艾比湖湿地盐节木土壤固氮微生物群落结构和丰度的环境异质性特点

Environmental heterogeneity of the nitrogen-fixing microbial community structure and abundance in the soil surrounding Halocnemum strobilaceum in Ebinur Lake wetland

摘要:

【背景】新疆艾比湖湿地国家自然保护区作为国内最典型的温带干旱区湿地荒漠生态系统，对于富集生物多样性、平衡生态环境等方面存在着非凡的意义。目前关于艾比湖湿地根际与非根际土壤固氮微生物群落结构和丰度的相关研究还未见报道。【目的】通过分析新疆艾比湖湿地盐节木根际和非根际土壤固氮菌nifH基因的群落结构和丰度的环境异质性特点，及探讨微生物群落对国内极端干旱区脆弱敏感的艾比湖湿地生态系统循环过程中的作用，为改善荒漠化的艾比湖湿地环境提供理论依据。【方法】采用构建克隆文库和q-PCR的方法，并利用冗余分析法(Redundant analysis，RDA)探究土壤理化性质与固氮微生物群落结构及丰度的相关性。【结果】艾比湖湿地盐节木非根际土壤中nifH的多样性高于根际土壤，盐节木根际土壤的nifH序列优势种属主要为固氮根瘤菌属(Azorhizobium)和脱硫弧菌属(Desulfovibrio)；非根际土壤的nifH序列优势种属主要是固氮弧菌属(Azoarcus)、太阳杆菌属(Heliobacterium modesticaldum)和脱硫弧菌属(Desulfovibrio)。盐节木根际土壤nifH数量为4.08×104 copies/g，盐节木非根际土壤中nifH的数量为5.52×103 copies/g，根际土壤nifH的丰度高于非根际土壤。相关性分析显示，根际土壤的优势类群和丰度与硝态氮(NO3?-N)、速效氮、总钾、含水量等因子显著相关，非根际土壤的优势类群和丰度与硝态氮(NO3?-N)、速效氮、总磷、总钾、总氮呈显著相关。【结论】在盐节木根际土壤中nifH的丰度高于非根际土壤，而多样性则低于非根际土壤，而且硝态氮(NO3?-N)、速效氮、总磷可能会影响固氮微生物的群落结构和丰度，这些特点为湖泊湿地的退化恢复提供理论和数据基础。

Abstract:

[Background] The Ebinur Lake wetland national nature reserve in Xinjiang is one of the most representative temperate arid regions wetland desert ecosystems in China, and plays an important role in maintaining regional ecological balance. At present, there has not been any report on the structure and abundance of nitrogen-fixing microorganisms in rhizosphere and non-rhizosphere soil at Ebinur Lake wetland. [Objective] To explore the characteristics of environmental heterogeneity of community structure and abundance of nitrogen fixation gene (nifH) in the soil rhizosphere and non-rhizosphere soil nitrogen-fixing microbial of Halocnemum strobilaceum in Ebinur Lake wetland in Xinjiang. Based on this, the potential forces of the microbial communities in the desertification and continuous salinization of the Ebinur Lake wetland ecosystem in the temperate arid regions are explored, providing the theoretical and data basis for the degradation and restoration of lake wetlands. [Methods] The correlations among soil physicochemical properties, microbial community structure and microbe abundance were investigated by using the methods of constructing clone library, q-PCR and redundant analysis (RDA). [Results] The results showed that the diversity of nifH gene in non-rhizosphere soil were higher than that in rhizosphere soil. The dominant species of nifH sequence were Azorhizobium and Desulfovibrio in the rhizosphere soil, Azoarcus, Heliobacterium modesticaldum and Desulfovibrio in non-rhizosphere soil. The number of nifH gene was 4.08×104 copies/g in rhizosphere soil and 5.52×103 copies/g in non-rhizosphere soil. The abundance of nifH in rhizosphere soil is higher than that in non-rhizosphere soil. Correlation analysis showed that the dominant groups and abundance of containing nifH bacteria in rhizosphere soil were significantly related with nitrate nitrogen (NO3?-N), available nitrogen (AN), total potassium (TK), soil moisture (SM) and other factors, and with nitrate nitrogen (NO3?-N), available nitrogen (AN), total phosphorus (TP), total potassium (TK) and total nitrogen (TN) in non-rhizosphere soil. [Conclusion] These results indicated that the abundance of nifH bacteria in rhizosphere soil was higher than that in non-rhizosphere soil, while the diversity was lower than that in non-rhizosphere soil. Nitrate nitrogen (NO3?-N), available nitrogen (AN), total phosphorus (TP) may affect the community structure and abundance of nitrogen-fixing microorganisms. These characteristics provide the theoretical and data basis for the degradation and restoration of lake wetlands.