Effects Of Topsoil Organic Carbon Stability By Heat Stress In Subtropical Forest

Temperature,heavily influenced the activity and efficiency of the creatures living in soils,is one of the critical factors to control soil mineralization,litter decomposition and the stability of soil organic carbon.Therefore,under the circumstance of the frequent occurrence of unprecedented attack of summer heatwave across the world,it is of great significance to explore the stability of soil organic.In this study,the soil was collected from the surface(0-10cm)of Acacia mangium forest in Daling Mountain Forest Park in Dongguan.which is divided and incubated in common temperature(25 oC)in the following three conditions: no stress(control),35 oC stress for 6 hours and 45 oC stress for 6 hours,respectively,setting up,meaningwhile,with added and non-added litter treatment.By measuring the stability index of soil organic carbon,e.g.the mineralization rate of organic carbon,microbial biomass organic carbon,dissolved organic carbon,hot water extractable organic carbon,particulate organic carbon,mineral associated organic carbon,chemical stable organic carbon and total organic carbon during the incubation,it was studied that how the heat sterss can effect on the stability of soil organic carbon in forest soil and the decomposition of the litter from the soil.The results showed that,the heat stress significantly contributed the mineralization rate of soil organic soil organic carbon(p<0.05)in the topsoil of subtropical forest during the early incubation,shrinked the proportion of the SMBC,DOC,HWOC in SOC,resulting in a stability decline in soil activated organic carbon stock(p<0.05).It is noticeable that the higher the stress,the higher the stability it is.However,there was no significant effect on the SOC and pH value(P> 0.05)with the heat stress in the short-time incubation.Moreover,the heat stress also facilitated the decomposition of the litter from surface soil of subtropical forest(p<0.05),where it was verified that the CO2 releasing rate was heavily correlated to SOC and POC(p<0.05).The litter soil SOC was related to POC,m-SOC and CSOC,but,with a prolonged incubation time,the litter only response to the POC but the mineralization rate of organic carbon decreased and gradually reached to stability.The heat stress had been verified to have no influence on the interaction between litter decomposition and composition of organic carbon(p> 0.05),and during this interaction,the soil organic carbon fractions had a significant effect on SOC(p<0.01).The results in this study indicated that,short-term heat stress showed no significant effect on the inert organic carbon pool in the subtropical forest,but a certain loss of the active organic carbon pool.In the condition of heat stress,it was obvious that the litter decomposition contributed to accumulation of organic carbon by adding litter,which therefore did not show significantly effects on the stability of soil organic carbon in the subtropical forest in short term.