Types Of Biological Soil Crusts Research Articles

Whole community shotgun metagenomes of two biological soil crust types from the Mojave Desert.

We present six whole community shotgun metagenomic sequencing data sets of two types of biological soil crusts sampled at the ecotone of the Mojave Desert and Colorado Desert in California. These data will help us understand the diversity and function of biocrust microbial communities, which are essential for desert ecosystems.

Spatial distribution and core community of diazotrophs in Biological soil crusts and subsoils in temperate semi-arid and arid deserts of China.

Biological soil crusts (BSCs) are distributed in arid and semiarid regions, and they function as important microhabitats for nitrogen fixation. The diazotroph community is critical for nitrogen fixation in BSCs and their subsoils. However, little is known about the key groups in different types of BSCs and subsoils in temperate semi-arid or arid deserts. Here, we sampled three types of BSCs and their subsoils from the Inner Mongolian plateau, investigated the distribution characteristics of the diazotroph community by high-throughput sequencing, predicted keystone species using the molecular ecological network analyses pipeline (MENAP), and verified their close relationship with the available nitrogen (AN) content. The results showed that available nitrogen content in BSCs was higher than that in subsoils in three different types of BSCs, and there were differences among seasons and according to the mean annual precipitation. The abundance of diazotrophs was higher in Cyano-BSCs, while diversity had no significant difference among BSCs and subsoils. Cyanobacteria and Proteobacteria, Nostocaceae and Scytonemataceae, Skermanella, Scytonema, Azohydromonas, Nostoc and Trichormus were the dominant phyla, families, and genera, respectively. The dominant groups belong to Skermanella, Scytonema, and Nostoc formed the core diazotroph community in the three types of BSCs and subsoils, and each had a close relationship with AN. These results indicate that diazotrophs in BSCs and subsoils had high diversity, and the core diazotroph communities have a close relationship with nitrogen fixation and that they may be the main contributor to nitrogen fixing in BSCs and subsoils in temperate deserts.

Morphology and distribution of biological soil crusts and their potential role in soil-forming processes under dry high-altitude periglacial conditions (Eastern Pamir, Tajikistan)

Under demanding climatic conditions that limit the development of vascular vegetation, biological soil crusts (BSCs) drive the processes of soil formation and nutrient sequestration. Though BSCs were studied in glacier forelands worldwide, the high-altitude areas with a combination of glaciation/deglaciation and arid or hyperarid climate remain almost unstudied in this respect. Therefore, we provided the first data on BSCs from a glacier foreland in the E Pamir. These characteristics can be crucial for assessing BSC's role in soil-forming processes in dry, high-altitude periglacial environments. During our research, we assessed (1) BSCs’ morphology and distribution; (2) microbial biomass and nutrient retention patterns in morphologically differentiated BSC types, (3) C, N and P accumulation in BSCs biomass in comparison to sub-crust soils; (4) sub-crust soils enrichment in C, N and P in comparison to bare soils and soils under vascular plants; (5) potential origin and transformation degree of organic matter accumulated by BSCs. Our study showed that the distribution and development of BSCs were noticeably restricted, probably due to low temperatures, aridity and intense periglacial processes, resulting in continuous soil surface remodeling. Thus, poorly developed BSCs were the dominating biologically active soil cover type and, thus, most likely the main biological soil-forming factor in the foreland. BSCs accumulated C, N and P in their biomass and enriched their sub-crust soils in these nutrients. The average enrichment observed for soils under advanced crusts was similar to those obtained for soils under vascular plants. In all types of the studied samples, including bare soils, n-alkanes of vascular plant origin dominated, indicating mixing and uniform distribution of organic matter. Over the course of aridification projected for the Pamir Mountains, the BSCs could potentially become the most important player in the accumulation of soil nutrients in this area. However, due to the dominance of the simplest BSC type, soil formation in the Uisu Glacier foreland will be relatively slow.

