Biological Soil Crust Communities Research Articles

Dam construction accelerated the development of biological soil crusts in degraded soil patches in the Lhasa River basin, Qinghai-Tibetan Plateau

The Lhasa River Basin currently faces severe land degradation. In recent years, several dams have been built on the main stream, whereas, their impact on land desertification remains less elucidated. Herein, we investigated variances of soil properties and microbial communities in biological soil crusts (BSCs) along the valley area of Lhasa River and the mountain slope (altitude gradient) in reservoir area after five years of dam construction. Soil nutrient and water contents, enzyme activities, and N-cycle related functional gene copies significantly increased in reservoir-affected areas and decreased with the increase of mountain slope altitude and the distance away from the reservoir, which were usually degraded soil patches; similarly, the relative abundance of bacteria, fungi and moss in BSCs significantly increased in reservoir-affected areas, whilst that of cyanobacteria was higher in degraded soil patches. The linear and structural equation models also showed that dam construction altered water distribution status of soil surface, which enhanced soil properties, N-cycle and increased the relative abundance of moss of BSCs, and successfully accelerated the development and succession of BSCs in degraded soil. This study firstly reported that dam construction could accelerate the succession process of degraded soil in the reservoir affected area and thus a reference for ecological restoration of desertification soil of the Lhasa River Basin in QTP.

Successional development of the phototrophic community in biological soil crusts, along with soil formation on Holocene deposits at the Baltic Sea coast

Harsh environmental conditions form habitats colonized by specialized primary microbial colonizers, e.g., biological soil crusts (biocrusts). These cryptogamic communities are well studied in drylands but much less in temperate coastal dunes, where they play a crucial role in ecological functions. Following two dune chronosequences, this study highlights the successional development of the biocrust’s community composition on the Baltic Sea coast. A vegetation survey, followed by morphological species determination, was conducted. Sediment/soil cores of the different dune types were analyzed to uncover the potential impacts of the biocrust community on initial soil formation processes, with special emphasis on biogeochemical phosphorous (P) transformations. Biocrust succession was characterized by a dune type-specific community composition, shifting from thinner algae-dominated biocrusts in dynamic dunes to more stable moss-dominated biocrusts in mature dunes. The change in the biocrust community structure was accompanied by an increase in Chl a, water, and organic matter content. In total, 25 algal and cyanobacterial species, 16 mosses, and 26 lichens across all sampling sites were determined. The pedological characterization of these cores elucidated initial processes of soil genesis, such as decalcification, acidification, and the accumulation of organic matter with dune and biocrust development. Furthermore, the chemistry of iron (Fe)-containing compounds such as the Fedithionite/Fetotal ratios confirmed mineral weathering and the beginning of soil profile development. The biocrusts accumulated P over time, while the P content in the underlying sediment did not change. That implies that biocrusts take up P from the geological parent material in the dunes, thereby accumulating available P in the ecosystem, which gets transferred into subsoil horizons through leaching or redeposition. The relative proportion of the bioavailable P pool (56% to 74% of Pt) increased with dune succession. That happened at the expense of more stable bound P, which was transformed into labile P. Thus, the level of plant available P along the dune chronosequences increased due to the microbial activity of the biocrust organisms. It can be concluded that biocrusts of temperate coastal dunes play a crucial role in maintaining their habitat by accumulating nutrients and organic matter, supporting soil development and subsequent vegetation.

Bacterial community in biological soil crusts from a Brazilian semiarid region under desertification process

Bacterial community in biological soil crusts from a Brazilian semiarid region under desertification process

Distinguishing natural and anthropogenic contributions to biological soil crust distribution in China's drylands

Desertification caused by natural factors and human activities seriously threatens dryland biological communities. However, the impact of these factors on non-vascular plants in drylands has not been fully documented. This study proposed a framework to distinguish the natural and anthropogenic contributions to the distribution of the biological soil crust (BSC) coverage. The 20 model-simulated environmental datasets, including climate, soil characteristics and terrain, were selected to explore the internal relationship between these environmental drivers and BSC coverage. Random forest classification and regression models were developed to calculate the BSC coverage in the drylands of China under natural conditions. By subtracting the predicted natural BSC coverage from the observed BSC coverage, the spatial distribution of changes in BSC coverage attributed to human activities was mapped. The results showed that in the limited vegetation areas of China's drylands, human activities had a positive impact on BSC coverage in only 11.3 % of the regions while having a negative effect on 25.4 % of the regions. Moreover, human activities led to a 33 % reduction in BSC coverage in these regions. The positive impacts of large-scale ecological restoration projects on BSC coverage in the drylands of China were limited due to land use changes caused by human economic activities. This framework provides support for assessing regional variations in anthropogenic impacts on dryland BSC communities and contributes to the development of appropriate dryland management policies.

