高寒草甸土壤有机碳活性组分对灌丛化的响应

Response of Soil Organic Carbon Active Components to Shrub Encroachment in Alpine Meadows

[目的]草地灌丛化过程的植被群落演替会影响土壤有机碳库,而土壤有机碳(SOC)活性组分能够敏捷反映土壤有机碳库变化。分析灌丛化对高寒草甸SOC活性组分的影响,为全球气候变化背景下青藏高原草地土壤有机碳库变化和固碳研究提供数据支撑。[方法]以青藏高原川西锦鸡儿(Caragana erinacea)灌丛草甸为研究对象,分析不同灌丛化阶段(未灌丛化、中度灌丛化和重度灌丛化草甸)0—10,10—20,20—40 cm土壤理化性质、碳转化酶活性和SOC活性组分特征。[结果](1)灌丛化使得0—20 cm土壤含水量(SWC)显著减小,各土层SOC含量均在重度灌丛化草甸最大,中度灌丛化草甸土壤pH值显著增大。(2)中度灌丛化草甸土壤淀粉酶活性(SAA)显著低于未灌丛化草甸,10—40 cm土壤蔗糖酶活性(SSA)也显著较低,SSA在重度灌丛化阶段显著强于未灌丛化草甸。(3)与未灌丛化草甸相比,中度灌丛化草甸0—10,10—20,20—40 cm易氧化有机碳(ROOC)含量分别显著减少16.79%,21.73%和31.11%,0—10 cm土壤可溶性有机碳(DOC)和微生物生物量碳(MBC)含量也显著减少;重度灌丛化草甸0—10 cm土壤颗粒态有机碳(POC)和ROOC含量分别增大24.37%和29.54%,10—20 cm土壤MBC和DOC分别增大12.96%和10.38%,20—40 cm土壤MBC和DOC分别增大57.62%和22.10%。(4)土壤有机碳活性组分均与TN,SWC,SOC以及碳转化酶活性显著正相关,ROOC与pH值显著负相关。[结论]研究区域川西锦鸡儿灌丛化初期土壤有机碳活性组分含量降低,而灌丛化后期土壤有机碳及其各活性组分均得到积累,可能对该区域土壤有机碳积累和土壤质量提升产生积极效应。

[Objective]The succession of vegetation communities in the process of grassland encroachment by shrubs affects the soil organic carbon(SOC)pool,and these changes are quickly reflected by the active components of SOC.The effect of shrub encroachment on the active components of SOC in an alpine meadow was analysed to provide data support for the study of changes in the SOC pool and carbon sequestration in grasslands of the Qinghai-Xizang Plateau against the backdrop of global climate change.[Methods]Taking the Caragana erinacea shrub meadow in the Qinghai-Xizang Plateau as the research target,changes in the soil physical and chemical properties,carbon cycle enzyme activities,and SOC active components in the 0—10,10—20 cm,and 20—40 cm soil layers at different shrub encroachment stages(non-shrub,moderate-shrub,and heavy-shrub meadow)were analysed.[Results](1)The soil water content(SWC)in the 0—20 cm layer decreased significantly by shrublading.Moreover,the SOC content in all soil layers was the highest in the heavy-shrub meadow.Additionally,the soil pH value increased significantly in the moderate-shrub meadow.(2)The soil amylase activity(SAA)in the moderate-shrub meadow was significantly lower than that in the non-shrub meadow,and the soil sucrase activity(SSA)in the 10—40 cm soil layer was also significantly lower.SSA in the heavy-shrub meadow was significantly higher than that in the non-shrub meadow.(3)The readily oxidizable organic carbon(ROOC)contents in the 0—10,10—20 cm,and 20—40 cm layers in the moderate-shrub meadow were 16.79%,21.73%,and 31.11%lower than those in the non-shrub meadow,respectively.The dissolved organic carbon(DOC)and microbial biomass carbon(MBC)contents in the 0—10 cm layer also decreased significantly.The particulate organic carbon(POC)and ROOC contents in the 0—10 cm layer were 24.37%and 29.54%higher than those in the non-shrub meadow,respectively.The MBC and DOC contents in the 10—20 cm layer were 12.96%and 10.38%higher than those in the non-shrub meadow,respectively.The MBC and DOC contents in the 20—40 cm layer were 57.62%and 22.10%higher than those in the non-shrub meadow,respectively.(4)SOC active components were significantly positively correlated with TN,SWC,SOC,and carbon cycle enzyme activity,and ROOC was strongly negatively correlated with pH value.[Conclusion]The content of SOC active components decreased during the early stage of C.erinacea shrub encroachment in the study area,whereas SOC and its active components underwent accumulation during the later stage of shrub encroachment.This may have a positive effect on the accumulation of SOC and the improvement of soil quality in this area.