heavy fraction,total organic carbon content in the three black soils showed a trend of decreasing first and then increasing.The lowest values of total organic carbon in the three soils were 21.23g·kg^-1,18 g·kg^-1and 15.11 g·kg^-1,they decreased by 3.54 g·kg^-1、2.73 g·kg^-1、2.01 g·kg^-1 respectively,compared with before culture.The lowest values of organic carbon content in the light fraction were 2.67g·kg^-1,1.94g·kg^-1,1.46 g·kg^-1.The lowest values of organic carbon content of heavy fraction were 18.56 g·kg^-1、16.06 g·kg^-1、13.65 g·kg^-1.The mineralization law of light and heavy fraction organic carbon is consistent with that of total organic carbon.In mineralized total organic carbon,the highest mineralization rate of the light fraction were 8.2%、8.12%and 6.60%,they are higher than high fraction’s 6.09%,4.73%and 4.72%in the black soil with high,middle and low organic carbon contents.The organic carbon,light and heavy fraction organic carbon mineralization rates in high organic carbon soils were higher than those in low organic carbon soils.The response of high organic carbon soil to temperature and water changes was more sensitive to low organic carbon content soil.Organic carbon of light fraction was more susceptible to mineralization due to temperature and moisture than heavy fraction.（2）After simulating culture with different temperature and moisture in-lab,the contents of soil microbial biomass carbon,soluble organic carbon,and easily oxidizable organic carbon in black soils with high,medium and low organic carbon contents soils were all reduced.The higher the temperature,the lower the content of soil microbial biomass carbon,soluble organic carbon and easily oxidizable organic carbon,Shows the variation of 30℃<20℃<10℃<-10℃.Between 5%and 50%of water content,Soil microbial biomass carbon,soluble organic carbon,and easily oxidizable organic carbon content did not change significantly at-10°C,however,the soil microbial biomass carbon,soluble organic carbon and easily oxidizable organic carbon content curve at the soil temperature of 10°C,20℃and 30℃showed the trend of decreasing first and then increasing after taking the optimum moisture content as the turning point respectively.In the three black soils with high,medium and low organic carbon content,The highest amount of mineralized carbon in the microbial biomass is 312.99mg·kg^-1,214.82mg·kg^-1 and 177.63 mg·kg^-1,the maximum mineralization rate is 37.57%,28.32%and 24.93%.The highest mineralization of soluble organic carbon is18.7 mg·kg^-1,6.42 mg·kg^-1,8.4 mg·kg^-1,and the maximum mineralization rate was 37.57%,28.32%and 24.93%The maximum mineralization of easily oxidized organic carbon was 3.43 mg·kg^-1,2.23mg·kg^-1 and 1.82 mg·kg^-1and the maximum mineralization rate was 39.39%,35.32%and 34.83%。.（3）After 280 days of cultivating three black soils under different temperature and moisture conditions,the>0.25 mm large aggregates all have the tendency to transform to<0.25 mm microaggregates.After cultivation,the organic carbon content in soil micro-agglomerates（<0.25 mm）changed little,and the organic carbon content in large aggregates（>0.25 mm）decreased significantly.The change rule was consistent with the change of total organic carbon in the soil.At four temperatures（-10°C℃,10℃,20℃and 30℃）,High and medium organic carbon content in black soil is best at 29%water content.Large aggregates have low organic carbon content.