根系分泌碳输入对刺槐凋落叶细菌群落结构的影响
Effects of Root Exudation Carbon Inputs on the Structure of Bacterial Microbial Communities during Symplocos Lucida Litter Decomposition

为深入理解根系分泌碳输入对凋落物分解细菌群落的调节作用，在刺槐凋落叶分解环境中添加不同浓度的模拟根系分泌物碳溶液(每g土壤添加CK 0 mg、L 0.27 mg、M 0.54 mg、H 1.08 mg碳)，通过45 d的室内培养后，采用16S rRNA测序研究外源根系分泌碳对刺槐凋落叶表面细菌群落的影响。结果表明：1) 各处理间细菌群落的丰富度无差异，但中、高浓度(M和H)的分泌碳输入显著提高了其多样性。2) 变形菌门(Proteobacteria)、浮霉状菌门(Planctomycetes)、放线菌门(Actinobacteria)、拟杆菌门(Bacteroidetes)和酸杆菌门(Acidobacteria)是刺槐凋落物的主要分解细菌类群。3) 变形菌门和放线菌门的丰度对于分泌碳输入浓度的响应特征具有低促高抑的现象；同时较高浓度的根系分泌碳输入处理(H)促进了拟杆菌门的繁殖。4) 刺槐凋落叶表面细菌功能群以化学异养和好氧化学异养为主，固氮类、碳氢化合物降解类和纤维素分解类功能基因的丰度随着输入分泌碳浓度的增加而逐步提高。研究结果有助于理解根系分泌物对凋落物降解细菌群落的影响机制，为深入揭示根系–微生物–凋落物降解互作效应提供一定理论依据。
To understand how root exudates influence litter decomposition in forest ecosystems, different concentrations of simulated root exudate carbon solutions (CK 0, L 0.27, M 0.54, H 1.08 mg C per gram of soil) were added to the Symplocos lucida litter decomposition environment. After 45 days of laboratory incubation, the impact of different carbon input levels on the bacterial community was assessed using 16S rRNA sequencing. The results showed that: 1) There was no significant difference in the richness of bacterial communities among the treatments, but the input of medium and high concentrations (M and H) of exudate carbon significantly increased their diversity. 2) Proteobacteria, Planctomycetes, Actinobacteria, Bacteroidetes, and Acidobacteria were the main bacterial phyla involved in the decomposition of Symplocos lucida litter. 3) The abundance of Proteobacteria and Actinobacteria exhibited a low promotion-high inhibition response to the concentration of exudate carbon input. Additionally, the higher concentration of root exudate carbon input (H) promoted the proliferation of Bacteroidetes. 4) The functional groups of bacteria on the surface of Symplocos lucida litter were primarily associated with chemoheterotrophy and aerobic chemoheterotrophy. The abundance of functional genes related to nitrogen fixation, hy-drocarbon degradation, and cellulolysis increased gradually with the increase in exudates carbon input concentration. Overall, these research findings contribute to the understanding of the mechanisms by which root exudates influence the bacterial community involved in litter decom-position. They also provide a theoretical basis for further revealing the interactions among roots, microorganisms, and litter decomposition processes.