Successful lichen translocation on disturbed gypsum areas: A test with adhesives to promote the recovery of biological soil crusts

Co-inoculation of fungi and desert cyanobacteria facilitates biological soil crust formation and soil fertility

The inoculation of cyanobacteria for enriching soil nutrients and forming biological soil crusts (BSCs) is considered an effective means to restore degraded soil. However, there are limited studies on the application of co-inoculation of fungi and cyanobacteria for degraded soil remediation. In this study, a high exopolysaccharide-secreting fungi Zh2 was isolated from lichen BSCs in Hobq Desert, and co-inoculated with a cyanobacterial strain identified as Phormidium tenue in different proportions to form BSCs on sand during a 35 days incubation period. Results revealed significant differences in crust biomass and soil properties among crusts with different cyanobacterial/fungal inoculation ratios. Microbial biomass, soil nutrient content and enzyme activities in crusts co-inoculated with cyanobacteria and fungi were higher than those inoculated with cyanobacteria and fungi alone. The inoculation of cyanobacteria contributed to the fulvic-like accumulation, and the inoculated fungi significantly increased the humic-like content and soil humification. Redundancy analysis showed that the inoculation of cyanobacteria was positively correlated with the activities of urease and phosphatase, and the content of fulvic-like. Meanwhile, the inoculation of fungi was positively correlated with the contents of total carbon, total nitrogen and humic-like, the activities of catalase and sucrase. Cyanobacteria and fungi play distinct roles in improving soil fertility and accumulating dissolved organic matter. This study provides new insights into the effects of cyanobacteria and fungi inoculations on the formation and development of cyanobacterial-fungus complex crusts, offering a novel method for accelerating induced crust formation on the surface of sand.

Spontaneous Primary Succession and Vascular Plant Recovery in the Iberian Gypsum Quarries: Insights for Ecological Restoration in an EU Priority Habitat

Gypsum covers a vast area of the Iberian Peninsula, making Spain a leader in its production. Gypsum is a fundamental raw material for modern societies. However, gypsum quarries have an obvious impact on the landscape and biodiversity. Gypsum outcrops host a high percentage of endemic plants and unique vegetation, considered a priority by the EU. Restoring gypsum areas after mining is a key strategy to prevent biodiversity loss. For the implementation of restoration approaches, understanding vegetation's successional processes can be of invaluable help. To fully document the spontaneous succession in gypsum quarries and to evaluate its interest for restoration, 10 permanent plots of 20 × 50 m were proposed, with nested subplots, in which vegetation change was recorded for 13 years in Almeria (Spain). Through Species-Area Relationships (SARs), these plots' floristic changes were monitored and compared to others in which an active restoration was carried out, as well as others with natural vegetation. Furthermore, the successional pattern found was compared to those recorded in 28 quarries distributed throughout the Spanish territory. The results show that an ecological pattern of spontaneous primary auto-succession is widely recurring in Iberian gypsum quarries, which is capable of regenerating the pre-existing natural vegetation.

Chronicle of Research into Lichen-Associated Bacteria

Lichens are mutually symbiotic systems consisting of fungal and algal symbionts. While diverse lichen-forming fungal species are known, limited species of algae form lichens. Plasticity in the combination of fungal and algal species with different eco-physiological properties may contribute to the worldwide distribution of lichens, even in extreme habitats. Lichens have been studied systematically for more than 200 years; however, plasticity in fungal-algal/cyanobacterial symbiotic combinations is still unclear. In addition, the association between non-cyanobacterial bacteria and lichens has attracted attention in recent years. The types, diversity, and functions of lichen-associated bacteria have been studied using both culture-based and culture-independent methods. This review summarizes the history of systematic research on lichens and lichen-associated bacteria and provides insights into the current status of research in this field.

Effects of ambient temperature on the redistribution efficiency of nutrients by desert cyanobacteria- Scytonema javanicum

