滇中元江栲林下土壤活性有机碳空间分布特征

Spatial distribution characteristics of soil active organic carbon of Castanopsis orthacantha forest in Central Yunnan Plateau

为探究滇中元江栲林下土壤活性有机碳在垂直空间上的分布及其影响机制,以滇中地区不同海拔(2090~2490 m)、不同坡向(阴、阳坡)元江栲林为研究对象,探究林下0~60 cm土层土壤有机碳(SOC)、微生物量碳(MBC)、可溶性有机碳(DOC)、易氧化有机碳(ROC)、颗粒性有机碳(POC)含量的空间分布特征。结果表明:SOC、MBC、ROC、POC含量随海拔上升先升高再降低,DOC含量随海拔上升逐渐降低,4种活性有机碳组分含量表现为POC>ROC>MBC>DOC。4种土壤活性有机碳含量均阴坡高于阳坡,且随土层深度增加呈明显下降趋势,0~20 cm土层高于20~40、40~60 cm土层。各个土壤活性有机碳组分在土壤有机碳中的占比表现为POC/SOC>ROC/SOC>MBC/SOC>DOC/SOC,POC为4种活性有机碳库中的主要碳库,MBC/SOC比值随海拔上升无明显变化规律,ROC/SOC、POC/SOC比值随海拔上升先增大再减小。SOC、MBC、ROC、POC含量任意两者间均呈极显著正相关(P<0.01),土壤活性有机碳含量与土壤pH值呈极显著负相关(P<0.01)。海拔与土层极显著影响SOC、DOC、MBC、ROC、POC含量(P<0.001),坡向极显著影响SOC、POC含量(P<0.01,P<0.001),显著影响DOC含量(P<0.05)。

In order to investigate the vertical distribution characteristics of soil organic carbon and its influence mechanism in Castanopsis orthacantha evergreen broad-leaved forest in Central Yunnan Plateau,we selected Castanopsis orthacantha forest at different altitudes(2090-2490 m)and different slope directions as objective to investigate the spatial distribution characteristics of organic carbon(SOC),microbial biomass carbon(MBC),soluble organic carbon(DOC),easily oxidized organic carbon(ROC),and granular organic carbon(POC)at 0-60 cm depths of soil.The results revealed:the contents of SOC,MBC,ROC,and POC initially increased and then decreased with increase of elevation,and the content of DOC decreased gradually with increase of elevation;the contents variation of the four active organic carbon fractions were followed as POC>ROC>MBC>DOC.The contents of soil organic carbon and active fractions were higher on the shady slope compared to the sunny slope,and decreased with soil depth significantly,the contents in 0-20 cm depth were higher obviously than that in 20-40 cm and 40-60 cm depth.The proportion of each soil active organic carbon component in soil organic carbon was POC/SOC>ROC/SOC>MBC/SOC>DOC/SOC,the particulate organic carbon(POC)was the main carbon pool among the four active carbon pools.The ratios of MBC/SOC have no significant variation with increase of elevation,while the ratios of ROC/SOC and POC/SOC finitially increased and then decreased.The contents of SOC,MBC,ROC and POC were positively correlated with each other,labile organic carbon was significantly negatively correlated with pH of soil.Altitude and soil depth have extremely significant impact on SOC,DOC,MBC,ROC and POC content.Slope direction highly significant effect on SOC,POC content and significantly affects DOC content.