Search Results (69)

Marine fog is a key non-rainfall water source that sustains microbial activity and transports dissolved nutrients inland, influencing early soil development in hyperarid ecosystems. However, the mechanisms through which sustained fog inputs drive soil surface modification and biocrust formation remain poorly understood. This study evaluated the effects of long-term fog augmentation on soil surface development, biocrust dynamics, and associated microbial communities in the Atacama Desert. We implemented a four-year fog addition field experiment with three sampling times (T0, T24, T48) to assess changes in soil physicochemical properties, biocrust composition, and the integrated multi-diversity of archaea, bacteria, fungi and protist. Sustained fog input transformed bare soils into biological soil crusts, particularly lichen- and moss-dominated stages. This transition was accompanied by increases in soil nitrogen, variations in organic matter accumulation, a shift from alkaline to near-neutral pH, and improvements in soil stability and water retention. Multi-diversity increased over time and was positively associated with ecosystem variables linked to water availability, structural stabilization, and decomposition. These functions, integrated into an ecosystem multifunctionality index, also increased under prolonged fog input, revealing a positive relationship between multifunctionality and multi-diversity. Overall, the results demonstrate that sustained fog input strongly enhances early soil surface development and biocrust establishment, highlighting the ecological importance of marine fog in shaping biodiversity and ecosystem functioning in hyperarid landscapes. Full article

Arctic biological soil crusts (biocrusts) are known to host diverse fungal communities that facilitate nutrient cycling and soil stabilisation in these harsh environments. In this study, the diversity and composition of fungi were assessed across elevation and spatial gradients in biocrusts from Kongsfjorden (Svalbard) using metagenomic sequencing. Within the observed fungal phyla, Ascomycota was dominant across all sites, with Basidiomycota and Rozellomycota also exhibiting high abundances. Furthermore, saprotrophic fungi were most abundant, followed by mycorrhizal and parasitic guilds. Lichen-associated fungi were also detected across the samples, although their read counts were substantially lower. Additionally, the fungal genus richness and guild composition exhibited no significant variation between elevations, but location within the fjord strongly shaped community structure. Full article

Examining the changing patterns and underlying mechanisms of soil biomass carbon stocks constitutes a fundamental aspect of soil biology. Despite the potential influence of the sulfur cycle and the life strategies of organisms on community biomass, these factors have rarely been studied in tandem. Biocrusts are model systems for studying soil ecosystems. In this study, metagenomic analysis of biocrusts related to different life strategies from five batches over four consecutive years demonstrated that, in free-living communities, microbial biomass carbon (MBC) synthesis, via assimilatory sulfate reduction (ASR), is primarily coupled with the 3-hydroxypropionate/4-hydroxybutyrate and Calvin–Benson–Bassham cycles. These pathways are affected by the oxidation-reduction potential (Eh), pH, electrical conductivity, and nutrient levels. The decomposition of organic carbon (OC) via dissimilatory sulfate reduction (DSR) was accompanied by the production of dimethyl sulfide (DMS), which was influenced by the C/S ratio and moisture, whereas the synthesis of MBC by symbiotic communities was found to be affected by Eh and pH, and decomposition was affected by the C/S ratio. The MBC stock was influenced by all strategies, with resource strategies having the greatest impacts during the growing season, and the contribution of chemotrophic energy was most significant in free-living communities. In conclusion, the MBC in biocrusts is associated with both ASR and DSR and is facilitated by the A-, S-, and P-strategies under the regulation of the stoichiometric C/S ratio. The exploration of microbial life strategies and sulfur cycling in biocrusts within arid ecosystems in this study offers a new perspective on the patterns of change in soil biomass carbon stocks. Full article

