Table_3_Contrasting Responses of Rhizosphere Bacteria, Fungi and Arbuscular Mycorrhizal Fungi Along an Elevational Gradient in a Temperate Montane Forest of China.docx

Elevational gradients strongly affect microbial biodiversity in bulk soil through altering plant and soil properties, but the effects on rhizosphere microbial patterns remain unclear, especially at large spatial scales. We therefore designed an elevational gradient experiment to examine rhizosphere microbial (bacteria, fungi and arbuscular mycorrhizal fungi) diversity and composition using Illumina sequencing of the 16S rRNA and ITS genes for comparison to plant and soil properties. Our results showed that bacterial and fungal alpha diversity was significantly higher at mid-elevation, while AMF alpha diversity decreased monotonically. The beta diversities of the three groups were significantly affected by elevational gradients, but the effect on bacterial beta diversity was larger than on fungal and AMF beta diversity. Proteobacteria, the dominant phyla of bacteria, was significantly higher at the mid-elevation, while Acidobacteria and Actinobacteria significantly decreased as elevation increased. The main fungal taxa, Basidiomycota, significantly decreased with elevation, and Ascomycota significantly increased with elevation. Glomeromycota, the dominant AMF phyla, responded insignificantly to the elevational gradients. The responses of bacterial and fungal alpha diversity were mostly associated with tree diversity and organic carbon, whereas AMF alpha diversity mainly depended on litter N and P. Changes in bacterial community composition along the elevational gradient were explained primarily by litter N and P, and litter P was the main driver of fungal and AMF community composition. Overall, our results suggest that plant litter, particularly litter N and P, were the main source of external carbon input and drove the observed differences in rhizosphere microbial diversity and community composition. Our results highlight the importance of litter nutrition in structuring rhizosphere microbial communities in mountain ecosystems.

海拔梯度对土壤微生物多样性产生显著影响，这种影响通过改变植物和土壤特性来实现，然而，对根际微生物模式的影响，尤其是在大尺度空间上，尚不明确。鉴于此，我们设计了一项海拔梯度实验，通过Illumina测序16S rRNA和ITS基因，以考察根际微生物（细菌、真菌和丛枝菌根真菌）的多样性和组成，并将其与植物和土壤特性进行比较。我们的研究结果表明，细菌和真菌的α多样性在中海拔处显著较高，而丛枝菌根真菌的α多样性呈单调下降趋势。三个组的β多样性均受到海拔梯度的影响，但细菌的β多样性受影响程度大于真菌和丛枝菌根真菌的β多样性。细菌中的优势门类变形菌在海拔中段显著增加，而酸杆菌和放线菌随海拔升高显著减少。主要真菌类群担子菌亚门随海拔升高显著减少，子囊菌亚门随海拔升高显著增加。丛枝菌根真菌中的优势门类球囊菌门对海拔梯度的反应不显著。细菌和真菌的α多样性的变化主要与树木多样性和有机碳有关，而丛枝菌根真菌的α多样性主要依赖于凋落物中的氮和磷。沿着海拔梯度的细菌群落组成变化主要由凋落物中的氮和磷解释，而凋落物中的磷是真菌和丛枝菌根真菌群落组成变化的主要驱动因素。总体而言，我们的研究结果表明，植物凋落物，尤其是凋落物中的氮和磷，是外部碳输入的主要来源，并驱动了观察到的根际微生物多样性和群落组成的差异。我们的研究结果强调了凋落物营养在构建山地生态系统根际微生物群落中的重要性。