Decomposition Rates Of Soil Carbon Pool And Its Influencing Factors In Qinling Taibai Mountain

Forest soil carbon pool is the largest soil carbon pool in the world,which accounts for 40%of the global soil carbon pool.Therefore,a small change in forest soil carbon pool can have a profound influence on atmospheric CO₂concentration and the global carbon budget.With global warming increases,the response of forest soil carbon pools to warming at different elevations has gained more and more attention,which is affected by multiple factors such as microbial biomass,extracellular enzymes,and soil aggregate structure.Taibai Mountain,the main peak of the Qinling Mountains,is a typical representative of Chinese forest ecosystem.It has unique natural geographical conditions,rich biodiversity,and great potential for vegetation carbon sequestration.It provides a natural experimental platform for conducting research on forest soil carbon pool decomposition.In our study,four typical vegetation types with an elevation of 1500 m-2600 m on the northern slope of the Taibai Mountain were used as the research object to study the soil respiration,soil physical and chemical properties,microbial biomass,and extracellular enzyme activity during incubation,clarify the change characteristics of forest soil carbon pool decomposition rate during incubation,and reveal the response of forest soil carbon pool decomposition to warming with elevation and its underlying mechanism.The main research progress and conclusions are as follows:(1)In the bulk soil of forest soils,the proportion of active C-pool to the total carbon pool decreases from 35.0%to 29.2%with increasing elevations,the proportion of slow C-pool to the total carbon pool decreases from 35.0%to 33.1%with increasing elevations,and the proportion of passive C-pool to the total carbon pool increases from 32.5%to 37.7%with increasing elevations.The average Q10 values of soil active,slow,and passive C-pools are1.2,2.8,4.1,respectively.This indicates that warming-induced CO₂emission acceleration was mainly from the slow and passive C-pools rather than active C-pool.Therefore,warming-induced CO₂emission acceleration is more pronounced at high elevation.(2)After the bulk soil of the forest soils at 4 elevations was cultivated at 15?,25?and35?for 336 days,the microbial biomass carbon(MBC)decreased by 84.0%,87.0%,and88.0%;?-glucosidase(BG)decreased by 48.4%,82.1%,92.1%;?-N-acetylglucosaminase(NAG)decreased by 73.9%,88.0%,98.2%;leucine aminopeptidase(LAP)decreased by89.4%,80.6%,89.8%;?-xylosidase(BX)increased by 2.1 times,7.2 times,and 9.3 times.This suggested that warming drives microbial communities to allocate?-1,4-glucosidase(BG)production to?-1,4-xylosidase(BX),?-1,4-N-acetylglucosaminidase(NAG),and leucine aminopeptidase(LAP)production,and the direction and magnitude of such allocation is significantly related to elevation.(3)In the soil aggregates of forest soils,the average proportions of active,slow,and passive carbon pools of micro-aggregates are 19.6%,14.4%,and 66.1%,respectively;the average proportions of meso-aggregates are 25.5%,36.8%,and 37.7%,respectively;the average proportions of macro-aggregates are 25.1%,29.3%,and 45.6%,respectively.This shows that micro-aggregates have good carbon sequestration ability,but are more sensitive to warming,and the CO₂emitted by soil respiration mainly comes from meso-aggregates and macro-aggregates.