This study investigates the long-term effects of catastrophic phosphate mining effluent contamination on the biocrust microbial community structure in sections of the ephemeral Ashalim Stream, Negev Desert, Israel. Microbial communities were characterized using next-generation sequencing of 16S rRNA gene fragments, conducted 1.5 and 5 years after the contamination event, across five stream strips. Samples from the nearby, uncontaminated Gmalim Stream served as controls. Biocrusts from Ashalim showed higher relative abundances of the phyla Actinobacteria and Firmicutes compared to Gmalim, whereas Chloroflexi were more prevalent in the controls. At the genus level, Blastococcus, Bacillus, Massilia, and Noviherbaspirillum were more abundant in the Ashalim strips, while Flavisolibacter, Segetibacter, and Rhodocytophaga were more abundant in the controls. Notably, genera within the Cyanobacteria phylum accounted for only 0.0–2.0% of sequences in Ashalim samples versus 2.5–20% in controls. The filamentous Leptolyngbya, Tychonema, and Trichocoleus genera were the most dominant cyanobacteria in all samples. The Nitrogen-fixing cyanobacterial genera Scytonema and Nostoc were consistently detected in Gmalim, but only in trace numbers in certain Ashalim sites. The results from both sampling campaigns support the hypothesis that phosphate effluent contamination had a profound impact on biocrust microbial community structure and function. In particular, the marked reduction in Cyanobacteria suggests a long-lasting disruption that may substantially hinder the natural ecosystem rehabilitation. Full article

Most traits of assimilative branches (ABs) present large spatial and interspecific differences; however, it is still unclear how small-scale soil heterogeneity influences nutrient traits in ABs under the same climatic conditions. The AB samples of Ephedra przewalskii (EP; small-sized), Calligonum mongolicum (CM; medium-sized), and Haloxylon persicum (HP; large-sized), as well as soil samples, were collected at three sites (north, middle, and south; within 65 km) in the southeastern Gurbantunggut Desert, China. The interspecific and inter-site differences in C:N:P:K stoichiometry and the relationships with soil properties were discussed. From north to south, soil nutrients and biocrust development improved, whereas coarse sand proportion decreased. Species and site markedly influenced ABs’ stoichiometry, with a significant interaction. At the species level, each stoichiometric trait differed among species. CM exhibited the lowest C:P and N:P, whereas HP had the highest N:P. At the site level, N:P and C:P of EP and CM increased from north to south, whereas HP changed unclearly. CM and HP had higher N–P scaling exponents, EP and CM exhibited a higher K allocation rate, resulting in the co-limitation of N and P for all species. The overall stoichiometric homeostasis ranked as follows: HP > CM > EP. The three shrubs were dispersed among each other in an ordination diagram based on nutrient metrics, with different distribution patterns. The nutrient traits in the ABs of EP and CM, rather than HP, were markedly correlated with most soil factors. Local-scale soil variation indeed influenced the nutrient strategies of desert shrubs; plant size might be another important factor. Full article

The evaluation of bioavailable forms of heavy metals in zones of anthropogenic pollution is the basis of ecological risk assessment. The characterization of the consequences of the operation of the Pechenganikel smelting plant was carried out using AAS and two methods of soil bioavailable forms of heavy metal extraction (3% nitric acid and ammonium acetate buffer with pH 4.8) along three directions from the plant, corresponding to the wind prevalence. Buffer extraction provided more significant correlations between Ni, Co, Cu, Pb, and Zn, compared to nitric acid application, indicating a negative correlation between soil Cu, Co, and the distance from the plant, while no significant correlations were recorded for nitric acid extracts. A higher significant correlation number arose between soil elements in buffer extracts along the N-E direction than the S-W one. In the former direction, the number of the mentioned correlations decreased according to the following sequence: Zn (6) > Cu (5) > Se and Co (4) > Ni and Fe (3); in nitric acid extract, only significant correlations of Cu, Zn, and Se with Co and Ni were recorded. Biocrust formation was revealed only along the N-E direction, characterized by unexpected high Se concentrations and intensive correlation between Zn and all the elements extracted by the buffer. Biocrust accumulated high levels of all the elements tested and showed antioxidant activity and polyphenol content significantly correlated with soil organic matter. The biocrust mineral content demonstrated a complex relationship with soil Fe, Cu (buffer extract), and Se, as well as Co and Zn (nitric acid extract). Application of linear mixed-effects modelling and transfer factor analysis indicate that biocrusts may serve as effective bioindicators of both absolute metal contamination and its bioavailable fractions. The results indicate the expediency of using both methods of soil extraction for assessing the ecological risk and soil–biocrust relationships. Full article

