【目的】研究不同植被覆盖下湿地土壤有机碳组成、微生物群落结构的特征,为合理开发利用、恢复和保护湿地生态功能提供依据。【方法】以江苏洪泽湖与淮河交汇区湿地自然植被类型(湖草滩、芦苇滩)和人工植被类型(杨树林、柳树林)的土壤为研究对象,应用物理分组的方法研究土壤不同粒径 (<2 μm、≥2~63 μm、≥63~200 μm、≥200~2 000 μm) 组分分布、有机碳含量与分布情况,采用高通量测序技术对土壤微生物群落结构特征进行表征,运用聚类分析、冗余分析研究不同植被类型土壤中微生物物种丰度相似性、微生物群落结构与不同粒径组分土壤有机碳及土壤理化性质之间的关系。【结果】①洪泽湖与淮河交汇区湿地人工植被类型林地中土壤粒径≥200~2 000 μm组分分布最少,土壤粒径≥2~63和≥63~200 μm组分分布显著高于其他粒径组分;人工植被类型土壤总有机碳含量显著高于自然植被类型,其中各植被类型各粒径组分(除粒径≥2~63 μm组分)土壤有机碳含量大小顺序均为柳树林>杨树林>湖草滩>芦苇滩;粒径< 2 μm组分的土壤有机碳分布比例显著高于其他粒径组分的,粒径≥200~2 000 μm组分的土壤有机碳分布比例低于其他粒径组分的。②各植被类型土壤微生物群落多样性(Shannon 指数)大小顺序均为芦苇滩>湖草滩>柳树林>杨树林,变形菌门(Proteobacteria)、酸杆菌门(Acidobacteria)是样地土壤细菌的主要优势种群(50.21%~66.12%);子囊菌门(Ascomycota)、担子菌门(Basidiomycota)是土壤真菌的主要优势种群(68.32%~95.11%)。土壤细菌群落聚类分析相似性系数最高的是湖草滩和芦苇滩,这个聚类和杨树林的土壤细菌群落相似性较远;真菌群落聚类分析中,湖草滩和芦苇滩的真菌群落自成一族群;杨树林和柳树林的真菌群落聚为另一族群。③微生物群落结构与土壤理化性质相关性分析显示,土壤有机碳含量和含水量是影响土壤微生物群落结构的主要因子,细菌中的酸杆菌门(Acidobacteria)和真菌中的担子菌门(Basidiomycota)受粒径<2 μm、≥2~63 μm、≥63~200 μm组分的土壤有机碳分布影响很大。【结论】洪泽湖湿地4种植被覆盖下不同粒径组分土壤的质量和有机碳含量数值呈现两头小中间大趋势,不同粒径组分中有机碳分布比例随粒径的增加而降低。种植人工植被(柳树林、杨树林)有利于增加土壤有机碳的含量,但人工植被类型未增加土壤微生物的多样性,粒径<200 μm组分的土壤有机碳分布可能影响特定的优势微生物类群。

【Objective】This study was conducted to understand the effects of natural vegetation types (lake-grass marsh and reed marsh) and artificial vegetation types (poplar forest and willow forest) on soil organic carbon and microbial community structure in the intersection area of Hongze Lake.【Method】The particle size distribution, and the content and distribution of soil organic carbon (SOC) in different particle-size fractions of soils (<2, ≥2-63, ≥63-200 and ≥200-2 000 μm) were measured, and the soil microbial community structure was characterized by high-throughput sequencing. We utilized the cluster analysis to investigate the relationship of microbial species and the reliability analysis to examine the relationships between the microbial community structure, SOC and soil physical and chemical properties.【Result】① The particle size distribution was the lowest in the ≥200-2 000 μm fraction and was significantly higher in the ≥2-63 and ≥63-200 μm fractions. Distribution of SOC in the ≥200-2 000 μm fraction was lower than that in the other soil fractions. SOC from the artificial forest soil was significantly higher than that in soils covered by natural vegetation types, with the content of SOC in various particle size fractions decreasing in the order of willow > poplar > lake grass > reed. With respect to different particle size fractions (except for ≥2-63 μm), the SOC contents were the highest in soils under cover of willow and lowest in reed-covered soils, and the distribution of SOC in the <2 μm fraction was significantly higher than that in other fractions. ② The diversity of the soil bacterial community in the four sites decreased in the order of reed > lake grass > willow > poplar, and the diversity of the soil fungi community decreased in the order of reed > willow > lake grass > poplar. Proteobacteria and Acidobacteria were the dominant phyla of soil bacteria in the study area (accounting for 50.21%-66.12%), whereas Ascomycota and Basidiomycota were the dominant phyla of soil fungi (accounting for 68.32%-95.11%). The highest similarity coefficient obtained from the soil bacterial community cluster analysis was for lake-grass marsh and reed marsh. The soil bacterial community significantly differed from that of the poplar forest. The community clustering analysis revealed that fungal communities in the soils of lake-grass marsh and reed marsh formed similar communities, while fungal communities in the soils of the poplar forest and willow forest clustered into another group. ③ The correlation analysis of the microbial community structure and soil physical and chemical properties showed that the SOC content and water content were the main factors affecting the soil microbial community structure. Acidobacteria and Basidiomycota were positively correlated with the SOC content in the particle size fractions of <2, ≥2-63 and ≥63-200 μm. Basidiomycota showed a significant negative correlation with the soil moisture content, indicating that Basidiomycota abundance would increase with the increase in SOC particle size components when soil moisture was relatively low.【Conclusion】In soil fractions of different particle sizes under four different vegetation cover types in Hongze Lake Wetlands, both the particle size distribution and content of SOC showed a large trend of two small middles. All of them show an inverted “V” plot, and the distribution of SOC in soils with different particle sizes decreased with increasing particle sizes. We conclude that the establishment of artificial forests in the Hongze Lake Wetland has been conducive to the accumulation of SOC but has not affected the diversity of the microbial community. SOC components and their effectiveness may be the limiting factors for microbial diversity.