Spectral determinants of biological soil crusts in the Gurbantungut Desert

ABSTRACT As thick crustal layers form on dryland surfaces, they affect the spectral information that is originally dominated by sand or rock. The spectral characteristics of organic matter replace the mineral elements as prominent features. In this case, the growth patterns and spectral characteristics of biological soil crusts (BSCs) can be observed. Satellite spectral data have been used for BSC spatial information extraction. However, the dynamic changes in BSCs can affect the spectra. Two aspects are involved here: moisture change and BSC growth. When these changes are superimposed with BSC succession, they lead to an increase in spectral complexity. This study explored three BSC types, including algal crust, lichen and moss, and discussed their spectra. By selecting BSC samples at different succession states and by combining coverage and simulated precipitation, the response of the spectra to BSC coverage and the spectral characteristics of BSCs under dry and wet conditions were measured and analysed. In addition, the spectral index variations caused by coverage and moisture of three types of BSCs were discussed, where the spectral indices include the normalized difference vegetation index (NDVI), brightness index (BI), crust index (CI), and biological soil crust index (BSCI). The results showed that the succession, moisture and growth of BSCs were the main factors affecting their spectra. BSC types can be distinguished in a particular climatic context to determine the degree of BSC succession. Precipitation in the monitoring areas needs to be considered to avoid the effects of dry and wet BSC variations on remote sensing monitoring. The coverage of different types of BSCs in mixed pixels can be determined by multiple indices. The results of this study will provide a basis for monitoring BSCs using satellite spectral information to guide regional ecological management.

Variation of bacterial communities and their driving factors in different types of biological soil crusts in Mu Us sandy land

Variation of bacterial communities and their driving factors in different types of biological soil crusts in Mu Us sandy land

Changes of soil water budget in the area covered by biological soil crusts in Mu Us sandy land, China

Exploring and quantifying the impacts of biological soil crusts on soil hydrological processes and soil water budget in semi-arid ecosystems can provide a theoretical basis for vegetation restoration and reconstruction in deserts. Based on continuous observation of soil water content in different types of areas covered by biological soil crusts (e.g., algae, moss) and bare sand in the Mu Us sandy land during the growing season (May to October) from 2018 to 2020, we examined the effects of biological soil crusts on soil water budget at a depth of 0-40 cm. Results showed that algae and moss crusts significantly reduced soil water supplement below 40 cm by rainfall and increased soil water evaporation loss, compared with that under bare sand. In the relatively wet year (2018), the amount of soil water expenditure (seepage+evaporation) covered by bare sand and the various types of biological soil crusts was less than that of rainfall, resulting in net soil water income. In the relative dry years (2019 and 2020), the amount of soil water expenditure covered by dominant algae and moss crusts was higher than that of rainfall, causing net soil water deficit, but opposite for bare sand. Biological soil crusts led to the imbalance of soil water budget of 0-40 cm depth and even soil water deficit in relatively dry years, which may lead to the succession of plant communities to be dominated by shallow-rooted plants in this area.

Soil nutrients, enzyme activities, and microbial communities differ among biocrust types and soil layers in a degraded karst ecosystem

Being different from the well-known and extensively researched counterparts in arid and semi-arid regions, biological soil crusts (BSCs) in degraded karst ecosystems with subtropical humid climate have been paid little attention. In this study, we investigated the differences of nutrient content, enzyme activity, and microbial communities between different types of BSCs (cyanobacterial crusts, moss crusts, moss-cyanobacteria mixed crusts, and bare soils), and between the BSCs layer and underlying soil. The results showed that the soil nutrient (total nitrogen [TN], total phosphorus [TP], and NH4-N) contents and enzyme activity (urease) in the late-successional stage (moss crusts) were higher than those in early-successional stages (cyanobacterial crusts, moss-cyanobacteria mixed crusts, and bare soils). The species richness of the bacterial community increased with the succession of BSCs, but that of the fungal community did not change. The diversity and composition of both bacterial and fungal communities were not significantly different among biocrust types. The nutrient content (TN, NH4-N), enzyme activity (urease, nitrate reductase, sucrase), and the richness of bacteria and fungi were significantly higher in BSCs layer than in subsurface soils. For either bacteria or fungi, there was a significant difference in community species composition but not in diversity between BSCs layer and subsurface soils. Besides, the results of network topological properties showed that the network structures of both bacteria and fungi in the BSCs layer were more complex than that in the subsurface, and positive links dominated both networks. These results indicate the importance of the BSCs layerespecially moss crusts for nutrient accumulation and microbial genetic resources, and provide an essential basis for further understanding the ecological functions ofBSCsin degraded karst ecosystems with subtropical humid climate.