This study investigated how moss species identity and coverage density influence soil organic carbon (OC), total nitrogen (TN), total phosphorus (TP), cation exchange capacity (CEC), and stoichiometric ratios (C/N, C/P, N/P ratios) across soil depths in karst ecosystems of northern Guangxi, China. Spectral responses to moss cover were concurrently analyzed. Soil properties under moss crusts and bare controls were quantified through chemical assays. Coverage effects were compared via bar charts (sparse) and point-line plots (dense) with fitted curves and 95% confidence intervals. Spectral reflectance (250–2500 nm) was measured to characterize surface optical properties. Statistical correlations between variables were established. Research has shown the following: (1) Moss coverage significantly enhanced OC, TN, and CEC versus bare soil (B. dichotomum showed the strongest improvement: dense crust increased OC/TN/TP by 6.37/1.73/0.45 g kg⁻¹ and doubled CEC). (2) All nutrients and CEC decreased with depth, most sharply for G. humillimum OC (22.38% reduction at 3–6 cm) and P. yokohamae CEC (9.97% reduction). (3) Stoichiometric ratios exhibited species-specific responses: B. dichotomum had the smallest inter-layer differences in C/N/P ratios, while G. humillimum increased C/N by 34.33% at 3–6 cm. Sparse coverage elevated N/P ratios up to 59.38% (G. humillimum, 0–3 cm). (4) Spectral analysis revealed the following: Sparse coverage boosted reflectance via edge scattering and soil background contributions. Dense coverage suppressed reflectance due to water absorption (1450/1900 nm) and limited scattering. Bare soil exhibited persistently low reflectance from hematite absorption (500–700 nm). Moss biocrusts—particularly dense B. dichotomum—optimize topsoil fertility and CEC in karst soils, though effects diminish sharply below 3 cm. Spectral signatures provide non-invasive indicators of coverage density and erosion resistance. These insights highlight the crucial role of species-specific moss selection in promoting sustainable restoration practices and long-term ecological recovery in rocky desertification regions. Full article

The polar environment is one of the most extreme environments of our world. However, even in the cold deserts of Antarctica, life thrives, often in the form of biocrusts (biological soil crusts)—complex communities consisting of hundreds of organisms. The reaction to abiotic stress in members of these communities is often inferred from laboratory experiments on isolated species and single factors, without taking into consideration any mitigation effects by the communities or complex habitats. In this study, we aimed to infer the stress situation of the filamentous green alga Klebsormidium in Antarctic biocrusts in situ using metatranscriptomic data. Klebsormidium is ubiquitous in biocrusts and well studied with respect to abiotic factors, allowing the comparison of lab experiments with the in situ situation. In this study, we identified Klebsormidium flaccidum to be present in biocrusts from Livingston Island (Antarctica). Metatranscriptomic data for the biocrust were used to investigate the presence of cold and desiccation stress in situ. To this end, we identified consistently expressed and stress-regulated genes in published stress transcriptomes of Klebsormidium that could serve as markers for environmental stress levels. These “marker genes” were used to construct marker gene indices to assess stress states in biocrusts by comparing transcript expression ratios under different conditions—a novel framework for the assessment of microbial community responses to environmental stressors. However, many potential marker genes behaved quite differently in the laboratory and in the natural environment. In the end, rather than relying on indices based on individual marker genes, comparing the expression levels of whole stressor-regulated gene sets proved to be a more reliable approach to examining stress in situ. This study highlights the potential of marker genes for broader ecological and environmental monitoring using metatranscriptomic data. Full article

