摘要：
Bacteria,as a key component of biocrusts,which constitute up to or more than 70％ of the living cover in arid and semiarid lands worldwide,play the primary role in carbon and nitrogen inputs in deserts.Thus,changes in bacterial community structure and diversity can significantly alter their ecological processes and the functions of biocrusts.Sand burial is a common environmental stress of the biocrusts in arid and semiarid areas,yet little information is available regarding the effects of sand burial on bacterial community structure and diversity within biocrusts.Therefore,we adopted the high-throughput sequencing techniques to investigate the effects of sand burial on bacterial community structure and diversity of biocrusts dominated by Bryum argenteum following sand burial of 0 (control),0.5,2 and 10 mm in Shapotou,southeastern edge of the Tengger Desert.Bacterial community species composition,abundance variation,and diversity indices including the Shannon-Wiener diversity and the richness indices Chao and abundance-based coverage estimator were compared among biocrusts that suffered sand burial at various depths.The results showed the following:(1) In total,38 phyla,106 classes,and 181 genera were identified within biocrusts dominated by B.argenteum,of which the dominant bacterial phyla included Actinobacteria,Proteobacteria,Cyanobacteria,Planctomycetes,Bacteroidetes,and Acidobacteria,which comprised 78.4％-83.0％ of the whole community.(2) Principal component analysis showed that,compared to the control,the bacterial community structure was the most variable in soils at 2 and 10 mm depths.Sand burial induced significant changes inbacterial community composition;with the highest abundance were Cyanobacteria,Proteobacteria,Planctomycetes and Actinobacteria following 0,0.5,2 and 10 mm burial depths,respectively.With the increase in burial depth,the relative abundance of Actinobacteria,Proteobacteria,Planctomycetes,Bacteroidetes,Verrucomicrobia,Gemmatimonadetes,and FBP increased,while that of the phyla Cyanobacteria,Acidobacteria,and Chloroflexi decreased.In addition,the abundance of photosynthetic bacteria,nitrogen fixing bacteria,and mycelial genera of Actinobacteria all increased largely at 0.5 mm burial depth and decreased sharply at 2 and 10 mm burial depths.(3) The total count of bacteria,species richness,and microbial diversity of biocrusts dominated by B.argenteum increased following sand burial,among which the biocrusts subjected to 0.5 mm burial depth had the highest richness indices and biocrusts subjected to 2 mm burial depth had the highest diversity indices.The study demonstrated that various depths of sand burial had significant effects on bacterial community and diverse features within biocrusts dominated by B.argenteum in Shapotou and thus offered the theoretical foundation for further understanding of the influence mechanism of sand burial on the structure and ecological functions of biocrusts in arid desert areas.%作为干旱沙区常见干扰之一的沙埋显著影响着生物结皮的结构和功能,但其内在的生物学机理还不清楚.利用高通量测序技术,通过对0(对照)、0.5(浅层)、2和10 mm(深层)沙埋处理后的腾格里沙漠东南缘沙坡头地区真藓(Bryum argenteum)结皮层细菌群落物种组成与丰度的测定,研究了沙埋对真藓结皮层细菌群落结构和多样性的影响.结果表明:(1)共检测到沙坡头地区真藓结皮层细菌38门106纲181属,以放线菌、变形菌、蓝藻、浮霉菌、拟杆菌和酸杆菌等为主(占细菌群落的78.4％-83.0％);(2) PCA分析表明沙埋导致该地区真藓结皮层细菌群落结构组成发生明显改变.无沙埋时,真藓结皮层细菌群落中相对丰度最高的是蓝藻(18.6％),随着沙埋厚度的增加,依次变为变形菌(21.5％,沙埋厚度0.5 mm)、浮霉菌(21.5％,沙埋厚度2 mm)和放线菌(23.3％,沙埋厚度10 mm);浅层沙埋显著增加了真藓结皮层细菌群落中光合菌、固氮菌和产菌丝体细菌等关键功能菌的丰度,但深层沙埋降低了它们的丰度;(3)沙埋显著增加了真藓结皮层细菌群落多样性(P＜0.05)和物种丰富度(P＜0.05),0.5 mm沙埋后的细菌群落丰富度指数最高,2 mm沙埋后的结皮层细菌群落多样性指数最高.揭示了沙埋对干旱沙区真藓结皮层细菌群落结构与多样性的影响,为深入理解沙埋对沙区生物结皮结构和生态功能影响的生物学机制提供了一定的理论依据.