Bacterial and plant community successional pathways in glacier forefields of the Western Himalaya

Glacier chronosequences offer a unique opportunity to observe primary successional patterns and assess the interaction between biological communities and abiotic conditions. Bacteria are one of the first organisms to colonize such ecosystems, yet factors determining their distribution and diversity are still in need of understanding. In this study, we investigated the associated abiotic and biotic factors related to bacterial communities across post-glacial moraines at two localities in the Ladakh region of the Western Himalaya which differed in elevation and climate. By measuring soil chemistry, plant, biological soil crust, and bacterial community composition while accounting for moraine age and topography, we reveal the successional paths of multiple trophic levels at the highest elevation glacier forefields known to be studied. Biological soil crust communities followed a trajectory of being dominated by the order Chroococcales before transitioning to filamentous Nostocales and Oscillatoriales and eventually decreasing in cover as plants colonize the area. Using variation partitioning, we found bacterial communities in the higher locality, Tso Moriri (5800 m), were more associated with soil conditions, while at the lower location, Nubra (5150–5400 m), bacterial communities were more coupled with plant community composition. Furthermore, using generalized linear models, bacterial family richness was found to be significantly correlated with plant species richness, however, topography was also significant, indicating geomorphological depressions or gullies at the bottom of moraines potentially harbor higher bacterial richness prior to the advanced colonization of plants. These results suggest the community structure and successional pathways of bacteria and plants in glacier forefields are influenced by differing biotic and abiotic factors at different geographical locations and provides a local framework for the future of deglaciated environments.

Diversity of Cyanobacteria and Algae in Biological Soil Crusts of the Northern Ural Mountain Region Assessed through Morphological and Metabarcoding Approaches

In mountain regions, biological soil crusts (BSCs) provide essential ecological services by being involved in primary production and nitrogen fixation. Eukaryotic algae and cyanobacteria are important photosynthetic components of these unique cryptogamic communities. Here, we present an overview of the eukaryotic and prokaryotic diversity of such phototrophs in BSCs in the mountain tundra of the northern Ural Mountains. Such assessment is based on morphological surveys and the first metabarcoding analysis in the region. In total, 166 taxa of Cyanobacteria and 256 eukaryotic algae (including Euglenophyta, Ochrophyta, Dinophyta, Bacillariophyta, Chlorophyta, and Charophyta) were identified. For the first time, 86 taxa new to the BSCs of the high-mountain belt of the region were discovered. Considering species composition, Cyanobacteria and Chlorophyta are the most abundant taxa in all the analyzed BSCs. The genera Nostoc, Coccomyxa, Chlamydomonas, Leptolyngbya, Stenomitos, Pycnacronema, Stigonema, and Eunotia had the highest number of taxonomic units. These groups shape the structure, function, and ecology of the BSC communities in the studied region. Our results show that BSCs in the tundras of the Ural Mountains have a high active and passive biodiversity of terrestrial cyanobacteria and algae. Both implemented methods resulted in similar results with a comparable number of algae and cyanobacteria species per sample. Metabarcoding could be implemented in future in the region to accurately screen photosynthetic organisms in BSCs.

Habitat-specific environmental factors regulate the spatial variability of biological soil crust microbial communities on the Qinghai-Tibet Plateau

