The Dynamics Of Soil Organic Carbon Fractions In Different Vegetation Types Of Tianshan Forest

As a huge carbon storage,soil organic carbon(SOC)is affected by temperature,moisture,vegetation type and human disturbance,and its content also changes.Tianshan forest is an important soil carbon pool in arid area of Northwest China,and the content of soil organic carbon is high.The change of vegetation type has a profound influence on the change of the circulation process of the forest material,which has a feedback effect on the vegetation,some of which are sensitive to the temperature and vegetation type,and the bioactive active organic carbon component is in a relatively fast decomposition and transformation process,and it can reflect the environment before the change of the soil carbon pool.The small change of soil is an important way for the active organic matter in the soil carbon pool and the vegetation soil material cycle.Therefore,it is one of the hot topics to study the impact of vegetation type changes on the main functions of forest ecosystems.In this study,the soil organic carbon content and interannual dynamic changes under different vegetation types were systematically studied in the forest soil of Tianshan Mountain.It was helpful to explore the dynamic and dynamic trend of soil organic carbon pool in the Tianshan forest soil and its response to global change,and to evaluate the soil organic carbon in the forest ecosystem.The characteristics of space-time scale are of practical significance.The main conclusions are as follows:(1)The soil organic carbon content in Tianshan forest is relatively high.The average values of soil surface(0-10 cm)SOC,soluble organic carbon(DOC),light component organic carbon(LFOC)and microbial biomass carbon(MBC)in the soil surface of spruce forest were 114.74,3.92,13.54 g/kg and 323.97 mg/kg,respectively,and the average values of soil lower layer(10-20 cm)were 101.43,3.01,11.37 g/kg and 283.13 mg/kg respectively.The average values of the soil surface(0-10 cm)SOC,DOC,LFOC and MBC were 110.04,3.83,12.62 g/kg and 298.17 mg/kg,respectively,and the average values of the lower soil layer(10-20 cm)were 95.46,3.03,10.42 g/kg and 261.84 mg/kg respectively.The average values of SOC,DOC,LFOC and MBC in the soil surface(0-10 cm)were 104.83,3.78,11.58 g/kg and 276.31 mg/kg,and the average values of the lower soil layer(10-20 cm)were 88.65,2.83,9.49 g/kg and 244.70 mg/kg respectively.The contents of SOC,DOC,LFOC and MBC in the surface layer(0-10 cm)and the lower layer(10-20 cm)were different under different vegetation types.The trend of total content is spruce forest > shrub land > grassland.The content of organic carbon in the soil surface is higher than that in the lower layer.(2)the content of the organic carbon components in the surface and lower layer of the spruce forest,shrub land and grass soil in different periods has a certain difference and the trend of the whole dynamic change is roughly the same.That is,from April(thawing period)to the next year February(deep freezing period),the change of SOC content presents a relatively smooth trend,and the content of DOC increases first and then decreases.The content of LFOC decreased slowly and slowly,and the MBC content changed first and then decreased rapidly.The soil DOC/SOC value of spruce forest is fluctuating,the surface and lower layers of soil are 2.90%-3.54% and 3.17%-3.90%,respectively,and the whole soil surface and lower layer are 3.08%-3.64% and 3.29%-4.19,respectively.The surface and subsurface variation ranges are 3.13%-3.91% and 3.54%-4.20% respectively.The LFOC/SOC value of the spruce forest soil was reduced first and then gradually rising,and the soil surface and lower layers were 8.37%-12.12% and8.69%-11.90%,respectively,and the soil surface and the lower layer of soil surface and lower layer were 8.15%-11.08% and 8.49%-12.22% respectively.The overall trend of decline first and then slowly increase,and the variation range of surface and lower layer is 5.92%-10.82% and 5.48%-11.96% respectively.The whole soil microbial entropy(MBC/SOC value)of spruce forest,irrigation land and grassland all showed a trend of rising first and then decreased rapidly.The change range of soil surface and lower layer were 0.17%-0.41%,0.17%-0.38% and0.15%-0.43%,0.16%-0.38% and 0.16%-0.43% respectively.(3)the analysis of synergistic effect showed that soil organic carbon content was significantly affected by the type of vegetation,period,depth of soil layer,theinteraction of vegetation type and period(P<0.01),and the effect of vegetation type was most obvious,and the order of the contribution of various factors to the total body variation of organic carbon content was vegetation type.Type > period > soil >vegetation and period interaction.The influence of other indicators and interactions reached a significant level.Redundancy analysis showed that soil temperature and water content were the most important factors affecting SOC content.Between the components of SOC,SOC and LFOC have positive correlation,and the correlation with DOC and MBC is not obvious;soil LFOC has a negative correlation with DOC and MBC,and the soil DOC and MBC show the opposite trend.Between soil environmental factors and soil environmental factors,both DOC and MBC have positive correlation with temperature,while LFOC and temperature have the opposite trend.DOC and MBC have a negative correlation with water content,and the soil water content is negatively correlated with temperature;the pH values and electrical conductivity of soil are less explained,so the content of SOC components is not with pH value and conductivity.There is a clear correlation.