土壤基质影响下叶凋落物际细菌群落特征及其与分解速率的关联性

Characteristics of bacterial communities in the leaf detritusphere under the influence of soil and their association with decomposition rates

植物凋落物在土壤有机质形成过程中扮演重要角色,在局域尺度上其分解速率与土壤生境密切相关。不同土壤基质下的凋落物分解快慢不同,进而影响土壤碳周转及养分利用效率。与叶凋落物分解密切相关的微生物群落主要来源于叶凋落物际,这些微生物群落在土壤养分循环和有机物分解过程中发挥着至关重要的作用,然而目前关于叶凋落物际中微生物群落动态变化的研究还相对较少。研究以喜旱莲子草(Alternanthera philoxeroides)的叶凋落物为研究对象,通过高通量测序研究不同土壤(有机土、铁铝土、冲积土)和分解阶段(30%、60%、90%)下叶凋落物际细菌群落的动态变化及其对凋落物分解的影响。结果表明:随着分解的进行,叶凋落物际细菌群落多样性逐渐升高,并且群落多样性水平越高(Alpha多样性:有机土>冲积土>铁铝土),其分解速率越快(k:有机土>冲积土>铁铝土)。研究进一步发现,叶凋落物际细菌群落组成变化受土壤类型和分解阶段显著影响(P<0.001),但前者作用效应更大。具体而言,不同土壤基质下的叶凋落物际优势菌不同,有机土和冲积土基质中均由变形菌门(Proteobacteria)主导(分别占55.33%和53.10%),铁铝土基质中则以放线菌门(Actinobacteriota)为主(占比为63.95%)。受分解阶段影响,不同土壤基质下叶凋落物际各优势菌门的平均相对丰度在分解后期均有所下降,而以绿弯菌门(Chloroflexi)为代表的寡营养菌(oligotrophic taxa)在分解后期显著增加(P<0.05),与分解前期相比增加了5.66—413.80倍。此外,在不同土壤中,叶凋落物际细菌群落构建均受确定性过程影响,其共现网络复杂度在冲积土、有机土、铁铝土中依次降低,变形菌门和放线菌门在整个叶凋落物际细菌群落的构建和维持中扮演着关键角色。研究揭示了不同土壤基质调控叶凋落物际细菌群落组成及多样性进而影响凋落物分解过程,这为深入理解叶凋落物际细菌群落在生态系统养分循环过程中的关键作用提供了数据支撑。

Plant litter plays a pivotal role in the formation of soil organic matter,with its decomposition rate closely associated with the soil habitat at local scale.The pace of litter decomposition varies across different soils,consequently influencing soil carbon turnover and nutrient utilization efficiency.The microbial communities closely associated with leaf litter decomposition primarily originate from the leaf detritusphere.These microbial communities play a crucial role in the soil nutrient cycling and the decomposition of organic matter.However,current research on the dynamic changes in microbial communities within the leaf detritusphere is relatively limited.This research focused on the leaf litter of Alternanthera philoxeroides,examining the dynamic changes in the bacterial communities of the leaf detritusphere across different soils(Histosols,Ferralosols,and Alluvial soil)and decomposition stages(30%,60%,and 90%)through high-throughput sequencing.The results indicated that as decomposition progressed,the diversity of bacterial communities in the leaf detritusphere gradually increased,and higher levels of community diversity(Alpha diversity:Histosols>Alluvial soil>Ferralosols)correlated with faster decomposition rates(k:Histosols>Alluvial soil>Ferralosols).The study further revealed that changes in the composition of bacterial communities in the leaf detritusphere were significantly affected by both soil type and decomposition stage,with the former exerting a greater influence(P<0.001).Specifically,the dominant bacteria in the leaf detritusphere varied with soil,with Proteobacteria leading in both Histosols and Alluvial soil(55.33%and 53.10%,respectively),while Actinobacteriota predominated in Ferralosols(63.95%).Influenced by the decomposition stage,the average relative abundance of each dominant phylum within the leaf detritusphere across different soils decreased in the later stages of decomposition.Conversely,oligotrophic taxa,represented by Chloroflexi,significantly increased in the later stages of decomposition(P<0.05),with increases ranging from 5.66 to 413.80 times compared to the early stages of decomposition.Moreover,in various soils,the assembly of bacterial communities in the leaf detritusphere was influenced by deterministic processes,with the complexity of their co-occurrence networks decreasing in the order of Alluvial soil,Histosols,Ferralosols.Proteobacteria and Actinobacteriota played key roles in the construction and maintenance of the entire leaf detritusphere bacterial community.This study reveals how different soils regulate the composition and diversity of bacterial communities in the leaf detritusphere,thereby influencing the decomposition process of litter.It provides data support for a deeper understanding of the key role played by bacterial communities in the leaf detritusphere in the nutrient cycling process of ecosystems.