Biological soil crusts (BSCs) are an important biological component of the soil surface, covering approximately 12 % of the Earth's land surface. Although BSCs are closely related to habitats, the microbial diversity and spatial variability of BSCs in different ecosystems are still unclear, especially on the Qinghai-Tibet Plateau (QTP), where climate is changeable and habitats are complex. Here, we investigated the diversity, assembly processes, spatial distribution pattern and driving factors of prokaryotic and eukaryotic microbial communities in BSCs in four habitats on the QTP. It was found that habitat-specific environmental factors regulated the composition, diversity and spatial variability of BSC microbial communities. Soil organic carbon and soil water content were the most important factors (R2 = 0.9024, P = 0.001; R2 = 0.8004, P = 0.001) affecting the spatial differences in prokaryotes and eukaryotes, respectively. Under the specific climate of the QTP, the spatial pattern of microbial communities in BSCs was controlled by precipitation rather than temperature. In addition, ecological processes further explained the effects of habitat specificity, and environmental filtering explained microbial community differences better than dispersal limitation. The results of the neutral community model and the normalized stochastic ratio index revealed that the assembly of prokaryotic communities was determined by deterministic processes at the regional scale, and at the local scale, the assembly process was mainly determined by habitat type, while the assembly of eukaryotic communities was determined by stochastic processes at both the regional and local scales. This study provided a scientific reference for the prediction of BSC distribution and resource conservation under future climate change scenarios.

Soil organic carbon changed by grazing determinates the abundance, diversity and composition of aerobic methanotroph communities in cyanobacteria-dominated biological soil crusts in desert steppes

Aerobic methanotrophic bacteria (AMB) are widely present in biological soil crusts (BSCs) and are important methane-oxidizing groups in desert ecosystems. Grazing disturbance can destroy BSCs, but how it affects AMB is unclear. In this study, the AMB in BSCs under no-, moderate- and heavy-grazing intensities and continuous grazing for 10 years were studied using high-throughput sequencing technology and bioinformatics analysis. The results showed that soil total organic carbon (TOC), dissolved organic carbon (DOC), available phosphorus, and leucine aminopeptidase significantly reduced, while nitrate and ammonium nitrogen and β-1,4-acetylglucosaminidase enzyme activities increased, with increasing grazing intensity. The AMB were highly diverse, with an absolute abundance from 2.97 to 4.95 × 105 (in no and heavy grazing treatments, respectively). Grazing disturbance especially influenced the relative abundance of AMB communities at the genus level. Members belonging to Methylocystis, Methylosinus, and Methylobacter were the top three genera and core methanotrophs in AMB communities, and closely related to the stability of AMB community networks under grazing disturbance. AMB community structure were majorly affected by TOC and DOC. We provide novel insights into grazing could change the soil organic matter, which determinates the abundance, diversity and composition of AMB communities in cyanobacteria-dominated BSCs in desert steppes.

Characterization of a novel polyextremotolerant fungus, Exophiala viscosa, with insights into its melanin regulation and ecological niche.

Black yeasts are polyextremotolerant fungi that contain high amounts of melanin in their cell wall and maintain a primar yeast form. These fungi grow in xeric, nutrient depletes environments which implies that they require highly flexible metabolisms and have been suggested to contain the ability to form lichen-like mutualisms with nearby algae and bacteria. However, the exact ecological niche and interactions between these fungi and their surrounding community are not well understood. We have isolated 2 novel black yeasts from the genus Exophiala that were recovered from dryland biological soil crusts. Despite notable differences in colony and cellular morphology, both fungi appear to be members of the same species, which has been named Exophiala viscosa (i.e. E. viscosa JF 03-3 Goopy and E. viscosa JF 03-4F Slimy). A combination of whole genome sequencing, phenotypic experiments, and melanin regulation experiments have been performed on these isolates to fully characterize these fungi and help decipher their fundamental niche within the biological soil crust consortium. Our results reveal that E. viscosa is capable of utilizing a wide variety of carbon and nitrogen sources potentially derived from symbiotic microbes, can withstand many forms of abiotic stresses, and excretes melanin which can potentially provide ultraviolet resistance to the biological soil crust community. Besides the identification of a novel species within the genus Exophiala, our study also provides new insight into the regulation of melanin production in polyextremotolerant fungi.

Changes of bacterial community structure,monosaccharide composition and CO2 exchange along the successional stages ofbiological soil crusts.