Differences of bacterial communities in different biological soil crusts around thermal power plant and their influencing factors.

To understand the effects of heavy metal pollution derived from atmospheric dust fall on bacterial community structure under different types of biological soil crusts near mining area, we measured the diversity, community composition, and relative abundance of bacteria communities in three different developmental stages of biological soil crusts (BSCs), including algae (ZB), mixed (HB), and moss (TB) crusts, and control (CK, bare soil) around a typical thermal power plant in Ningdong Energy Industrial Base, using the high-throughput sequencing technique. Environmental factors affecting the bacterial community structure were further investigated. The results showed that there were significant differences in physicochemical properties and heavy metal contents among different BSCs. The BSCs were heavily polluted due to the enrichment of heavy metals from atmospheric dust fall. Among the top ten dominant bacterial phyla, Gemmatimonadetes and Cyanobacteria were significantly distinct among different BSCs. Bacterial α diversity decreased in an order of CK>TB>HB>ZB. The NMDS ordination plots indicated that there were significant differences in the bacteria community composition of the three kinds of BSCs and the CK. The correlation analysis showed that the succession of BSCs significantly affected bacterial community composition in BSCs. Bacterial diversity and composition were closely related to pH, nutrients, and heavy metal contents. The relative abundance of Actinomycetes and Chloroflexi was positively correlated with pH, but negatively correlated with total N, total P, and the contents of heavy metal Pb, Zn, Cd. Results of the redundancy analysis showed that organic carbon, pH, total N, and total P were the major soil factors affecting bacterial α diversity, relative abundance of some dominant phyla, whereas heavy metal contents of Zn, Cd, Pb were the major heavy metals affecting structure of bacterial community which inhibited or stimulated the abundance and diversity of bacterial communities. We concluded that pH, heavy metals, and nutrients were the key factors affecting soil bacteria community composition. The succession of BSCs would improve their physicochemical properties and significantly impacted bacterial community composition. Long term heavy metals enrichment would affect bacterial diversity and community composition of BSCs.

Spatial and temporal distribution of aerobic anoxygenic phototrophic bacteria: key functional groups in biological soil crusts.

Several significant ecosystem services are performed by biological soil crusts (BSCs) in drylands, wherein photoautotrophic microorganisms are commonly critical contributors. However, aerobic anoxygenic phototrophic bacteria (AAnPB) are rarely reported in BSCs, despite being the second major branch of Earth's phototrophic microbes. Here, we collected different types of BSCs and their subsoils from temperate deserts, investigated distributions of AAnPB communities among BSCs using cultivation and high-throughput sequencing approaches, predicted keystone species by co-occurrence network analysis, and verified their effects on BSCs formation through microcosm experiments. The absolute abundances and diversity of AAnPB were higher in BSCs and were closely related with BSCs successional stages, as well as soil organic carbon contents. AAnPB communities in both BSCs and their subsoils were dominated by Proteobacteria and Alphaproteobacteria, specifically Acetobacteraceae, Rhodospirillaceae, Roseiflexaceae, Sphingomonadaceae and Caulobacteraceae families. Mean annual precipitation, pH and available nutrients were the primary factors that shaped AAnPB community structures. The predicted keystone species belonged to the families Acetobacteraceae, Rhodospirillaceae and Sphingomonadanceae. Microcosm experiments demonstrated that inoculation with strains from the three families greatly accelerated the formation and development of BSCs. These observations suggest that AAnPB are likely important functional groups in BSCs that significantly contribute to their formation and important ecosystem services.

Propagación de distintos tipos funcionales de la costra biológica del suelo del desierto del Monte, Argentina

Biological soil crusts (BSC) are associations among cyanobacteria, green algae, lichens, mosses and soil particles, which contribute to multiple ecosystem functions such as nitrogen fixation and soil stabilization. The present work aims to evaluate propagation conditions of different functional types of BSC (dominated by cyanobacteria, cyanolichens, phycolichens and mosses) potentially useful for the recovery of degraded soils. In the greenhouse, different functional types of BSC were cultivated, combining sowing treatments (crushed BSC, discrete fragments) and fertilization (substrate with or without goat manure). Response variables, indicating BSC development and functionality, were total BSC cover, each functional type cover, depth of BSC, soil stability, and ammonium and phosphate concentrations. Total BSC cover increased during the 19 months experimental period. Crushing BSC favored the development and functionality of BSC in pots dominated by cyanolichens, phycolichens and mosses. The addition of fertilizer decreased total BSC cover in pots dominated by phycolichens and mosses. BSC depth and soil stability increased in lichens and moss dominated pots, and were benefited by crushing before sowing. Nutrient concentrations were lower in soils under BSC than in bare soils. We conclude that crushing BSC before sowing and without fertilization favored BSC cover and depth and increased soil stability. These results are useful to plan restoration strategies of degraded drylands.