The surface of the Great Wall harbors a large number of non-vascular plants dominated by cyanobacteria, lichens and mosses as well as microorganisms, and form biocrusts by cementing with the soils and greatly alters the pore structure of the soil and the ecohydrological processes associated with the soil pore space, and thus influences the soil resistance to erosion. However, the microscopic role of the biocrusts in influencing the pore structure of the surface of the Great Wall is not clear. This study chose the Warring States Qin Great Wall in Weiyuan, Gansu Province, China, as research site to quantify thepore structure characteristics of the three-dimensional of bare soil, cyanobacterial-lichen crusts, and moss crusts at the depth of 0–50 mm, by using optical microscopy, scanning electron microscopy, and X-ray computed tomography and image analysis, and the precipitation infiltration process. The results showed that the moss crust layer was dominated by large pores with long extension and good connectivity, which provided preferential seepage channels for precipitation infiltration, while the connectivity between the cyanobacterial-lichen crust voids was poor; The porosity of the cyanobacterial-lichen crust and the moss crust was 500% and 903.27% higher than that of the bare soil, respectively. The porosity of the subsurface layer of cyanobacterial-lichen crust and moss crust was significantly lower than that of the biocrusts layer by 92.54% and 97.96%, respectively, and the porosity of the moss crust was significantly higher than that of the cyanobacterial-lichen crust in the same layer; Cyanobacterial-lichen crusts increased the degree of anisotropy, mean tortuosity, moss crust reduced the degree of anisotropy, mean tortuosity. Biocrusts increased the fractal dimension and Euler number of pores. Compared with bare soil, moss crust and cyanobacterial-lichen crust increased the isolated porosity by 2555% and 4085%, respectively; Biocrusts increased the complexity of the pore network models; The initial infiltration rate, stable infiltration rate, average infiltration rate, and the total amount of infiltration of moss crusted soil was 2.26 and 3.12 times, 1.07 and 1.63 times, respectively, higher than that of the cyanobacterial-lichen crusts and the bare soil, by 1.53 and 2.33 times, and 1.13 and 2.08 times, respectively; CT porosity and clay content are significantly positively correlated with initial soil infiltration rate (|r| ≥ 0.85), while soil type and organic matter content are negatively correlated with initial soil infiltration rate. The soil type and bulk density are directly positively and negatively correlated with CT porosity, respectively (|r| ≥ 0.52). There is a significant negative correlation between soil clay content and porosity (|r| = 0.15, p < 0.001). Biocrusts alter the erosion resistance of rammed earth walls by affecting the soil microstructure of the earth’s great wall, altering precipitation infiltration, and promoting vascular plant colonisation, which in turn alters the erosion resistance of the wall. The research results have important reference for the development of disposal plans for biocrusts on the surface of archaeological sites. Full article

Soil degradation has been accelerating globally due to climate change, which threatens food production, biodiversity, and ecosystem balance. Traditional soil restoration strategies are often expensive, slow, or unsustainable in the long term. In this context, cyanobacteria have emerged as promising biotechnological alternatives, being the only prokaryotes capable of performing oxygenic photosynthesis. Moreover, they can capture atmospheric carbon and nitrogen, release exopolysaccharides (EPSs) that stabilize the soil, and facilitate the development of biological soil crusts (biocrusts). In recent years, the convergence of multi-omics tools, such as metagenomics, metatranscriptomics, and metabolomics, has advanced our understanding of cyanobacterial dynamics, their metabolic potential, and symbiotic interactions with microbial consortia, as exemplified by the cyanosphere of Microcoleus vaginatus. In addition, recent advances in bioinformatics have enabled high-resolution taxonomic and functional profiling of environmental samples, facilitating the identification and prediction of resilient microorganisms suited to challenging degraded soils. These tools also allow for the prediction of biosynthetic gene clusters and the detection of prophages or cyanophages within microbiomes, offering a novel approach to enhance carbon sequestration in dry and nutrient-poor soils. This review synthesizes the latest findings and proposes a roadmap for the translation of molecular-level knowledge into scalable biotechnological strategies for soil restoration. We discuss approaches ranging from the use of native biocrust strains to the exploration of cyanophages with the potential to enhance cyanobacterial photosynthetic activity. By bridging ecological functions with cutting-edge omics technologies, this study highlights the critical role of cyanobacteria as a nature-based solution for climate-smart soil management in degraded and arid ecosystems. Full article

