Department of Agronomy & Center for Intensive Mediterranean Agrosystems and Agri-food Biotechnology (CIAIMBITAL), University of Almeria, E-04120, Almería, Spain.
Experimental Station of Arid Zones (CSIC), Almería, Spain.
Sci Total Environ. 2020 Mar 20;709:134654. doi: 10.1016/j.scitotenv.2019.134654. Epub 2019 Dec 5.
Biocrusts are an important drylands landscape component, which enriches the upper millimeters of the soil with organic matter and initiates biogeochemical cycles. However, little is known about the influence of biocrusts on soil bacterial community structure and diversity. Different biocrust types representing a successional gradient were studied. This gradient, from the earliest to the latest successional stages, consisted of an incipient cyanobacterial biocrust < mature cyanobacterial biocrusts < biocrust dominated by the Squamarina lentigera and Diploschistes diacapsis lichens < Biocrust characterized by the Lepraria isidiata lichen. Moreover, in each biocrust type, four different percentages of biocrust cover were also selected. Soil diversity gradually increased with biocrust successional stage and percentage of biocrust cover. The biocrust cover had an important role in the total abundance of bacteria, generally increasing in soils colonized by the highest percentages of cover. Biocrust successional stage was the most important factor, significantly influencing 108 soil bacteria genera, whereas biocrust cover showed significant differences in only 10 genera. Principal Component Analysis showed contrasting microbial composition across the biocrust successional gradient. Some bacterial taxa were dominant in the soil colonized by different biocrust types. Thus, Leptolyngbya, Rubrobacter, Solirubrobacter, Geodermatophilus, etc., were more abundant in incipient cyanobacteria; Nostocales, Chroococcidiopsaceae, Coleofasciculaceae etc., under mature cyanobacterial biocrusts; Truepera, Sphingobacteriaceae, Actinophytocola, Kribella, etc., below the S. lentigera and D. diacapsis community, and Bryobacter, Ohtaekwangia, Opitutus, Pedosphaeraceae, etc., in soils colonized by L. isidiata. Several soil bacteria taxa showed significant correlations (p < 0.05) with chemical soil properties (pH, total nitrogen, total organic carbon, available phosphorous and electrical conductivity). We discuss the role of biocrusts influencing these chemical soil parameters, including the presence of certain metabolites secreted by biocrusts, and also their effects on soil moisture and several physical soil features, as well as their association with different microclimates, all of which could favor a more selective environment for certain bacteria.
生物结皮是干旱地区的重要景观组成部分，它在土壤的上层几毫米中积累有机物并启动生物地球化学循环。然而，人们对生物结皮对土壤细菌群落结构和多样性的影响知之甚少。本研究选择了不同的生物结皮类型来代表演替梯度，从最早到最晚的演替阶段，包括初期蓝藻生物结皮<成熟蓝藻生物结皮<地衣 Squamarina lentigera 和 Diploschistes diacapsis 占优势的生物结皮< Lepraria isidiata 地衣占优势的生物结皮。此外，在每种生物结皮类型中，还选择了四个不同的生物结皮盖度百分比。土壤多样性随着生物结皮演替阶段和生物结皮盖度百分比的增加而逐渐增加。生物结皮盖度对细菌的总丰度有重要作用，通常在被最高百分比盖度的土壤中增加。生物结皮演替阶段是最重要的因素，显著影响了 108 个土壤细菌属，而生物结皮盖度仅在 10 个属中表现出显著差异。主成分分析显示，生物结皮演替梯度上的微生物组成存在差异。一些细菌类群在不同生物结皮类型的土壤中占优势。因此，Leptolyngbya、Rubrobacter、Solirubrobacter、Geodermatophilus 等在初期蓝藻中更为丰富；Nostocales、Chroococcidiopsaceae、Coleofasciculaceae 等在成熟蓝藻生物结皮中；Truepera、Sphingobacteriaceae、Actinophytocola、Kribella 等在 S. lentigera 和 D. diacapsis 群落下；Bryobacter、Ohtaekwangia、Opitutus、Pedosphaeraceae 等在 L. isidiata 定植的土壤中。一些土壤细菌类群与土壤化学性质（pH 值、总氮、总有机碳、有效磷和电导率）呈显著相关（p<0.05）。我们讨论了生物结皮影响这些土壤化学参数的作用，包括生物结皮分泌的某些代谢物的存在，以及它们对土壤水分和几种物理土壤特性的影响，以及它们与不同小气候的关联，所有这些都可能为某些细菌提供更具选择性的环境。
