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Soil erosion is a significant environmental issue worldwide, particularly in island regions where land resources are exceedingly scarce. Biological soil crusts play a crucial role in mitigating soil erosion, yet the precise effect and mechanism of biological soil crusts against erosion remain ambiguous. In this study, biological soil crusts at various developmental stages from a tropical coral island in the South China Sea were chosen to investigate the role of carbonic anhydrase in mitigating erosion. A cohesive strength meter, real-time quantitative PCR, and 16S rRNA gene high-throughput sequencing were employed to assess variations in soil antiscouribility as well as bacterial abundance and composition during the formation and development of biological soil crusts. Scanning electron microscopy was utilized to detect carbonates induced by bacterial carbonic anhydrase and elucidate their role in the solidification of sand particles. The findings indicate that the formation and development of biological soil crusts significantly enhance anti-scouribility. Comparison to those of bare coral sand, the shear stress increased from 0.35 to 1.11 N/m2 in the dark biocrusts. Moreover, significantly elevated carbonic anhydrase activity was observed in biological soil crusts, demonstrating a positive correlation with antiscouribility. In addition, there was a significant increase in bacterial abundance within the biological soil crusts. The enrichment of Cyanobacteriales and Chloroflexales potentially contributed to the increased carbonic anhydrase activity and antiscouribility. Furthermore, three cyanobacterial strains with carbonic anhydrase activity were isolated from biological soil crusts and subsequently confirmed to enhance sand solidification through microbial carbonate precipitation. This study presents initial evidence for the role of microbial carbonic anhydrase in enhancing the antiscouribility of biological soil crusts during their formation and development. These findings offer novel insights into the functional and mechanistic dimensions underlying the mitigation of soil erosion facilitated by biological soil crusts, which are valuable for implementing sustainable biorestoration and environmental management technologies to prevent soil erosion. [Display omitted] • Antiscourability and carbonic anhydrase activity enhanced during the formation and development of biological soil crusts. • Antiscourability was positive correlated with carbonic anhydrase activity. • Cyanobacteriales and Chloroflexales contribute to the augmentation of carbonic anhydrase activity. • Carbonic anhydrase-induced carbonates enhanced soil shear strength in biological soil crusts. [ABSTRACT FROM AUTHOR]

Biocrusts are soil surface assemblages of lichens, bacteria, fungi, and bryophytes that support key ecosystem processes in alpine environments. Their role in carbon and nitrogen cycling is critical to soil pedogenesis. Establishment of biocrusts after disturbance events is an important first step in restoring ecosystem function. However, our understanding of active restoration of alpine biocrusts, as well as how environmental factors affect ecosystem processes associated with early succession, is poor. In a field experiment at two alpine sites (a xeric and a mesic site), we monitored microclimatic conditions and assessed function of mature biocrusts. We also examined the influence of inoculation with mature biocrusts and fertilization on the recovery of biocrusts in disturbed alpine soils. Biocrust cover and soil surface nitrogen fixation were enhanced by inoculation after 12 weeks at the mesic site. However, at the xeric site biocrust cover increased while nitrogen fixation declined. Restoration of dry and cold alpine environments presents many challenges and recovery of ecosystem services may require additional restoration techniques and longer timelines. Improved understanding of the community composition of alpine biocrusts and their developmental trajectories over time will assist with effectively using biocrusts to promote recovery of ecosystem processes in disturbed alpine environments. [ABSTRACT FROM AUTHOR]

