川西亚高山三种天然次生林土壤微生物多样性变化特征

Diversity of topsoil microbial community in three natural secondary forests in subalpine regions of Sichuan,China

开展川西亚高山相似土壤母质背景下天然次生林土壤微生物群落结构及其多样性探究,可加深次生林更新过程中土壤微生物群落结构变化的认知。选取川西米亚罗林区20世纪60年代采伐后经自然更新恢复形成的3种天然次生林(槭-桦阔叶林,ABB;桦-槭-冷杉针阔混交林,BAA;岷江冷杉林,AFF),分析林下表层(0—20 cm)土壤微生物群落结构变化及其影响因素,结果显示:(1)3种林型土壤细菌Chao1和Shannon指数均极显著高于真菌,但仅真菌群落的Shannon指数差异显著,表现为BAA>ABB>AFF;(2)细菌群落优势门主要为变形杆菌门、酸杆菌门、疣微菌门、拟杆菌门、绿弯菌门,相对丰度占比超过82%;真菌群落则为子囊菌门和担子菌门,占比超过85%,AFF担子菌门相对丰度最高而子囊菌门最低。(3)RDA分析显示,土壤pH和乔木物种多样性(Shannon指数)是影响微生物群落结构变化的主导因子;土壤养分元素对细菌群落影响不显著,真菌群落主要受TN、TP含量显著影响。总体上,林型间乔木层物种多样性、土壤酸碱度及其氮磷含量是导致微生物群落结构变化的关键因素。

To understand the change and distinction of the top-soil microbial community structure and its diversity,three natural secondary forests(Davidii-Betula platyphylla-B.albosinensis broad-leaved forest,ABB;Betula platyphylla-Acer davidii-Abies faxoniana mixed coniferous and broad-leaved forest,BAA;Abies faxoniana forest,AFF)were investigated based on the background of similar microclimate and soil parent materials in Miyaluo forest area of western Sichuan,where the forests formed by natural regeneration after logging in the 1960s.Chemical properties of soil and species diversity of plant community were analyzed.We used high-throughput sequencing of top-soil DNA to analyze soil bacterial and fungal community composition.The results implied that the forest types significantly changed the soil microbial community composition.The Shannon index of soil fungi communities differed dramatically among the three natural secondary forests,but had no significant differences in soil bacterial communities.Furthermore,Chao1 and Shannon index of soil bacteria were significantly higher than those of fungi.Proteobacteria,Acidobacteria,Verrucomicrobia,Bacteroidetes,Chloroflexi were the dominant phyla among three secondary forests,accounting for more than 82%.Ascomycota and Basidiomycota of fungal communityaccounted for over 85%.Redundancy analysis results showed that soil pH and Shannon index of tree layer were the main factors governing soil bacterial and fungal community structure,while soil TN(Total nitrogen)and TP(Total phosphorus)contents largely explained the shift in the fungal community structure.In general,our results provide insights into the importance of species composition of tree layer,soil acidity,TN and TP content in affecting soil microbial community composition and diversity,while providing reference for the mechanisms of carbon and nitrogen sequestration and soil microbial diversity in natural secondary forest resource management and conservation.