Biological soil crusts from the Monte desert affect soil moisture and nutrients, and improve Leptochloa crinita grass development

Biological soil crusts (BSC) are widespread in the Monte desert. BSC, by fixing atmospheric N and retaining soil moisture, may enhance grass emergence, growth, and nutritional value. Our aim was to evaluate the effect of different functional types of BSC from the Monte desert on soil moisture and nutrients, N fixation, respiration, grass emergence, growth, and C/N. We sowed Leptochloa crinita seeds in pots with different BSC types (dominated by cyanobacteria, squamulose phycolichens, squamulose cyanolichens, gelatinous cyanolichens, and mosses) under two irrigation treatments: well watered and drought. We determined soil, BSC and grass properties related to nitrogen, phosphorus, and water cycles. In soils under BSC, we determined moisture, nitrate, and phosphate at two depths. In BSC, we determined total N, organic matter, ammonium, respiration, and δ15N. Finally, in grasses growing under BSC, we determined seedling emergence, grass biomass, C/N, and δ15N. All BSC types except cyanobacteria increased soil total N, ammonium, and respiration rates compared to bare soils under drought conditions. Cyanobacteria BSC increased soil moisture under drought conditions, while squamulose phycolichens and mosses increased it under well watered conditions. All BSC types increased underlying soil nitrate under well watered conditions, and decreased phosphate in at least one experimental condition. All BSC types improved at least one grass variable: cyanobacteria decreased C/N; squamulose cyanolichens increased emergence and decreased C/N; squamulose phycolichens increased emergence and biomass; gelatinous cyanolichens decreased C/N; and mosses increased emergence, biomass, and decreased C/N. The differential effects of each BSC type on soil and grass variables, under drought and well watered conditions, suggest the importance of BSC functional diversity on ecosystem functions of water regulation and nutrient cycling.

Ecophysiological Response Against Temperature in Klebsormidium (Streptophyta) Strains Isolated From Biological Soil Crusts of Arctic and Antarctica Indicate Survival During Global Warming

Global warming, as global problem, may particularly affect the vegetation of the Polar Regions. Biological soil crusts (BSCs) as pioneer communities perform a variety of important ecological functions under the harsh environmental conditions at high latitudes. The green algal genus Klebsormidium is a common member of BSCs and in the present study, the ecophysiological resilience to temperature stress of 20 strains from Arctic and Antarctica were investigated. All 20 Klebsormidium strains exhibited the capability to grow under a wide temperature range (from 6 to 28 °C) and hence were characterized as psychrotolerant with optimum growth temperatures between 18 °C and 26 °C. Statistical analyses showed no significant differences in optimum growth temperature. However, growth rates at optimal temperatures varied between strains and indicated infraspecific physiological plasticity. Furthermore, correlation with the sampling sites as well as different BSC types were examined but no significance was confirmed. Our results revealed that Polar Klebsormidium strains are able to survive such changing conditions, and even benefit from higher environmental temperatures.