Biological soil crusts (BSCs) are a dominantecological landscape of drylands, which have asignificant impact on global biogeochemical flux. However, it is unclear how bacterial community and physiological characteristics vary along the BSCssuccessional stages. In this study, bacterial community composition, physiological characteristics, and monosaccharide composition of extracellular polysaccharides (EPSs)were compared among different successional stages. Our findings demonstrated that besidesthe dominant bacterial species, the bacterial communities also showed considerable differences between these two stages. Cyanobacteria were keystone taxain the early stage, while heterotrophic bacteria (Proteobacteria, Actinobacteria and Acidobacteria) were keystone taxa in the later stages. According to the results ofCO2 exchange, cyanobacterial crusts accumulated net carbon faster than moss crusts, whilemoss crusts had a significantly higher respiration rate. The monosaccharide analysis indicated that the EPSs components also varied depending on BSCs' successional stages. Specifically, the contents of rhamnose and arabinose were higher in thecyanobacterial cruststhan other types of crusts, while the contents of fucose, xylose, mannose and glucose were the highest in cyanobacterial-lichen crusts, andgalactose contentwas highest inthe moss crusts. Altogether, our results stress the heterogeneous variation of BSCs along with succession, andthis work offered a fresh viewpoint for a deeper comprehension of the interactions between the monosaccharide components of EPS and the networks of bacterial communities in BSCs.

Functional significance of microbial diversity in arid soils: biological soil crusts and nitrogen fixation as a model system.

Microbial communities respond to changes in environmental conditions; however, how compositional shifts affect ecosystem processes is still not well-understood and it is often assumed that different microbial communities will function equally under similar environmental conditions. We evaluated this assumption of functional redundancy using biological soil crusts (BSCs) from two arid ecosystems in Mexico with contrasting climate conditions (hot and cold deserts) following an experimental approach both in the field (reciprocal transplants) and in laboratory conditions (common garden), focusing on the community's composition and potential for nitrogen fixation. Potential of nitrogen fixation was assessed through the acetylene reduction assay. Community composition and diversity was determined with T-RFLPs of nifH gene, high throughput sequencing of 16S rRNA gene amplicons and metagenomic libraries. BSCs tended to show higher potential nitrogen fixation rates when experiencing temperatures more similar to their native environment. Moreover, changes in potential nitrogen fixation, taxonomic and functional community composition, and diversity often depended on an interactive effect of origin of the communities and the environment they experienced. We interpret our results as legacy effects that result from ecological specialization of the BSC communities to their native environment. Overall, we present evidence of nonfunctional redundancy of BSCs in terms of nitrogen fixation.

Successional Development of the Phototrophic Community in Biological Soil Crusts on Coastal and Inland Dunes.

(1) Biological soil crusts (biocrusts) are microecosystems consisting of prokaryotic and eukaryotic microorganisms growing on the topsoil. This study aims to characterize changes in the community structure of biocrust phototrophic organisms along a dune chronosequence in the Baltic Sea compared to an inland dune in northern Germany. (2) A vegetation survey followed by species determination and sediment analyses were conducted. (3) The results highlight a varying phototrophic community composition within the biocrusts regarding the different successional stages of the dunes. At both study sites, a shift from algae-dominated to lichen- and moss-dominated biocrusts in later successional dune types was observed. The algae community of both study sites shared 50% of the identified species while the moss and lichen community shared less than 15%. This indicates a more generalized occurrence of the algal taxa along both chronosequences. The mosses and lichens showed a habitat-specific species community. Moreover, an increase in the organic matter and moisture content with advanced biocrust development was detected. The enrichment of carbon, nitrogen, and phosphorus in the different biocrust types showed a similar relationship. (4) This relation can be explained by biomass growth and potential nutrient mobilization by the microorganisms. Hence, the observed biocrust development potentially enhanced soil formation and contributed to nutrient accumulation.

Spatial self-segregation of pioneer cyanobacterial species drives microbiome organization in biocrusts

Microbial communities are typically characterized by some degree of self-organization. In biological soil crust (biocrust) communities, vertical organization of resident populations at the mm scale is driven by organismal adaptations to physicochemical microniches. However, the extent of horizontal organization and its driving processes are unknown. Using a combination of observational and genetic mapping, we provide evidence for a highly defined, horizontal self-organization (patchiness) at the mm to cm scale in a successionally early biocrust community dominated by the pioneer cyanobacteria, Microcoleus vaginatus (Microcoleaceae) and Parifilum sp. (Coleofasciculaceae). Experiments with representative isolates of each species demonstrate that the phenomenon is driven by active spatial segregation based on cross-species sensing through the exometabolome acted upon with motility responses. Further, we show that both species share the ability to enrich for specialized cyanospheres of heterotrophic bacteria at smaller scales, and that these cyanospheres are characterized by compositional host-specificity, thus expanding the reach of spatial patchiness beyond primary producers. Our results highlight the importance of specific microbial interactions in the emergence of microbiome compositional architecture and the enhancement of microbial diversity.

