浑善达克沙地生物土壤结皮及其下层土壤中固氮细菌群落结构和多样性

【背景】荒漠化是一个重大环境问题,生物土壤结皮(Biological soil crusts,BSCs)可遏制荒漠化,其中的固氮微生物对BSCs的形成和发育有重要作用,但目前BSCs中固氮细菌群落结构和多样性尚不十分清楚。【目的】阐明浑善达克沙地中不同类型生物土壤结皮及其下层土壤固氮细菌的群落结构、多样性及其影响因素。【方法】利用稀释热法和碱解扩散法检测土壤的有机质(Organic matter,OM)和速效氮(Available nitrogen,AN)含量;利用高通量测序对nifH基因进行测序,基于nifH序列比较分析固氮细菌群落结构和多样性;利用典范对应分析(Canonical correlation analysis,CCA)分析群落、样品和土壤理化参数的相关性。【结果】固氮细菌优势菌门除在苔藓结皮(HSM)中为Cyanobacteria和Proteobacteria外,在其他类型BSCs中均只为Cyanobacteria;苔藓结皮下层土壤(HSMs)(下层土壤中只有HSMs检测到了nifH)优势菌门为Proteobacteria,优势菌纲为Alphaproteobacteria和Betaproteobacteria;优势菌属差异较大,藻结皮(HSA)中Unclassified_f_Nostocaceae占90.99%;地衣结皮(HSL)中Scytonema和Unclassified_f_Nostocaceae分别占45.85%和44.14%;HSM中Unclassified_f_Nostocaceae、Scytonema、Nostoc、Skermanella、Unclassified_o_Nostocales分别占29.21%、22.57%、15.34%、14.74%和10.60%;HSMs中Skermanella、Azohydromonas、Unclassified_p_Proteobacteria、Unclassified_c_Alphaproteobacteria分别占33.80%、25.66%、18.20%和10.62%;固氮细菌多样性随结皮的发育逐渐提高;OM和AN对结皮的发育起促进作用。【结论】藻结皮、地衣结皮和苔藓结皮及其紧邻下层土壤中的固氮细菌群落结构和多样性差异明显,且固氮细菌类群和多样性指数随BSCs发育阶段的提高而增加。本研究为认识和利用生物土壤结皮相关固氮细菌提供了基础依据。

Community structure and diversity of diazotrophs in biological soil crusts and soil underneath crust of Hunshandake deserts

Background] Desertification is a major environmental problem, biological soil crusts (BSCs) can inhibit desertification, and the diazotrophs play an important role in the formation and development of BSCs. However, the community structure and diversity of diazotrophs in BSCs are not clear enough. Objective] To clarify the community structure and diversity of diazotrophs in different types of biological soil crusts (BSCs) and soils under them and the effectors of soil environmental factors. Methods] Using dilution heat method and alkali solution diffusion to measure the content of organic matter (OM) and the available nitrogen (AN) of soil, respectively; nifH gene was sequenced via the high-throughput sequencing platform, and the community structure, diversity and the variance analysis of diazotrophs were analyzed by bioinformatics analysis; Canonical Correlation Analysis (CCA) were used to analyze the correlation among the community structure, samples and the physico-chemical parameters of soil. Results] Dominant phylum were Proteobacteria and Cyanobacteria in moss crusts (HSM), Cyanobacteria in the other types of BSCs; the class of Alphaproteobacteria and Betaproteobacteria accounted for the most fraction in the soil underneath moss crusts (nifH was only detected in soil underneath moss crusts, HSMs); significant differences existed in community structure at genus level, algae crusts (HSA) was predominated by unclassified_f_Nostocaceae (90.99%), Lichen crusts (HSL) by Scytonema (45.85%) and unclassified_f_Nostocaceae (44.14%), HSM by unclassified_f_Nostocaceae (29.21%), Scytonema (22.57%), Nostoc (15.34%), Skermanella (14.74%), unclassified_o_Nostocales (10.60%), and HSMs by Skermanella (33.80%), Azohydromonas (25.66%), unclassified_p_Proteobacteria (18.20%) and unclassified_c_Alphaproteobacteria (10.62%). Conclusion] The community structure and diversity of diazotrophs in Algae, Lichen and Moss crusts and soil underneath crusts were markedly different, and the community species and the diversity increased with the development of the BSCs. This study provides a basis for appreciation and utilization of the diazotrophs in the BSCs.