With the continuing consumption of resources and increasingly prominent environmental issues, microalgal resource utilization has received extensive attention. In this study, based on the microalgal investigation in desert biological soil crusts (BSCs) using pyrosequencing technology, the cultivated crust microalgae were further isolated in order to obtain high quality microalgae for resource utilization. The results showed that with crust development and succession, microalgal diversity gradually decreased, including the number of operational taxonomic units (OTUs) and genus, although Microcoleus always was the dominant genera. Pyrosequencing obtained 630 OTUs of cyanobacteria, 25 OTUs of green algae and 9 OTUs of diatom; however, part of cultivated microalgae still could not yet be detected due to the DNA extraction preferences and errors caused by PCR amplification. After isolation, four strains were purified and cultivated, including two filamentous cyanobacteria Microcoleus vaginatus BSC-06 and Scytonema javanicum BSC-39, and two unicellular green algae Chlorella sp. BSC-24 and Monoraphidium dybowskii BSC-81. The two green algae grew fast (>250 mg L -1  d -1 ), and achieved high lipid productivity up to 75–85 mg L -1  d -1 , with lipid content of 28.7–39.0%, thus was considered as promising feedstock for biodiesel production. In addition, the two crust cyanobacteria could be used to construct artificial cyanobacterial soil crusts in desertification control, although their biomass accumulation was not as high as that in the green algae. Ultimately, combining biodiesel production with desertification control would not only improve desert environments, but also provide ideal places for the local microalgal resource exploitation, further promoting desert socioeconomic development. [ABSTRACT FROM AUTHOR]

Biological Soil Crusts (BSCs) represent an important part of the living cover in drylands worldwide. BCSs change soil hydrology due to extracellular polymeric substances (EPS)-excreting species of cyanobacteria, dominant members of dryland-BSCs. The presence of EPS allowed matric potential (Ψ m ) to remain unchanged down to 20% water content, whereas, without EPS, Ψ m started decreasing at 80% water content. The EPS matrix improved the water retaining capacity of soil, suggesting that BSCs would delay onset of restrictive matric potential values due to its larger water holding capacity. [ABSTRACT FROM AUTHOR]

• High amounts of non-rainfall water (10%–15% of water input) occur in the alpine sandy land. • Biological soil crusts increase the daily mean non-rainfall water amount by 23%–30%. • Biological soil crusts enhance non-rainfall water accumulation and dissipation rates by >20%. • The effects of soil crusts can be attributed to changes in soil physicochemical properties. • The principal source of non-rainfall water is atmospheric vapor (∼60%). Non-rainfall water originating from atmospheric and soil vapors is a major water source that supports dryland ecosystem functioning. The alpine sandy land ecosystem is fragile, where biological soil crusts develop widely on the soil surface and play a critical role in regulating surface hydrological processes. Yet, the effects of biological soil crusts on non-rainfall water in the alpine sandy land remain unclear. Therefore, we investigated the patterns and main sources of non-rainfall water under different biological soil crusts in the Qinghai–Tibet Plateau region during the growing season (May–September 2017). Micro-lysimeters were used to measure the amount of non-rainfall water in surface soil (0–10 cm) covered with moss and algae crusts in an interdune area. The results revealed that non-rainfall water occurred for at least 12 h·d−1 (7 p.m.–7 a.m.) and disappeared for 5 h (7 a.m.–12 a.m.). The daily mean non-rainfall water amount ranged between 0.324 and 0.426 mm. Differences in the physical and chemical properties of surface soil caused by biological soil crusts affected the accumulation and dissipation of non-rainfall water. The accumulation and dissipation rates of non-rainfall water under biological soil crusts were respectively 1.22–1.32-fold (F = 8.01, P < 0.05) and 1.21–1.27-fold (F = 8.86, P < 0.05) higher than those of bare sand. Biological soil crusts also increased the amount of total non-rainfall water by 23.41%–30.39% (F = 5.367, P < 0.05), accounting for 2.4%–3.0% of the total water input. Atmospheric vapor condensation was the principal source of non-rainfall water (>60%). Nevertheless, biological soil crusts increased both atmospheric and soil vapor condensation by 29.44%–39.98% (F = 12.45, P < 0.05) and 13.09–13.94% (F = 5.91, P < 0.05), respectively. Although non-rainfall water contributed only 10%–15% of the total water input, it constituted a main water input to the ecosystem during the dry period of less rainfall (up to 20%, 19.72 vs. 95.72 mm). In conclusion, non-rainfall water, especially atmospheric vapor condensation, makes a non-negligible contribution to water input in the alpine sandy land ecosystem, for which biological soil crusts enhance the role of non-rainfall water in the water input in surface soil water balance dynamics. [ABSTRACT FROM AUTHOR]