Facilitating restoration of degraded biological soil crusts using mixed culture inoculation

In arid and semiarid ecosystems, the biological soil crust (biocrust) community is ecologically critical and it is advantageous to restore damaged biocrust. Coastal sage scrub (CSS) is a unique and imperiled valuable habitat. At present, studies of biocrust restoration in CSS habitat do not exist. This study examined the feasibility of isolating and culturing a mix of endemic CSS cyanobacteria and green algae to inoculate native CSS soil, thereby facilitating recovery of disturbed biocrust. To gauge whether inoculation increases soil function, we measured culture growth, chlorophyll a, extractable polysaccharides, and stability. Growth of biocrust organisms and increases in functionality were compared among three inoculation treatments (mixed culture, ground biocrust, and uninoculated control) with either autoclaved or non-autoclaved native soil to determine the extent that native crust organisms can regrow without inoculation. A novel genus and species of cyanobacteria was isolated and classified as Trichotorquatus maritimus. The mixed culture included a green alga, possibly Chlamydomonas callunae. Mixed inoculum added to non-autoclaved native soil significantly improved the soil functions. After two months, the mixed inoculum increased chlorophyll levels, soil stability, and increased extractable polysaccharides. It may be possible in the future to restore biocrust in CSS using mixed culture inoculation.

Early successional changes in biological soil crust community assembly and nutrient capture in mining impacted landscapes

Biological soil crusts (BSCs) are communities of bryophytes, lichens, bacteria, and fungi and are the primary colonizing communities in early successional landscapes. In early ecosystem development BSCs often improve the physical and chemical conditions while also promoting soil microbial communities. Although BSCs are considered ecosystem engineers in many early successional environments, the links between BSC functional processes and their developmental stage are unclear, especially in landscapes recovering from anthropogenic disturbances. In this study we examined natural BSC development over a 30-year chronosequence on two mining impacted landscapes in both boreal and arctic regions of Canada. Using High Throughput Sequencing (HTS), we found similar ubiquitous ruderal bryophytes and bacteria species common at both study areas, but significant differences in lichen and fungal community structure between the two locations. In addition, community assembly of BSC macro (bryophytes and lichens) and micro (bacteria and fungi)-phyla changed over the first 30 years of recovery at both mine sites, however, these changes were unique to each study location. We observed nutrient accumulation in the crust layer but did not find clear trends in available nutrients or gas flux over time. Instead, changes in our functional measurements were associated with colonization by specific BSC species. Further, the bacterial community at both mines seemed to be responding to changes in the bryophyte communities as they developed over time. This suggests that the establishment of bryophyte communities in early succession may be driving micro-phyla BSC community composition. A holistic view of BSCs as they develop over time in relation to their functional abilities needs further investigation, and this study provides insight into these interactions. This knowledge will improve both our understanding of early stage BSC development and our ability to develop restoration techniques to effectively restore landscapes disturbed by anthropogenic activities.

The Effects of Biochar on Microbial Community Composition in and Beneath Biological Soil Crusts in a Pinus massoniana Lamb. Plantation