腾格里沙漠东南缘藻结皮与藓结皮放线菌多样性及其潜在代谢功能

PDF HTML阅读 XML下载 导出引用 引用提醒 腾格里沙漠东南缘藻结皮与藓结皮放线菌多样性及其潜在代谢功能 DOI: 10.5846/stxb201901070055 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目（41661053）；北方民族大学校级一般科研项目（2018XYZSK01） Potential functions of actinobacteria diversity in cyanobacteria and moss crusts in the southeastern Tengger Desert Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:放线菌作为干旱、半干旱环境中生物土壤结皮（Biological Soil Crusts，BSCs）组成的重要生命存在形式之一，不仅是潜在临床有用天然产物化学多样性的重要来源，也是该生态系统物质循环与能量流动的重要参与者。以腾格里沙漠东南缘广泛分布的藻结皮和藓结皮为研究对象，通过宏基因组测序比较分析两种BSCs放线菌种群的分布特征、组成及其潜在代谢功能。结果表明，腾格里沙漠东南缘藻结皮与藓结皮土壤微生物组主要形成以地嗜皮菌属、红色杆菌属、类诺卡氏菌属、游动放线菌属、芽生球菌属、链霉菌属、贫养杆菌属、糖丝菌属、土壤红杆菌属、假诺卡氏菌属、小单孢子菌属、康奈斯氏杆菌属、大理石雕菌属、小月菌属以及弗兰克氏菌属等为主要类群的放线菌群落结构，在两种BSCs类型之间各属分布存在差异。藓结皮中放线菌参与的氨基糖与核苷酸糖代谢、原核生物中的碳固定途径、丁酸代谢、丙酸代谢、丙氨酸/天门冬氨酸和谷氨酸代谢、甲烷代谢、2-羰基羧酸代谢、肽聚糖生物合成、淀粉与蔗糖代谢以及缬氨酸/亮氨酸与异亮氨酸降解显著高于藻结皮。藓结皮中地嗜皮菌属和红色杆菌属对相对丰度前10的代谢功能分类的贡献度显著低于藻结皮，而类诺卡氏菌属、芽生球菌属、贫养杆菌属、游动放线菌属、链霉菌属、假诺卡氏菌属和糖丝菌属等对这些功能的相对贡献在藓结皮中具有重要作用。这些结果可为全面、深入理解腾格里沙漠东南缘藻结皮与藓结皮放线菌资源多样性及其潜在功能多样性提供科学数据，也为理解放线菌在不同类型BSCs中的生态功能提供参考。 Abstract:As one of the significant life forms found in biological soil crusts in arid and semiarid environment, actinomycetes are not only important sources of chemical diversity in natural products that are of potential clinical value but also vital participators in the material cycle and energy flows in the ecological systems. Taking cyanobacteria crusts and moss crusts that are widely distributed in the southeastern Tengger Desert as research objects, metagenome sequencing was performed to compare and analyze the distribution characteristics, components and potential metabolic functions of the actinomycete population in two biological soil crusts. The results showed that the actinomycete community structure of the soil microbiome was mainly composed of the genera Geodermatophilus, Rubrobacter, Nocardioides, Actinoplanes, Blastococcus, Streptomyces, Modestobacter, Saccharothrix, Solirubrobacter, Pseudonocardia, Micromonospora, Conexibacter, Marmoricola, Microlunatus and Frankia. There were differences in the distribution of genera between the two biological soil crust types. The participation of actinomycetes in amino sugar and nucleotide sugar metabolism, glycolysis/gluconeogenesis, carbon fixation pathways of prokaryotes, butanoate metabolism, propanoate metabolism, alanine metabolism, aspartate/glutamate metabolism, methane metabolism, 2-oxocarboxylic acid metabolism, peptidoglycan biosynthesis, starch/sucrose metabolism, and valine/leucine/isoleucine degradation was significantly higher in moss crusts than that in cyanobacteria crusts. However, the contributions of Geodermatophilus and Rubrobacter to the top ten most abundant metabolic functions were obviously lower in moss crusts than that in cyanobacteria crusts. In contrast, the relative contributions of Nocardioides, Blastococcus, Modestobacter, Actinoplanes, Streptomyces, Pseudonocardia, and Saccharothrix to these functions was of great significance in moss crusts. The results provide the scientific data for a comprehensive and in-depth understanding of the diversity of actinomycete resources and potential functions in algae and moss crusts in the southeastern Tengger Desert and for understanding the ecological functions of actinomycetes in different types of biological soil crusts. 参考文献 相似文献 引证文献

