不同树种混交对团聚体有机碳及其组分的早期影响

Early effects of different tree species mixing on aggregate organic carbon fractions

人工林在固碳增汇中具有重要作用,且不同树种混交对土壤有机碳的影响存在差异。本研究以南亚热带3种典型人工混交林(马尾松(Pinus massoniana)+红锥(Castanopsis hystrix)、马尾松+格木(Erythrophleum fordii)、格木+米老排(Mytilaria laosensis))为对象,从团聚体水平比较了不同树种混交对有机碳及其组分的影响,以及各级团聚体有机碳的驱动因素。结果表明:格木+米老排混交林促进了粗大团聚体的形成,团聚体平均重量直径在该林分中最大(1.71 mm),其次是马尾松+格木混交林(1.39 mm),马尾松+红锥混交林中最低(1.26 mm);粗大团聚体(>2 mm)有机碳含量在格木+米老排混交林中显著增加(P<0.05),分别为马尾松+红锥、马尾松+格木混交林的1.8倍和1.4倍;格木+米老排混交林还促进了团聚体内颗粒有机碳的增加,且增加的这部分碳主要源于粗大团聚体中粗颗粒和细颗粒有机碳,以及细大团聚体中粗颗粒有机碳的增加;格木+米老排混交林通过增加凋落物和根系的输入,促进了团聚体稳定性及团聚体有机碳的积累。

Plantations play an important role in carbon sequestration,with different effects of tree species mixture on soil organic carbon.In this study,we examined the effects of three typical two-species mixed plantations,Pinus massoniana+Castanopsis hystrix(PC),Pinus massoniana+Erythrophleum fordii(PE),and Erythrophleum fordii+Mytilaria laosensis(EL),on aggregate organic carbon and its fractions in the south subtropical area,as well as the driving factors of organic carbon at different aggregate levels.The results showed that EL promoted the formation of large macroaggregates.The highest value of mean weight diameter of aggregates was observed in EL(1.71 mm),followed by PE(1.39 mm)and PC(1.26 mm).The macroaggregate organic carbon content(>2 mm)was 1.8 and 1.4 times higher in EL than those of PC and PE,respectively.EL promoted the accumulation of particulate organic carbon within aggregates,which was mainly originated from coarse and fine organic particulate carbon within large macroaggregates,and coarse particulate organic carbon within small macroaggregates.EL promoted the stability of aggregates and the accumulation of aggregate organic carbon by increasing inputs of leaf litter and roots.