Turnover Time And Influencing Factors Of Soil Organic Carbon Components In Different Vegetation Micro-patches In Alpine Meadow

The terrestrial ecosystem carbon cycle model is the most common method to study soil organic carbon dynamics.However,key parameters such as the turnover time of various soil carbon pools have not been accurately quantified,there is still huge uncertainty in the study of soil carbon dynamics.Alpine meadows on the Tibet Plateau have been degraded due to climate change and unreasonable human activities,leading to micro-patches of alpine meadows,which will inevitably affect the turnover of soil organic carbon.However,the research on the turnover time of soil organic carbon components in different vegetation micro-patches has not been studied yet.We apply data assimilation methods to analyze the soil organic carbon mineralization of different vegetation micro-patches in alpine meadows,study the turnover time of various components of soil carbon in different vegetation micro-patches.We also analyze vegetation characteristics,soil physical and chemical properties,and microbial characteristics,which can clarify the influencing factors and mechanisms of the turnover time of each component of soil organic carbon.The results of the study are helpful for in-depth understanding of soil organic carbon turnover after alpine meadow degradation,and provide scientific basis for accurately estimating the carbon dynamics of alpine meadows on the Tibetan Plateau.The main results are as follows:(1)The total biomass of native vegetation,Polygonum viviparum and Ligularia virgaurea micro-patches were not significantly different,and they were all significantly lower than those of Potentilla fruticosa micro-patches.The root lignin content of Polygonum viviparum and native vegetation micro-patches was significantly highest,followed by Potentilla fruticosa and Ligularia virgaurea,and bare ground micro-patches had the lowest.(2)The soil water content,clay and silt content of native vegetation,Potentilla fruticosa and Polygonum viviparum micro-patches were significantly higher than those of Ligularia virgaurea and bare land micro-patches.With the exception of the Potentilla fruticosa patch,soil organic carbon,total nitrogen and C:N decreased to varying degrees after the native vegetation was changed.After the change of native vegetation,the content of large aggregates and the stability of aggregates are reduced,but only bare land patches are significantly reduced;the organic carbon content and C:N change trends of aggregates of different sizes are basically represented by native vegetation,Polygonum viviparum and Potentilla fruticosa>Polygonum viviparum and bare land.Large aggregates(0.25 mm-2mm)are dominant under different vegetation micro-patches,and the content of large aggregates is mainly affected by vegetation biomass,clay content and organic carbon.(3)The changes of soil microbial biomass carbon and nitrogen,?-1,4-glucosidase(BG),leucine aminopeptidase(LAP)and alkaline phosphatase(AP)activities under different vegetation micro-patches were inconsistent.In general,the Potentilla fruticosa patch was the highest and the bare land patch was the lowest.The soil microbial biomass C:N and microbial quotient were the highest in Ligularia virgaurea micro-patches,and the native vegetation patches were the lowest.(4)After 359 days of mineralization cultivation,the cumulative mineralization of soil organic carbon under different vegetation micro-patches ranged from 68.18 g kg^-1SOC to 152.49 g kg^-1SOC,and the soil organic carbon loss of Ligularia virgaurea and bare land micro-patches The highest,the micro-patches of Polygonum viviparum were the second,and the lowest of the micro-patches of native vegetation and Potentilla fruticosa vegetation.Data assimilation analysis shows that the soil active carbon pool ratio,active and slow carbon pool turnover time can be well estimated.The native vegetation active carbon pool and the slow carbon pool have the longest turnover time(78 days and 23.4 years),the Potentilla fruticosa patch has the shortest active carbon pool turnover time(58 days),and the bare land patch has the shortest slow carbon pool turnover time(5.1 years).(5)According to the results of structural equation analysis,the model can explain46%and 85%of the changes in active and slow organic carbon turnover time,respectively.The turnover time of active carbon pool is mainly affected by total biomass and microbial quotient,while the turnover time of slow carbon pool is mainly affected by clay content,microbial quotient and pH.