腾格里沙漠东南缘不同类型生物土壤结皮对土壤有机碳矿化的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 腾格里沙漠东南缘不同类型生物土壤结皮对土壤有机碳矿化的影响 DOI: 10.5846/stxb201902220317 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目（41671111，41530746） Carbon mineralization of soil covered by different types of biological crusts in the southeastern fringe of the Tengger Desert Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:生物土壤结皮（BSCs）是荒漠生态系统的重要组成部分，是该区土壤碳循环及碳平衡的关键影响因素。研究了腾格里沙漠东南缘不同类型生物土壤结皮覆盖下土壤碳矿化过程及其对温度（10℃、25℃和35℃）和水分（土壤含水量10%和25%）变化响应特征，分析了土壤碳矿化过程与土壤理化性质的关系。结果表明：（1）结皮的形成和发育显著影响土壤有机碳矿化过程，藻类、地衣和藓类结皮覆盖的土壤碳矿化速率和CO2-C累积释放量均显著高于去除结皮的土壤，不同类型BSCs覆盖土壤和去除结皮土壤之间均表现为藓类结皮土壤 > 地衣结皮土壤 > 藻类结皮。（2）含结皮层土壤的平均和最大矿化速率均随温度升高和水分增加而逐渐增大，有结皮覆盖的土壤和去除结皮的土壤对温度和水分变化的响应规律相同。（3）有结皮土壤和去除结皮土壤碳矿化速率的温度敏感性（Q10）与结皮类型密切相关，均表现为藓类结皮 > 地衣结皮 > 藻类结皮。结果表明生物土壤结皮由以藻类为主向以藓类为主的演变进一步促进了土壤碳矿化过程，结皮对土壤碳循环的调控作用受水热等环境因子的共同影响。 Abstract:Biological soil crusts (BSCs) are the association of soil organisms including algea, cyanobacteria, bacteria, fungi, lichen and moss and soil particles, which cover as much as 70% of the interspaces between vegetation and are the key component of arid and semiarid ecosystems. They play a significant role in the process of soil formation and biogeochemical cycling of carbon and nitrogen. Although the functions of BSCs in soil carbon cycling in drylands have been extensively described in the literature, previous research has primarily focused on the effects of BSCs on soil carbon sequestration and respiration. Knowledge is rather poor regarding their effects on soil organic carbon mineralization which is the major part of global carbon cycling and an important process of carbon loss from soils in terrestrial ecosystem. Consequently, understanding the effects of BSCs on soil organic mineralization and their regulating factors is crucial to thoroughly addressing their contribution to the soil carbon budget and balance in drylands.In this study, both intact soil (IS) and BSC-being-removed soil (BRS) samples were collected from algae-, lichen-, and moss-covered soil plots in the southeastern fringe of the Tengger Desert. Carbon mineralization rates of different types of soils and their responses to soil moisture and temperature were investigated by dark incubation. The relationships between soil mineralization rates and soil physicochemical factors were also analyzed. The results showed that (1) SOC mineralization rates and cumulative CO2-C release from IS were significantly higher than those from BRS. These two parameters for both IS and BRS were in the order moss crust > lichen crust > algae crust. (2) The average and maximum soil carbon mineralization rates increased with increasing magnitude of incubation temperature and soil water content, and the dynamic patterns of their response both were similar. (3) Temperature sensitivity (Q10) of the three intact soils and their respective subsoils were closely linked to BSC types, with the highest value for moss-covered soil and the lowest for algae-covered soil. Our understanding of the effects of on soil carbon mineralization suggests that the evolution of BSCs from algae-dominated to moss-dominated soil promoted carbon mineralization, and their regulation of soil carbon cycling was strongly controlled by environmental factors, such as temperature and soil moisture. 参考文献 相似文献 引证文献

Caracterización microtopográfica e influencia de las costras biológicas en la rugosidad del suelo en el centro-oeste de la Argentina

Introducción y objetivos: La influencia de las costras biológicas (CBS) en la rugosidad del suelo es una importante función de estas comunidades a nivel ecosistémico. Nuestros objetivos fueron caracterizar microtopográficamente los tipos de CBS y evaluar su efecto en la rugosidad del suelo en tres sistemas diferenciados por su grado de aridez.
 M&M: El microrelieve de las CBS y su influencia en la rugosidad se evaluaron en tres sistemas: semiárido, árido, e hiperárido; mediante técnicas diferentes y complementarias: método de la cadena, análisis fotográfico y técnica de las varillas metálicas. Para la primera se empleó un diseño en bloque, mientras que paras las otras dos se trabajó sobre los tipos de CBS dominantes en cada sistema.
 Resultados: La morfología de las CBS varió según el tipo de organismo dominante. Los musgos tuvieron una baja altura clasificándose como “suavemente ondulados”, las cianobacterias tuvieronpicos más abruptos, clasificándose como “pinaculadas” y los líquenes tuvieron dos frecuencias de alturas clasificándose como “rodante”. Las CBS influyeron en la rugosidad en los tres sitios evaluados. El sitio hiperárido fue el sitio en el que mayor impacto tuvieron las CBS en la rugosidad. El tipo de CBS que dominó influyó en el nivel de rugosidad hallado.
 Conclusiones: Las variaciones microtopográficas y el incremento en la rugosidad proporcionada por las CBS es clave en la dinámica del Monte debido a que pequeñas interrupciones sobre el terreno podrían incrementar la disponibilidad de agua y disminuir las pérdidas de nutrientes por erosión, dos aspectos fundamentales del funcionamiento de estos sistemas.