• The removal of biocrusts from bare patches reduced R s (soil respiration) by 15 %. • The removal of biocrusts from shrub patches increased R s by 57 %. • The discrepancy in R s after biocrust removal attributed to the root distribution. • The removal of biocrusts of two patches altered the sensitivity of R s to soil moisture. • Destroying biocrusts in shrub patches have a greater impact on the carbon balance. The important role of biological soil crusts (biocrusts) in determining the soil carbon balance in dryland ecosystems under future climate change has been widely explored. However, when assessing the effects of biocrusts on soil respiration, few studies have considered biocrusts in bare soil patches and shrub soil patches. A field experiment was performed with five simulated rainfall addition events (0, 5, 15, 25, and 40 mm) in shrub and bare soil patches in June (early growing season, EGS), July (middle growing season, MGS) and September (late growing season, LGS) in 2016 and 2017. Our objective was to examine whether biocrusts at shrub and bare soil patches have the same effect on soil respiration under altered rainfall regimes. The results showed that the removal of biocrusts from bare patches reduced soil respiration by 15 % after rainfall amounts of 5–40 mm and increased the subsurface soil temperature and decreased the soil moisture after various rainfall treatments. However, in shrub patches, the removal of biocrusts led to a significant increase in soil respiration of 57 % and subsequent increases in subsurface soil temperature and moisutre. The discrepancy in the soil respiration response between the two types of patches might be attributable to the increase in soil infiltration after biocrust removal, with a greater stimulating increase in soil carbon emissions stimulated in the shrub patches than in the bare patches due to more the greater amounts of roots distributed under the former shrub patches. Our results indicate that the destruction of biocrusts in shrub patches may reduce the ability of biocrust ecosystems to become a net carbon sinks, with potentially negative consequences for ecosystem function and sustainability in water-limited regions. [ABSTRACT FROM AUTHOR]

The Soil Crust International (SCIN) project was a multidisciplinary attempt to obtain a complete understanding of biocrusts communities across Europe, including among the monitored locations the Tabernas badlands in Spain, the driest habitat in the whole continent. Here we provide an overview in a Mini-Review format of our research about the functional performance of the more relevant biocrust forming organisms involved, looking for similarities and differences in the behavior of these communities in regions with contrasting environmental conditions, allowing a deeper understanding of habitat over biocrusts functioning. New unpublished results linked to SCIN are also included in order to reinforce or clarify some general ideas proposed within the text. The general perspective provided to the data through this unique multi-site comparison, will allow in depth studies of relevant functional traits that can shed some light over the possibility of biocrusts behaving as functional types under some circumstances. Poikilohydry is proposed as an essential driving force involved, at different extents, in all key traits ruling biocrusts ecophysiology. • Summary of biocruts functional performance across Europe. • Functional Type theory has been approached to biocrusts ecophysiology. • The environment is a regulator of several key functional traits in biocrusts. • Poikilohydry acts as a driving force in biocrusts functionality. [ABSTRACT FROM AUTHOR]

• Induced biocrust growth varied between slope aspect, steepness and plant cover. • Slope aspect affect biocrust development and soil properties significantly. • Soil factors affected by microhabitats influence biocrust distribution. Cyanobacterial inoculation can accelerate the formation of induced biological soil crusts (IBSCs) and is suggested as an effective strategy for desertification reversal. However, previous studies concerning the spatial distribution of IBSCs at the micro scale are insufficient. In this study, IBSCs distributed in microhabitats differing in slope aspect, slope gradient and plant cover were investigated to reveal the effects of microhabitats on soil properties and IBSC development. There are significant differences in soil environmental factors including microclimates and soil physical properties, and soil component factors including SOC, TN, TP and dissolved organic matter components among sites with different microhabitats. Compared with IBSCs on south-facing slopes and in interspaces, those under plant cover and on north-facing slopes were characterized by higher biomass and moss abundance, indicating later successional stages. The relative contributions of microhabitat characteristics to the variance in environmental conditions and soil properties were slope aspect (59.5%) > shrub cover (13.8%) > slope gradient (6.2%). Furthermore, these environmental and soil component factors contributed equally and interactively to IBSC development. Our findings reveal that soil environmental factors and soil composition affected by microhabitats drive the distinct development of IBSCs in interactive and essential ways. More attention should be paid to these microhabitat-related soil factors in the IBSC rehabilitation and maintenance engineering. [ABSTRACT FROM AUTHOR]

