Temperature Sensitivity And Driving Factors Analysis Of Soil Organic Carbon Decomposition Across Chinese Typical Cropland

Cropland ecosystems are artificially built with crop yield as the core ecosystem,and are also the main source of greenhouse gas emissions.Soil carbon emissions from Cropland can account for 21%-25%of anthropogenic greenhouse gas emissions,which is important for the global carbon cycle and balance.Soil respiration is a key process of the soil carbon cycle,and its temperature sensitivity(Q₁₀)can describe the response of soil respiration to temperature rise,and is one of the important evaluation indicators of global warming and soil carbon cycle feedback.Studying the Q₁₀ and driving factors of soil organic carbon decomposition in Cropland ecosystems in China is of great research for accurately assessing the response of China's Cropland carbon cycle process to global climate change.Therefore,this study uses five Chinese long-term fertilization networks in Heilongjiang Hailun?HL?,Shanxi Shouyang?SY?,Jiangxi Nanchang?NC?,Hunan Qiyang?QY?and Fujian Baisha?BS?as the research area,and using indoor continuous temperature change cultivation and continuous measurement techniques to explore the effects of fertilization on soil respiration and Q₁₀0 and the driving factors that affect Q₁₀ on a regional scale.This study provides parameters for predicting the response of Cropland ecosystems to future climate change,and at the same time provides new ideas and perspectives for understanding of the CO₂ flux change mechanism in the region.It has important theoretical guiding significance for the development of Cropland soil management and climate change response.The main results of the study are as follows:1.Long-term application of chemical fertilizers?NPK?can significantly affect soil respiration rate,and the temperature sensitivity of soil organic carbon decomposition?P<0.05?.NPK decrease the soil respiration rate,but increases Q₁₀;compared with no fertilizer?Control?,the soil respiration rate of NPK was reduced by 5.26%(44.00?g g^-1 d^-1 vs.42.10?g g^-1 d^-1);in contrast to the decrease in soil respiration rate by NPK,the Q₁₀ of NPK increased by 17.89%?1.23 vs.1.45?.2.NPK significantly affects the biochemical properties of the soil?P<0.05?.NPK can significantly affects soil microbial biomass carbon?MBC?,?-cellobiosidase?CBH?,N-Acetyl-glucosidase?NAG?,total nitrogen?TN?,soil organic carbon?SOC?,and dissolved organic carbon?DOC?,dissolved organic nitrogen?DON?,nitrate nitrogen?NO₃^--N?and ammonium nitrogen?NH₄⁺-N?,the increase rate were22.43%,2.19%,80.82%,13.73%,11.96%,22.07%,67.00%,86.67 and 44.94%,respectively;and it can significantly decrease of microbial biomass nitrogen?MBN?and pH by 19.80%and 8.94%,respectively.3.In Control soil,Q₁₀ was significantly positively correlated with pH and MBC?P<0.05?;in NPK,Q₁₀ was significantly positively correlated with pH,DON,NO₃^--N and SOC?P<0.05?;and it has a significant negative correlation with NAG,DOC and NH₄⁺-N?P<0.05?.In Control soil,pH is the most important factor affecting Q₁₀ variation;while on NPK,NH₄⁺-N is the most important factor affecting Q₁₀variation.And compared to Control,NPK can affect pH and NAG and indirectly affect Q₁₀0 by changing the content of NH₄⁺-N.4.On a regional scale,the Q₁₀ ranges between 0.89 and 2.15,with an average value of 1.47 and a median value of 1.43.The order of Q₁₀ is:SY?1.49?>NC?1.38?>BS?1.22?,QY?1.17?,HL?1.14?.There is no significant difference in Q₁₀ between BS,QY and HL.5.The Q₁₀0 has spatial heterogeneity in Cropland.Q₁₀ and SOC,DON,pH,Sand,NH₄⁺-N,Long,NAG,Clay,Silt,mean annual average temperature?MAT?and mean annual average precipitation?MAP?have significant correlations?P<0.05?;climate factors,incubation time,sites,soil factors and experimental treatments explain the changes in Q₁₀ by 0.82%,0.62%,5.49%,91.63%and 1.44%,respectively;among them,soil factors are the most important factor affecting the variation of Cropland Q₁₀,and DON is the driving factor affecting the variation of Cropland Q₁₀.In summary,fertilization can significantly affect the temperature sensitivity of soil organic carbon decomposition in Chinese Cropland,and there is show spatial heterogeneity in the temperature sensitivity of organic carbon decomposition;on Control and NPK soils,the main controlling factors of Q₁₀0 variation are pH and NH₄⁺-N,respectively.And compared to Control,NPK can affect pH and NAG and indirectly affect Q₁₀ by changing the content of NH₄⁺-N;analysis of multiple factors,soil factors are the most important factor affecting the variation of Cropland Q₁₀ on a regional scale.Therefore,under the conditions of climate change,the impact of agricultural fertilization measures on the carbon balance of terrestrial ecosystems and atmospheric CO₂ concentration changes should not be ignored;and the effects of fertilization measures and differences in locations and soils should also be fully considered in the terrestrial ecosystem and climate system model,so as to accurately estimate the terrestrial soil carbon source and sink capacity and its extent under climate change conditions.