坡度和坡位对紫色土有机碳形态变化及团聚体组成的影响OA

In this study,a typical tobacco-growing area in Huidong County of Liangshan Prefecture was selected,and soil total organic carbon(TOC),dissolved organic carbon(DOC),readily oxidizable organic carbon(ROC),particulate organic carbon(POC),mean weight diameter(MWD)of aggregates,and the percentage of>0.25 mm aggregates(R0.25)were analyzed,in order to investigate the effects of slope gradient(<5°,5°-10°,10°-15°,15°-20°)and slope position(upper,middle,lower)on soil aggregate composition,stability,organic carbon fractions,and their interrelationships.The results showed that as slope gradient increased,average TOC content gradually decreased.Compared to slopes of 0-5°,TOC content significantly decreased by 18.43%,23.09%and 37.24%for slopes of 5°-10°,10°-15° and 15°-20°,respectively.Average POC content showed that slopes of 0-5°>5°-10°>15°-20°.With increasing slope gradient,the content of>2 mm water-stable aggregates decreased,along with R0.25 and MWD,indicating reduced soil structural stability.As slope position ascended,R0.25 and MWD decreased,with the highest MWD observed at the lower position with slopes of 0-5°,indicating that greater aggregate stability in these areas.Aggregates of 0.5-1 mm and 0.25-0.5 mm were the primary factors influencing changes in soil DOC and ROC.In conclusion,as slope gradient increased,soil organic carbon content decreased,and aggregate stability declined,whereas slope position had no significant impact on soil organic carbon pool.