Cultures of Scytonema javanicum obtained from artificial medium are used to control desertification, and through the effective redistribution of nutrients, related environmental problems can be alleviated. Wastewater is considered to be a potential alternative medium for S. javanicum. However, the effect of temperature on the nutrient redistribution ability of S. javanicum cultured in wastewater has rarely been considered. Therefore, this study explores the effect of temperature on S. javanicum in wastewater. The results showed that a sufficient temperature increase (from 25 °C to 30 °C) increased the photosynthetic activity of photosynthetic system II (PSII), accelerated the accumulation rate of S. javanicum biomass, and improved the removal efficiency of nutrients in wastewater. However, an increasing temperature caused a decrease in the final accumulated biomass. When the temperature was above 35 °C, the ratio of the variable to maximal fluorescence (Fv/Fm) of S. javanicum decreased, thus, causing damage to PSII. The average Fv/Fm at 35 °C and 40 °C decreased by 10.49% and 72.37%, respectively, compared to that at 25 °C. By analysing the chlorophyll fluorescence induction kinetics (OJIP) curve after 30 days, the P phase at 30 °C increased by 15.47% relative to that at 25 °C, whereas that at 35 °C and 40 °C decreased by 45.54% and 86.37%, respectively. In particular, at 40 °C, the O-J-I-P phase transformed into the O-J (J = I = P) phase, which caused irreversible damage to the PSII of S. javanicum. Comprehensive scores were determined using the entropy weight method and revealed that 30 °C was the optimal temperature for the wastewater culture of S. javanicum. This temperature improved the biomass accumulation rate and wastewater transfer efficiency. These results provide a scientific basis for improving the efficiency of the coupling technology of wastewater treatment and desert algal cultivation.

Symbiotic microalgal diversity within lichenicolous lichens and crustose hosts on Iberian Peninsula gypsum biocrusts

This study analyses the interactions among crustose and lichenicolous lichens growing on gypsum biocrusts. The selected community was composed of Acarospora nodulosa, Acarospora placodiiformis, Diploschistes diacapsis, Rhizocarpon malenconianum and Diplotomma rivas-martinezii. These species represent an optimal system for investigating the strategies used to share phycobionts because Acarospora spp. are parasites of D. diacapsis during their first growth stages, while in mature stages, they can develop independently. R. malenconianum is an obligate lichenicolous lichen on D. diacapsis, and D. rivas-martinezii occurs physically close to D. diacapsis. Microalgal diversity was studied by Sanger sequencing and 454-pyrosequencing of the nrITS region, and the microalgae were characterized ultrastructurally. Mycobionts were studied by performing phylogenetic analyses. Mineralogical and macro- and micro-element patterns were analysed to evaluate their influence on the microalgal pool available in the substrate. The intrathalline coexistence of various microalgal lineages was confirmed in all mycobionts. D. diacapsis was confirmed as an algal donor, and the associated lichenicolous lichens acquired their phycobionts in two ways: maintenance of the hosts' microalgae and algal switching. Fe and Sr were the most abundant microelements in the substrates but no significant relationship was found with the microalgal diversity. The range of associated phycobionts are influenced by thallus morphology.

Data variability or paradigm shift? Slow versus fast recovery of biological soil crusts-a review

Biological soil crusts, known also as biocrusts, provide valuable ecosystem services, especially in arid and semiarid regions. They may affect geomorphological (stability), hydrological (infiltration, evaporation), biochemical (carbon and nitrogen fixation) and ecological (germination and growth of vascular plants) processes, and their disturbance may have important ecological consequences. The common view, as reflected in hundreds of papers, regards biocrusts as having extremely slow recovery with characteristic time of up to hundreds and even thousands of years. Long recovery time implies that disturbance or climate change may have severe long-lasting consequences even once the conditions return to their initial state, triggering ample efforts to hasten biocrust recovery by inoculation. We critically analyze available estimates of the crust recovery time and present systematic measurements and theoretical considerations that attest to relatively rapid recovery of the crusts. We conclude that the likely recovery time of cyanobacterial crusts is 5-10 years, while that of lichen- and moss-dominated crusts is 10-20 years. Subsequently, costly and potentially negative effects to the ecosystem during inoculation should be weighed against the fast natural recovery of the biocrusts.

Warming reduces the cover, richness and evenness of lichen-dominated biocrusts but promotes moss growth: insights from an 8 yr experiment

Despite the important role that biocrust communities play in maintaining ecosystem structure and functioning in drylands world-wide, few studies have evaluated how climate change will affect them. Using data from an 8-yr-old manipulative field experiment located in central Spain, we evaluated how warming, rainfall exclusion and their combination affected the dynamics of biocrust communities in areas that initially had low (< 20%, LIBC plots) and high (> 50%, HIBC plots) biocrust cover. Warming reduced the richness (35 ± 6%), diversity (25 ± 8%) and cover (82 ± 5%) of biocrusts in HIBC plots. The presence and abundance of mosses increased with warming through time in these plots, although their growth rate was much lower than the rate of lichen death, resulting in a net loss of biocrust cover. On average, warming caused a decrease in the abundance (64 ± 7%) and presence (38 ± 24%) of species in the HIBC plots. Over time, lichens and mosses colonized the LIBC plots, but this process was hampered by warming in the case of lichens. The observed reductions in the cover and diversity of lichen-dominated biocrusts with warming will lessen the capacity of drylands such as that studied here to sequester atmospheric CO₂ and to provide other key ecosystem services associated to these communities.