Soil ecological stoichiometry characteristics under different types of biological soil crusts in the hilly Loess Plateau region, China

Biological soil crusts (biocrusts) play an important role in soil nutrient accumulation and cycling. We examined the relationship between soil nutrient characters and biocrusts types, with six typical types of biocrusts in the hilly Loess Plateau region, including light cyanobacterial crust, dark cyanobacterial crust, cyanobacterial with moss crust (mixed crusts), moss crust, Diploschistes spp. crust, and Nostoc commune crust. The variations of soil carbon (C), nitrogen (N), phospho-rus (P) concentrations and stoichiometric ratios of biocrustal layer and the subsoil under different types of biocrusts were investigated. The results showed that there were significant differences in C, N, P concentrations and stoichiometric ratio among different biocrusts types. The concentrations and stoichiometric ratios of C, N, P in the biocrustal layer were significantly higher than those of 0-10 cm soil beneath biocrusts. The concentrations of C and N significantly decreased with the increases of soil depth across all the biocrusts types. P content showed no variation between soil layers. The concentrations and stoichiometric ratios of C, N, P of moss crust were significantly higher than those of other biocrusts,with C, N, and P content of 27.07, 2.42 and 0.67 g·kg-1. In soil layer of 0-2 cm, the concentrations and stoichiometric ratios of C, N, P under N. commune crust were significantly higher than those of other biocrusts.

Variation in snow cover drives differences in soil properties and microbial biomass of BSCs in the Gurbantunggut Desert—3 years of snow manipulations

AbstractVariations in snow cover (as specific precipitation) can have an important effect on development of biological soil crusts (BSCs) in arid and semiarid regions, where water is the principal limiting factor for microorganisms. However, there is still limited knowledge available regarding the effects of snowfall on soil properties and microbial biomass in BSCs. To examine these effects of snow cover, three types of BSCs (cyanobacteria‐dominated, lichen‐dominated, and moss‐dominated crusts) were collected and exposed to five snow depths for 3 years. The results indicated that most of the soil properties and soil microbial biomass were significantly (p < .05) affected by 3 years of snow manipulation in three types of BSCs. In BSCs, the values of most soil properties and microbial biomass were higher in the increased snow depth treatments relative the snow removal treatments. Moreover, there were variations in soil properties and microbial biomass among BSC types. In short, increases/decreases in snow cover had different effects on three types of BSCs after 3 years of manipulation. Moreover, increases in snow cover had a positive influence on soil properties and microbial biomass, but negative effects were observed in all BSCs following snow removal and snow reduction. Thus, variations in snow cover can drive differences in soil properties and microbial biomass of BSCs, which may further affect development and succession of BSCs in arid and semiarid regions.

Differences in bacterial community structure between three types of biological soil crusts and soil below crusts from the Gurbantunggut Desert, China