Biological soil crusts (referred to as biocrusts) constitute prominent components within the ecosystem of tropical coral islands in the South China Sea, covering approximately 6.25% of the island’s terrestrial surface. Biocrusts are the key to the restoration of the island ecosystem. It is widely acknowledged that phototrophic microorganisms profoundly contribute to biocrust formation and development. They provide fixed carbon and nitrogen and produce exopolysaccharides for the BSC ecosystems. Although aerobic anoxygenic phototrophic bacteria (AAPB) are an important functional group of phototrophic microorganisms, the community characteristics of AAPB in coral island biocrusts and their role in the formation of biocrusts have rarely been reported. In this study, we employed amplifications of the pufM gene to characterize the AAPB communities of biocrusts on a tropical coral island. The outcomes revealed a discernible augmentation in both the abundance and richness of AAPB concurrent with the formation of biocrusts, concomitantly with a decrement in diversity. Within the AAPB communities, the Pseudomonadota (Proteobacteria) phylum emerges as the prevailing dominion, indicating marked differentiations in terms of family and genus compositions between the biocrust and bare soil. Canonical correlation analysis has unveiled a robust and meaningful correlation between the AAPB composition and the attributes of the soil, including total nitrogen, total organic carbon, total phosphorus, pH, and calcium content. Furthermore, co-occurrence network patterns shift with biocrust formation, enhancing stability. Meanwhile, keystone taxa analysis revealed specific OTUs associated with each soil type, with genus Brevundimonas as the main group. Furthermore, pure-culture AAPB strains isolated from biocrusts exhibited a panorama of diversity, predominantly belonging to Pseudomonadota. Particularly, the Skermanella and Erythrobacter genera demonstrated strong exopolysaccharide secretion and sand-binding capabilities. This study sheds light on the significant functional role of AAPB in tropical coral island biocrusts, expanding our understanding of their contribution to ecosystem services, and providing valuable insights for ecological restoration efforts on coral islands. Full article

Rocky outcrops are harsh habitats that support specialized organisms and communities, including biocrusts, which play roles in soil stabilization, water retention, and nutrient cycling. Despite their importance, tropical biocrusts, particularly in granite-gneiss formations, remain underexplored. This study examines biocrust composition in a granite-gneiss outcrop in a rural landscape in Southeastern Brazil, identifying microhabitats and analyzing co-occurrence patterns and community structure. We recorded eleven bryophyte species and one diatom species, while six cyanobacteria, three charophytes, and two chlorophytes were identified at the genus level. They were found in shallow depressions, though termite mounds also served as an important microhabitat. The cyanobacterium Scytonema was the most prevalent taxon. The liverwort Riccia weinionis had the highest number of positive co-occurrences, associating with cyanobacteria and algae. Network analysis based on co-occurrence revealed that Scytonema and the mosses Anomobryum conicum and Bryum argenteum were the most connected taxa, crucial for ecological network stability. The moss Bryum atenense acted as a key intermediary, with the highest betweenness centrality—a measure of its role in linking taxa. These findings provide insights into tropical rocky outcrop biocrusts, shedding light on their composition and interactions. Furthermore, the co-occurrence patterns and key taxa connectivity uncovered provide insights into ecosystem stability and can guide ecological restoration strategies. Full article

