Effects Of Litter Decomposition On Soil Organic Carbon In Vegetation Restoration Of Ziwuling

The dynamic change of soil organic carbon(SOC)reservoir was an important basis to measure the ecological effect of vegetation restoration.However,there were still some unclear mechanisms about the impact of litter decomposition on SOC accumulation in the process of vegetation restoration.This study took five restoration stages of farmland,grassland,Hippohae rhamnoides,Populus davidiana,Quercus liaotungensis in Ziwuling forest area of the Loess Plateau as research objects,combining field survey sampling and indoor analysis methods to study the dynamics of SOC pools and their composition,clarify the characteristics of litter decomposition,further to reveal the accumulation of SOC pools and its driving mechanism of litter during vegetation restoration.It provided scientific basis for soil carbon sequestration management following vegetation restoration on the Loess Plateau.The study's major advances were as follows:(1)Vegetation restoration increased SOC content,soil microbial biomass carbon(MBC)content and soil respiration rate.Compared with farmland,SOC,MBC contents and soil respiration rate were increased following vegetation restoration from grassland to Q.liaotungensis.In each recovery stage,SOC content increased at the initial stage of litter decomposition,but did not change significantly with the increase of decomposition time.While the content of soil soluble organic carbon(DOC)with the increase of decomposition time showed a trend of increasing first and then gradually stabilizing.Soil respiration rate showed a trend of increasing first and then decreasing.The MBC content was consistent with the dynamic change of soil respiration rate,which was shown as farmland < grassland < H.rhamnoides < P.davidiana < Q.liaotungensis.Overall,vegetation restoration increased SOC,MBC and soil respiration rate.The content of DOC decreased with the increase of soil water content in all restoration stages,while the content of MBC and soil respiration rate increased slightly with the increase of soil water content.(2)The decomposition rate of litters showed a downward trend with vegetation recovery.And the content of cellulose and lignin,as well as soil enzyme activity were the main factors affecting the decomposition of litters.In different vegetation restoration stages,the decomposition rates of litter were grassland > H.rhamnoides > P.davidiana > Q.liaotungensis,which increased with soil water.Cellulose content,lignin content,lignin: litters organic carbon(LC)and lignin: litters total nitrogen(LN)were closely related to litters decomposition.They were the main indicators to affect litter decomposition.In addition,soil enzyme activity was significantly correlated with the cellulose and lignin contents of litters.The results showed that ?-1,4-glucosidase(BG)and Cellobiohydrolase enzyme(CBH)that significantly affected the decomposition rate of litters,exhibited a trend of increasing first and then stabilizing with the decomposition rate.Therefore,litter decomposition was mainly restricted by the quality of litters and the extracellular enzyme activity of soil microorganisms.(3)LC,LC: LN was the main factor affecting SOC,DOC,MBC and soil respiration rate at different vegetation restoration stages.In the early stage of vegetation restoration(grassland and H.rhamnoides),SOC,DOC,MBC content and soil respiration rate were significantly correlated with cellulose,lignin and LC: LN of litter.And in the later stage of vegetation restoration(P.davidiana and Q.liaotungensis),DOC,MBC and soil respiration rate were significantly correlated with LN and LC: LN of litters.The quality of litter was the main factor affecting SOC,DOC,MBC and soil respiration rate in different vegetation restoration stages.In summary,vegetation restoration can increase SOC,DOC and MBC pools.Moreover,the decomposition rate of litters decreased with the vegetation restoration.Litters decomposition was significant related to SOC pool and its components,which determined the dynamics of SOC.In detail,the SOC and its components were mainly related to the cellulose and lignin contents of litter in the early stage of vegetation restoration,while they were more closely related to the LN and LC: LN of litters in the later stage of vegetation restoration.Therefore,reasonable management measures can promote vegetation restoration,enhance soil carbon pool function and improve soil nutrient supply capacity,and further to achieve sustainable development of ecosystems.