Biological soil crusts (biocrusts) are generally found in many landscapes. Biocrusts are known to have a key role in terms of soil stabilization but the mechanism of biocrusts is poorly understood. Thus, this work intends to examine the impact of two biocrusts: Cyanobacteria and Chlorophyte , on parameters of cohesive soil erodibility (erodibility coefficient, k d , and critical shear stress, τ c) using a small-scale form of Jet Erosion Test (mini-JET) at different drying times. In addition, the study aims to develop relationships between τ c and k d versus certain soil characteristics. Eighteen undisturbed soil samples of two biocrust types Cyanobacteria , and Chlorophyte , and bare soils were acquired from the banks of the Tigris River in Iraq, and were tested in a laboratory using a mini-JET at drying times of 5, 8, and 12 days, in order to mimic field conditions. It was observed that dead algae still adhered to and bound soil particles together throughout the observation period, which contributed to soil stability, and increased moisture and nutrient retention before decomposition. As the drying times increased in the two biocrusts, the statistical results showed a reduction in k d , while τ c values increased. The k d decreased as salt concentration, organic matter, and calcium carbonate increased, while the τ c increased. No change in pH levels of soil was observed due to the reactions in the biocrusts between the algal crust and soil particles, which increased organic matter and calcium carbonate. This study discusses the benefits of using a JET instrument; including reducing testing time, conserving energy, and providing low-cost method for observation of crusted soil stabilization, in comparison with previous techniques. [ABSTRACT FROM AUTHOR]

The microbiota in three distinct terrestrial habitats (biological soil crusts – BSC, crust-adhering soil beneath BSC – trans, and crust-free soil close to BSC – soil) was studied in 33 temperate forest stands differing in management intensity (ForMI). Specific lipid fractions and respective marker fatty acids were used to determine microbial biomass and community structure (phospholipid fatty acids – PLFA), energy reserves (neutral lipid fatty acids – NLFA), and community level lipid profiles (CLLP) of nematodes and enchytraeids. The density and diversity of nematode fauna were additionally determined morphologically. The highest total amounts of PLFA and NLFA occurred in the BSC, followed by soil and trans habitats, indicating stronger effects of habitats than forest management intensity. This corresponds to the distribution pattern of bacterial PLFA that dominated the soil microbiota. The highest nematode population density occurred in the BSC, followed by soil and trans. The BSC was dominated by bacterial feeders and omnivores, while plant feeding nematodes were most frequent in the crust-free soil habitat. The highest biomass of photoautotrophs also occurred in the BSC, followed by the crust-adhering and crust-free soil habitats. Redundancy analysis indicated strong effect of ForMI and total N on soil PFLAs and NFLAs across habitats. The C:N and C:S ratios were important for the separation of NLFAs while P:S accounted for the separation of PLFAs. Bacterial and fungal PLFAs largely separated the microbial community across habitats, and particularly between BSC and trans habitats. The separation of nematodes and enchytraeids by CLLP was less pronounced, and most distinct between the crust-free soil and BSC or crust-adhering soil habitats. Overall, BSC and crust-adhering soil habitats provide different suitability for microbiota, resulting in specifically adapted communities that are shaped by the management intensity and nutrient availability. • Forest management intensity shape biological soil crust with different microhabitats. • Greater effect of habitats on soil microbiota than forest management intensity. • Bacterial and fungal PLFAs separated microbial communities across habitats. • High nematode density in crust, dominated by omnivores and bacteria feeders. [ABSTRACT FROM AUTHOR]