关键词: 湿地, 植被类型, 土壤有机碳, 粒径组分, 微生物群落, 高通量测序, 洪泽湖

Abstract:

【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.

Key words: wetland, vegetation type, soil organic carbon (SOC), particle size fraction, microbial community, high-throughput sequencing, Hongze Lake