Biological soil crusts (BSCs) hold promise for reducing soil erosion in subtropical forest plantations, and microorganisms profoundly affect the formation and development of BSCs. The effects of biochar as a soil conditioner on the diversity and structure of soil microbial communities in BSCs are largely unknown. Therefore, our aim was to determine how biochar might improve microbial community composition and BSC function. Herein, a field experiment was conducted in a P. massoniana plantation; the addition of biochar was the treatment, and no biochar addition was the control (CK). Soil microbial communities associated with moss BSCs (in and beneath BSCs) with and without the addition of biochar were analyzed by Illumina sequencing technology. The results showed that Acidobacteria (28.35%), Proteobacteria (22.53%), Actinobacteria (17.41%), and Chloroflexi (16.74%) were the dominant bacterial phyla, whereas Basidiomycota (70.00%) and Ascomycota (22.76%) were the dominant fungal phyla in BSCs. The soil bacterial and fungal OTU number and richness in BSCs were higher than those beneath BSCs. The relative abundances of Acidobacteria, Chloroflexi, and Basidiomycota were higher in BSCs than beneath BSCs, whereas the relative abundances of Actinobacteria, Firmicutes, Ascomycota, and Chytridiomycota showed the opposite trend. Beneath BSCs, biochar addition increased the soil bacterial OTU number and richness (ACE index and Chao1) but decreased the soil fungal OTU number and richness. Biochar had little effect on soil microbial community structures in BSCs; however, beneath BSCs, it significantly increased the relative abundances of Acidobacteria, Chloroflexi, and Basidiomycota and significantly decreased the relative abundances of Actinobacteria, Firmicutes, Ascomycota, and Chytridiomycota. Biochar-induced changes in soil microbial communities were related to soil environmental factors, especially urease activity, organic matter content, pH, total nitrogen content, and sucrase activity. We demonstrated the different effects of biochar on soil microbial communities in and beneath the BSCs of subtropical forest plantations; these findings provided new insights into soil stabilization with BSCs below the forest canopy in subtropical regions.

Microhabitat-specific differences on the composition and function of biological soil crust communities

Microhabitat-specific differences on the composition and function of biological soil crust communities

Ability of soil bacterial composition as an indicator of levels of soil erosion in a badland

Calanchi (plural of calanco) are typical Italian badlands created by a combination of morphogenetic processes (rill and interrill erosion, gullying, piping, and mass movements) mainly originated by the effect of water. Calanchi are characterized by the sparse and patchy distribution of vegetation, and, in interplant areas, the soil surface is colonized by an association of organisms known as biological soil crust (BSC). A morphometric analysis of 45 basins in the studied calanchi area, based on a high-resolution digital elevation model, showed those basins are sediment removal systems characterized by rapid and relevant erosion processes. The goal of the current research is to evaluate the bacterial composition of BSC and to recognize its signature of land degradation processes in soil samples by a microbiological analysis (culture-dependent and culture-independent approaches). Soil bacterial distribution was investigated by a culture-independent approach, applying Illumina technology in soils with different vegetation cover. Four species were detected in site A (bare soil). In sites B (sparse vegetation) and C (densely vegetated soil) 19 and 18 bacterial taxa were detected, respectively. Sites B and C were characterized by 17 species in common. The microbial communities detected at sites B and C are typical of environments unable to support vegetation and microorganisms that are not specialized to live in these environments. Biodiversity analysis of the bacterial communities of biocrusts, done using richness and evenness indices, confirmed that the composition of the BSC communities can be a signature of the intensity of soil erosion processes.

Mapping biological soil crusts in a Hawaiian dryland

ABSTRACT Historical and ongoing land use patterns in the Hawaiian Islands have degraded the Islands’ drylands, causing erosion and detrimentally affecting adjacent coastal marine ecosystems. Biological soil crust (biocrust) communities have been shown to increase soil stability in drylands worldwide, but their efficacy in mitigating soil erosion in Hawaiian drylands is largely unknown. Using a combination of field data and imagery collected by small unmanned aerial systems (sUAS), we mapped biocrusts and examined their influence on soil stability in the Kawaihae watershed, an erosion-prone dryland on leeward Hawai`i Island. We created classified maps of biocrust cover from imagery collected at three spatial resolutions (1.2, 2.1 and 2.8 cm/pixel) using the pixel-based Support Vector Machine (SVM) classifier and investigated the impacts of spatial resolution and biocrust level of development on classification accuracy. Our medium (2.1 cm) resolution image produced the highest overall classification accuracy when biocrust was treated as a single class (82.1%). We explored the spatial impacts of biocrusts on soil loss via sUAS-derived measurements of elevation change over a four-year time span. We found differences in soil loss among land cover types, but robustly quantifying these was a challenge, as much of the change fell below statistically significant limits of detection. We investigated the relationship between biocrust development and soil stability by conducting soil aggregate stability testing at the three biocrust levels of development (LODs) present at the study site. We found a significant increase in soil stability from soils without surface biocrusts (LOD score of 0) to those with biocrusts at any development level (LOD 1–3). Our research adds to the body of biocrust knowledge by presenting new information about biocrust distribution and soil stabilization capabilities in Hawaiian drylands. We also provide insights into the trade-offs between spatial resolution and classification accuracy for biocrust classification and land cover analysis.

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.