Soil microbial community composition

Phospholipid ester-linked fatty acid (PLFA) profiles were used to evaluate soil microbial community composition for 9 land use types in two coastal valleys in California. These included irrigated and non-irrigated agricultural sites, non-native annual grasslands and relict, never-tilled or old field perennial grasslands. All 42 sites were on loams or sandy loams of similar soil taxa derived from granitic and alluvial material. We hypothesized that land use history and its associated management inputs and practices may produce a unique soil environment, for which microbes with specific environmental requirements may be selected and supported. We investigated the relationship between soil physical and chemical characteristics, management factors, and vegetation type with microbial community composition. Higher values of total soil C, N, and microbial biomass (total PLFA) and lower values of soil pH occurred in the grassland than cultivated soils. The Correspondence Analysis of the PLFA profiles and the Canonical Correspondence Analysis of PLFA profiles, soil characteristics, and site and management factors showed distinct groups for land use types. A given land use type could thus be identified by soil microbial community composition as well as similar soil characteristics and management factors. Differences in soil microbial community composition were highly associated with total PLFA, a measure of soil microbial biomass, suggesting that labile soil organic matter affects microbial composition. Management inputs, such as fertilizer, herbicide, and irrigation, also were associated with the distinctive microbial community composition of the different cultivated land use types. Further uses of gradients in microbial ecology and implications for soil quality and restoration are discussed.

本研究采用磷脂脂肪酸酯（Phospholipid ester-linked fatty acid, PLFA）谱图分析方法，对美国加利福尼亚州两处沿海山谷中的9种土地利用类型的土壤微生物群落组成开展评估。研究涵盖灌溉与非灌溉农业用地、非原生一年生草原，以及遗迹性、从未耕作或弃耕旧地的多年生草原。全部42个样地的土壤均为源自花岗岩与冲积物的壤土或砂质壤土，且所属土壤分类单元相近。本研究提出假说：土地利用历史及其伴随的管理投入与管理措施，可塑造独特的土壤环境，进而筛选并维持具备特定环境适应性的微生物类群。本研究旨在探究土壤理化性质、管理因子与植被类型同土壤微生物群落组成之间的关联。结果显示，相较于耕作土壤，草原土壤的总有机碳、总氮及微生物生物量（总PLFA）水平更高，而土壤pH值更低。对PLFA谱图进行对应分析（Correspondence Analysis, CA），结合PLFA谱图、土壤特征、样地信息与管理因子的典范对应分析（Canonical Correspondence Analysis, CCA）结果表明，不同土地利用类型各自形成显著聚类。因此，可通过土壤微生物群落组成，结合相似的土壤特征与管理因子，对特定土地利用类型进行识别。土壤微生物群落组成的差异与表征土壤微生物生物量的总PLFA值高度相关，表明活性土壤有机质可对微生物群落组成产生影响。施肥、除草剂施用与灌溉等管理投入，同样与不同耕作土地利用类型下独特的微生物群落组成密切相关。本研究还探讨了微生物生态学梯度分析的进一步应用价值，及其对土壤质量评估与生态修复的启示。