Data from: Do temperate tree species diversity and identity influence soil microbial community function and composition?

Studies of biodiversity-ecosystem function in treed ecosystems have generally focused on aboveground functions. The present study investigates inter-trophic links between tree diversity and soil microbial community function and composition.We examined how microbial communities in surface mineral soil responded to experimental gradients of tree species richness (SR), functional diversity (FD), community-weighted mean trait value (CWM) and tree identity. The site was a 4-yr-old common garden experiment near Montreal, Canada, consisting of deciduous and evergreen tree species mixtures. Microbial community composition, community-level physiological profiles (CLPP) and respiration were evaluated using phospholipid fatty acid (PLFA) analysis and the MicroRespTM system, respectively. The relationship between tree species richness and glucose induced respiration (GIR), basal respiration (BR), metabolic quotient (qCO2) followed a positive but saturating shape. Microbial communities associated with species mixtures were more active (basal respiration (BR)), with higher biomass (glucose induced respiration (GIR)), and used a greater number of carbon sources than monocultures. Communities associated with deciduous tree species used a greater number of carbon sources than those associated with evergreen species, suggesting a greater soil carbon storage capacity. There were no differences in microbial composition (PLFA) between monocultures and SR mixtures. The FD and the CWM of several functional traits affected both BR and GIR. In general, the CWM of traits had stronger effects than did FD, suggesting that certain traits of dominant species have more effect on ecosystem processes than does FD. Both the functions of GIR and BR were positively related to aboveground tree community productivity. Both tree diversity (SR) and identity (species and functional identity – leaf habit) affected soil microbial community respiration, biomass and composition. For the first time, we identified functional traits related to life history strategy, as well as root traits that influence another trophic level, soil microbial community function, via effects on BR and GIR.

针对林木生态系统中生物多样性-生态系统功能的相关研究，通常多聚焦于地上生态功能。本研究探究了树木多样性与土壤微生物群落功能及组成之间的跨营养级联系。我们分析了表层矿质土壤中的微生物群落如何响应树木物种丰富度（SR）、功能多样性（FD）、群落加权平均性状值（CWM）以及树种组成的实验梯度。本实验点位位于加拿大蒙特利尔附近，是一项为期4年的同质园（common garden）实验，设置了落叶与常绿树种的混交组合。研究分别采用磷脂脂肪酸（PLFA）分析与MicroResp™系统，测定了微生物群落组成、群落水平生理剖面（CLPP）以及土壤呼吸速率。树木物种丰富度与葡萄糖诱导呼吸（GIR）、基础呼吸（BR）以及代谢商（qCO2）之间的关系呈现出正向且饱和的曲线模式。相较于单一树种林分（monocultures），混交林分关联的微生物群落活性更高（以基础呼吸BR表征）、生物量更大（以葡萄糖诱导呼吸GIR表征），且可利用的碳源种类更多。与落叶树种关联的微生物群落可利用的碳源种类多于常绿树种关联的群落，这暗示前者具备更强的土壤碳固存能力。单一树种林分与物种丰富度梯度混交林分之间的微生物群落组成（PLFA表征）并无显著差异。多项功能性状的功能多样性（FD）与群落加权平均性状值（CWM）均对BR与GIR产生影响。总体而言，性状的CWM相较于FD对生态系统过程的影响更为显著，表明优势物种的特定性状对生态系统过程的作用要强于功能多样性FD。GIR与BR这两项微生物功能指标均与地上树木群落生产力呈正向相关关系。树木多样性（SR）与树种组成（物种组成与功能组成——即叶片习性）均会对土壤微生物群落的呼吸、生物量以及组成产生影响。本研究首次明确了与生活史策略相关的功能性状，以及通过影响BR与GIR进而作用于另一营养级——土壤微生物群落功能的根系性状。