In drylands, microalgae dwelling in the biocrust are inevitably confronted with nitrogen deficiency and desiccation stress, despite the protection afforded by the soil biological complex. However, the environmental adaptive features and mechanisms of these microalgae remain largely unknown. In this study, we explored the adaptive changes of a biocrust-derived unicellular microalga, Vischeria sp. WL1 (Eustigmatophyceae), in the face of long-term nitrogen deficiency. Attention was focused on the alterations in cell wall properties and the associated desiccation resistance. After exposure to long-term nitrogen deficiency, the cell walls of Vischeria sp. WL1 thickened substantially, accompanied by enhanced rigidity and an improvement in desiccation resistance. In contrast, Vischeria sp. WL1 cells cultivated under nitrogen-replete conditions were highly vulnerable to desiccation stress. Additional cell wall alterations after nitrogen starvation included distinct surface sculpturing, variations in monosaccharide composition, and changes in functional groups. Collectively, this study provides valuable insights into the survival strategies of biocrust-derived microalgae in nitrogen-deficient dryland environments. Full article

Soil erosion is a serious environmental problem that leads to land degradation and ecological imbalance, thereby eliciting extensive and profound worldwide concern. Biological soil crusts (biocrusts) play a crucial role in soil stabilization; however, the underlying microbial enzymatic mechanisms remain poorly understood. The present study aimed to characterize carbonatogenic bacteria and investigate the role of their carbonic anhydrase-induced carbonate crystals in promoting soil shear strength within biocrusts. The results demonstrated a significant increase in the activity of carbonic anhydrase during biocrust formation and development (p < 0.05). A total of 35 strains exhibiting carbonic anhydrase activity were isolated from biocrusts, belonging to Actinomycetota, Bacillota, Pseudomonadota and Cyanobacteriota. The subsequent investigation revealed a positive correlation between the carbonic anhydrase activities of the strains and the shear strength during sand consolidation. Specifically, strain SCSIO19859, a type of cyanophyta, exhibited the highest carbonic anhydrase activity, of 1.50 U/mL. It produced 0.70 g/day of calcium carbonate and demonstrated a shear strength that was 6.09 times greater than that of the control group after sand consolidation for seven days of incubation under optimal conditions. X-ray diffraction and scanning electron microscope analysis revealed that SCSIO19859 produced calcite and vaterite carbonates, which significantly increased the shear strength of the sand grains (p < 0.05). This study provides evidence for the ecological function of biocrusts in promoting soil erosion resistance from the perspective of carbonatogenic bacteria-derived carbonic anhydrase. The functional strains with carbonic anhydrase obtained from this study have significant potential applications in enhancing soil erosion resistance. Full article

Biological soil crusts are important components of dryland ecosystems, showing variations in appearance, morphology, and function across developmental stages. However, the methods for recording biocrust developmental stages have not been simplified and standardized. In this study, three developmental grades for both cyanobacterial crust and moss crust were defined based on visual indicators such as color, thickness, and moss height. A field survey was conducted across three precipitation regions in northern China, during which the developmental grades of cyanobacterial and moss crusts were visually recorded. Key biocrust developmental indicators, including shear strength, penetration resistance, coverage, chlorophyll a content, and bulk density were measured for each grade. The results showed that both cyanobacterial and moss crusts could be effectively classified into three developmental grades based on these indicators, with a 90% concordance between the measured indicators and the defined grading method. This finding validated that the method could accurately reflect biocrust developmental stages while simplifying field recordings. Developmental indicators in various grades of cyanobacterial and moss crusts showed a moderate (30% < CV < 100%) to strong (CV > 100%) variation, highlighting the importance of environmental heterogeneity at the regional scale. Moreover, the grading method proved effective across varying spatial scales, highlighting its broad applicability. However, its validation across the comprehensiveness of target objects and the geographical scope remains limited. Future research should focus on expanding the grading method to include lichen crust, refining it across diverse ecosystems, and exploring the integration of advanced technologies such as hyperspectral imaging and machine learning to automate and improve the classification process. This study provides a simple and effective grading method for visually recording the developmental stages of biological soil crusts, which is useful for ecological research and field applications. Full article