喀斯特区黄壤与石灰土退耕地土壤有机碳变化特征OA

This study investigates the variation characteristics of Soil Organic Carbon(SOC)content and SOC in different aggregate fractions across various vegetation restoration stages in abandoned croplands,providing a theoretical basis for ecological restoration.Focusing on five succession stages(cropland,grassland,shrubland,forestland,and natural forestland)in yellow soil and limestone soil of the karst area in Guizhou,we analyzed the characteristics of SOC changes at the 0-30cm soil layer and in aggregates of different particle sizes across the five stages. The results showed that SOC significantly increased(P＜0.05)from grassland to forestland in both soil types.At all succession stages,limestone soil exhibited higher SOC than yellow soil,with the highest SOC observed in the 0-10 cm layer of forestland(85.50 g·kg-1 in limestone soil vs.49.95 g·kg-1 in yellow soil).In later succession stages,the SOC growth rate of forestland compared to that of the cropland was significantly higher in limestone soil(48.48％)than in yellow soil(0.24％).Grassland SOC was significantly lower than cropland SOC in both soil types(P＜0.05).With progressive succession,SOC content in different aggregate fractions increased to varying degrees,consistently higher in limestone soil than in yellow soil.Across all vegetation types,large aggregates(＞2 mm)contained higher SOC than smaller fractions.The＞2 mm aggregate fraction contributed the most to SOC storage(34.74％in yellow soil,53.02％in limestone soil).Correlation analysis revealed that in yellow soil,SOC was significantly positively correlated with exchangeable calcium(Ca),total nitrogen(N),and total potassium(K)(P＜0.01),and negatively correlated with bulk density(P＜0.05).In limestone soil,SOC showed strong positive correlations with exchangeable Ca,magnesium(Mg),TN,total phosphorus(P),and sand content(P＜0.01),while negatively correlating with bulk density,silt,and clay(P＜0.05).Principal Component Analysis(PCA)indicated clear differentiation among grassland,shrubland,and cropland in yellow soil,whereas limestone soil exhibited less distinct separation among the three abandoned vegetation types and cropland.Overall,returing farmland to vegetation helps improve soil quality,alleviates soil compaction,and enhances soil organic carbon storage.Limestone soil demonstrates greaterr carbon sequestration benefits compared to yellow soil.