森林次生演替和土壤层次对微生物群落结构的影响

Effects of forest secondary succession and soil depth on microbial community structure

森林次生演替与生态系统结构和功能的动态变化密切相关。大多数研究主要关注植物群落以及土壤有机碳(SOC)的变化,然而土壤微生物群落如何响应森林次生演替还需要进一步探究。本研究以长白山森林次生演替序列(20、80、120、200和≥300年)和两个土壤层次为对象,采用磷脂脂肪酸微生物标志物,探究温带森林次生演替过程中地下微生物群落结构变化。森林次生演替改变了土壤微生物群落结构,主要归因于某些特定微生物类群的变化,演替前期革兰氏阴性菌和腐生真菌占主导,而在演替后期革兰氏阳性菌和丛枝菌根真菌占主导。另外,土壤有机质数量和质量差异是影响微生物群落结构和生物量的主要环境因素。森林演替前期和中期增加的SOC含量促进了微生物生物量,而演替后期增加的难分解芳香族有机组分抑制了微生物生物量合成。土壤层次间理化性质的差异导致微生物群落变化,有机质层高的SOC以及氮含量导致更多微生物生物量的合成。微生物群落在时间和空间尺度的变化及其驱动因素反映了生态系统结构和功能对环境变化的响应。

Forest secondary succession closely relates with the dynamics of ecosystem structure and function.Previous studies have reported the changes of plant community and soil organic carbon(SOC)during forest succession,with limited understanding of the responses of soil microbial community.Here,we explored the changes of soil microbial community structure(represented by phospholipid fatty acid)across secondary forest succession(20,80,120,200,and≥300 years)and soil depth(topsoil and subsoil).We demonstrated that the changes in microbial community structure among forest successional stages were ascribed to the specific microbial functional groups.Soil microbial community was dominated by Gram-negative bacteria and saprotrophic fungi at early-successional stages,and by Gram-positive bacteria and arbuscular mycorrhizal fungi at late-successional stages.Quantity and quality of soil organic matter(SOM)were the predominant factors driving soil microbial community structure and biomass.The increase in SOC contents at early and middle successional stages stimulated microbial biomass,and the increase in soil aromatic compounds suppressed microbial biomass at late-successional stages.Soil microbial community was affected by the varied soil physicochemical properties between topsoil and subsoil,e.g.,high SOC content in topsoil correlated with microbial biomass.Our findings suggest that changed soil microbial community and its driving factors in temporal and spatial scales reflect the response of ecosystem structure and function to environmental change.