两种凋落叶添加对马尾松土壤酶活性及细菌群落结构的影响

Impact of Different Litter Addition on Enzyme Activities and Bacterial Community Composition of Soils from Pinus massoniana Plantations

中国亚热带典型针叶树种马尾松的凋落叶碳磷元素含量之比(C∶P)较高,但其林下土壤的微生物生物量碳磷之比(MBC∶MBP)却较低。为了解马尾松人工林土壤微生物吸收同化底物的过程,将针叶树种马尾松凋落叶(C∶P高)和阔叶树种马褂木凋落叶(C∶P低)分别加入马尾松的林下土壤中(0~10 cm),进行为期60天的室内培养试验。结果显示,添加马褂木凋落叶的土壤MBC、β-葡萄糖苷酶(βG)和纤维素水解酶(CBH)显著高于添加马尾松凋落叶的土壤;两种处理间的酸性磷酸单酯酶(ACP)活性有显著差异,但其酶效率(ACP∶MBC)无显著差异;冗余分析表明ACP∶MBC与AvaiP∶MBC(单位质量的微生物所拥有的有效磷数量)之间呈正相关关系,MBC∶MBP与AvaiP∶MBP之间也呈正相关关系;细菌16S rRNA测序显示培养60天后添加马褂木凋落叶的土壤细菌群落中嗜营养的变形菌为优势类群,而添加马尾松凋落叶的土壤贫营养的酸杆菌为优势类群。结果表明,易利用碳的数量是决定土壤MBC含量的重要因素,ACP活性与微生物生物量密切相关,微生物分泌ACP除了获取磷元素,也与辅助获取碳元素有关。

Although the leaf litter of Pinus massoniana is associated with relatively high C∶P,soils from the Pinus massoniana plantations show relatively low MBC∶MBP.To get a deeper insight into the process of soil microorganisms of the plantations assimilating substrates,this study examined the dynamics of soil available nutrients,MBC,MBP and enzyme activities over a 60 day laboratory incubation by adding leaf litters of Pinus massoniana(PM,higher C∶P)and Liriodendron Chinese(LC,lower C∶P)separately(i.e.two treatments)to soils from young Pinus massoniana plantations(0~10 cm).Soils amended with LC showed significantly higher MBC contents and higherβG and CBH activities than soils amended with PM.The activity of ACP was significantly different between the two treatments,whereas ACP efficiency was similar.Redundancy analysis showed positive correlation between ACP∶MBC and AvaiP∶MBC(available phosphorus per unit of MBC),as well as positive correlation between MBC∶MBP and AvaiP∶MBP.The analysis of high-throughput sequencing of bacterial 16S rRNA after incubation revealed that the copiotrophic Proteobacteria were dominant organisms in LC-addition soil,while the oligotrophic Acidobacteria were the dominant organisms in PM-addition soil.The results suggested that the quantity of labile carbon in leaf litters was the key determinant of MBC,and ACP activity was strongly dependent on MBC.It seemed that microorganisms released ACP not only to meet their demand for phosphorus,but also to facilitate carbon acquisition.