The scarcity of knowledge on differences in the microbial assemblage between biological soil crusts (BSCs) and soil below crusts (SBCs) limits our understanding of the contribution of different layers of topsoil to desert ecosystems. This study used Illumina MiSeq sequencing to determine whether differences in bacterial communities among different types of BSCs (algae, lichen and moss dominated) are greater than those between BSCs and their corresponding underlying soils (0–5 cm) in the Gurbantunggut Desert, China. Alpha and beta diversity of bacterial communities showed that richness and diversity were greater in SBCs than in BSCs, but the absolute bacterial abundance was larger in BSCs than in soils. Differences were mainly in the phyla Cyanobacteria, Actinobacteria, Chloroflexi and Acidobacteria. Cyanobacteria were concentrated in BSCs, especially in algae‐dominated BSCs. The relative abundances of Actinobacteria, Chloroflexi and Acidobacteria in SBCs were more than twice those in BSCs, and they were also abundant in the lichen‐ and moss‐dominant crusts. The number of sample‐specific genera was larger in BSCs, but there were more shared genera among SBCs. These results, combined with the principal coordinate analysis and the predicted function profiles, showed that differences in microbial community structure and function in desert ecosystems were greatest between BSCs and the underlying soils, followed by differences among the three types of BSCs, and differences were smallest between the soils below different crusts. These differences might be closely related to the soil chemical properties, especially to pH and fertility. Our study indicated that microbial communities tended to converge in SBCs of different microhabitats.Highlights We studied bacterial community composition in different types of BSCs and SBCs. Differences in bacterial community were greatest between BSCs and SBCs. BSC components contributed to small‐scale microbial heterogeneity in SBCs. Surface soil bacterial communities were strongly stratified even at the centimetre scale from BSCs.

Photoautotrophic organisms control microbial abundance, diversity, and physiology in different types of biological soil crusts

Biological soil crusts (biocrusts) cover about 12% of the Earth’s land masses, thereby providing ecosystem services and affecting biogeochemical fluxes on a global scale. They comprise photoautotrophic cyanobacteria, algae, lichens and mosses, which grow together with heterotrophic microorganisms, forming a model system to study facilitative interactions and assembly principles in natural communities. Biocrusts can be classified into cyanobacteria-, lichen-, and bryophyte-dominated types, which reflect stages of ecological succession. In this study, we examined whether these categories include a shift in heterotrophic communities and whether this may be linked to altered physiological properties. We analyzed the microbial community composition by means of qPCR and high-throughput amplicon sequencing and utilized flux measurements to investigate their physiological properties. Our results revealed that once 16S and 18S rRNA gene copy numbers increase, fungi become more predominant and alpha diversity increases with progressing succession. Bacterial communities differed significantly between biocrust types with a shift from more generalized to specialized organisms along succession. CO2 gas exchange measurements revealed large respiration rates of late successional crusts being significantly higher than those of initial biocrusts, and different successional stages showed distinct NO and HONO emission patterns. Thus, our study suggests that the photoautotrophic organisms facilitate specific microbial communities, which themselves strongly influence the overall physiological properties of biocrusts and hence local to global nutrient cycles.

生物土壤结皮碳释放对水热因子的响应

在室内控制条件下，以腾格里沙漠东南缘1964年人工固沙植被区藻类、混生和藓类结皮为对象，研究了3个温度梯度(15℃、25℃和35℃)和7个水分梯度(3%、5%、10%、15%、20%、25%和30%质量含水量)条件下其碳释放特征。在相同水分条件下，BSCs和流沙呼吸速率随着温度的增加而增加，35℃时BSCs和流沙呼吸速率达到最大值。藓类结皮的呼吸速率显著高于其他土壤类型土壤呼吸。藓类结皮Q10为1.40~3.17，藻类结皮为0.81~3.07，混生结皮为0.55~3.84，流沙为1.19~2.16。BSCs类型、水分和温度显著影响BSCs碳释放量(P < 0.001)。水分含量较高的条件下，藻类和混生结皮的呼吸速率受到了明显抑制，而对藓类结皮的呼吸速率影响不显著。 The carbon release of different types of biological soil crusts (BSC) covered soil was measured under different temperatures condition (15˚C, 25˚C and 35˚C) and different soil water content conditions (3%, 5%, 10%, 15%, 20%, 25% and 30%) in fixed sand dunes at the re-vegetated area in Tengger Desert, Northern China. In the same soil water content condition, the carbon release rate of BSCs and sand were increased with temperature increasing, the highest carbon release rate occurred at 35˚C. The carbon release rate of moss crust was significantly higher than other soil types. Q10 value of moss crust was 1.40 - 3.17, algae crust was 0.81 - 3.07, mixed crust was 0.55 - 3.84 and sand was 1.19 - 2.16. BSCs types, soil water content and temperature were significantly affected on carbon release rate (P < 0.001). The results showed that the respiration rate of the algal crust and mixed crust were significantly restrained by higher soil water content; however, moss crust was not significantly influenced.