Land degradation is one of the main threats to dryland sustainability in the next decades, hence restoration of the degraded land from drylands is an urgent need to maintain ecosystem functionality and their ability to provide ecosystem services. To achieve this goal, restoration practices should pursue the recovery of the main ground components, arranged in an optimal spatial configuration, to mimic undisturbed natural conditions. Drylands function as complex ecohydrologically coupled systems in which interplant source areas, frequently covered by biocrusts, act as sources of runoff and nutrients to adjacent vegetation, which act as sinks for these resources. Thus, one way to increase dryland restoration success is through an optimal spatial configuration of biocrusts and plants that maximizes an efficient use of the limited resources within the system. In this study, we selected a degraded slope from a limestone quarry located in Almería province (SE Spain) and modeled how active restoration of the biocrust through soil inoculation with cyanobacteria and its combination with different spatial configurations of vegetation affected runoff redistribution and erosion. For that, we applied the spatially distributed Limburg Soil Erosion Model (LISEM) which was able to predict the erosion measured on the slope during the study period with low error (RMSE = 17.8%). Modeling results showed that the introduction of vegetation on the degraded slope reduced runoff between 2 and 24% and erosion between 4 and 17% for the scenario with plants compared to the one without restoration management. Of all the vegetation spatial configurations tested, the one that provided better results was the scenario in which plants were located in the areas of higher water accumulation (higher topographic wetness index). Moreover, we found that active biocrust restoration by cyanobacteria inoculation significantly reduced erosion by 70–90%, especially during the first stages of plant development, while maintaining water supply to vegetation. These findings highlight the potential of water redistribution and erosion simulation models to identify the most optimal spatial configuration of ground covers that maximizes water and nutrient supply to vegetation, while minimizes water, sediment, and nutrient losses by erosion, thus serving as an efficient tool to plan restoration actions in drylands.

The Mediterranean region is experiencing a stronger warming effect than other regions, which has generated a cascade of negative impacts on productivity, biodiversity, and stability of the ecosystem. To monitor ecosystem status and dynamics, aboveground biomass (AGB) is a good indicator, being a surrogate of many ecosystem functions and services and one of the main terrestrial carbon pools. Thus, accurate methodologies for AGB estimation are needed. This has been traditionally done by performing direct field measurements. However, field-based methods, such as biomass harvesting, are destructive, expensive, and time consuming and only provide punctual information, not being appropriate for large scale applications. Here, we propose a new non-destructive methodology for monitoring the spatiotemporal dynamics of AGB and green biomass (GB) of M. tenacissima L. plants by combining structural information obtained from terrestrial laser scanner (TLS) point clouds and spectral information. Our results demonstrate that the three volume measurement methods derived from the TLS point clouds tested (3D convex hull, voxel, and raster surface models) improved the results obtained by traditional field-based measurements. (Adjust-R2 = 0.86–0.84 and RMSE = 927.3–960.2 g for AGB in OLS regressions and Adjust-R2 = 0.93 and RMSE = 376.6–385.1 g for AGB in gradient boosting regression). Among the approaches, the voxel model at 5 cm of spatial resolution provided the best results; however, differences with the 3D convex hull and raster surface-based models were very small. We also found that by combining TLS AGB estimations with spectral information, green and dry biomass fraction can be accurately measured (Adjust-R2 = 0.65–0.56 and RMSE = 149.96–166.87 g in OLS regressions and Adjust-R2 = 0.96–0.97 and RMSE = 46.1–49.8 g in gradient boosting regression), which is critical in heterogeneous Mediterranean ecosystems in which AGB largely varies in response to climatic fluctuations. Thus, our results represent important progress for the measurement of M. tenacissima L. biomass and dynamics, providing a promising tool for calibration and validation of further studies aimed at developing new methodologies for AGB estimation at ecosystem regional scales.

<p>Biocrusts play a key role in maintaining drylands ecosystems at the global scale. These keystone communities face important human[ERC1]  threats (e.g. climate change) that can result in both biocrust coverage loss and community composition changes and are expected to negatively affect soil biodiversity, and the functioning and resilience of drylands ecosystems. In this adverse scenario, there is an urgent need to develop legal science-based frameworks that underpin their protection. The social-ecological approach, as a research framing oriented to produce scientific knowledge able to properly inform policy actions and management practices, can help us to advance in this direction. By reviewing literature in Spanish biocrusts from the social–ecological approach, here we found that the ecological scope</p><p>of biocrust has been widely studied in the last decades; however, the social dimension of their role remained unexplored. In addition, we identified knowledge gaps and new research areas that need to be addressed in order to (1) produce research that better informs policy and society about the role of these keystone communities, and (2) promote the best available evidence on the biocrusts role which can be used to support conservation actions. On this basis, we call for a transition from an “ecological research perspective” to a “social–ecological research perspective” into the biocrust area in order to promote evidence-based conservation practices that contribute to the preservation of these representative communities of drylands all over the world.</p>

<p>Nowadays, land use change and the impacts of climate change are accelerating land degradation processes in drylands. These regions occupy around 40% of the Earth land’s surface and their extension is likely to represent around 45% by 2050. Biocrusts (complex communities formed by bacteria, cyanobacteria, microalgae, fungi, lichens and mosses which live in the uppermost layer of soil and can cover up to 70% of the interplant areas) play a decisive role in soil stabilization and fertility in these regions, so that they have been proposed as restoration agents in degraded dryland sites, where water scarcity and the harsh environmental conditions can hinder traditional restoration based on the use of vegetation establishment. Within the different biocrust-forming organisms, the use of cyanobacteria as a biotechnological tool to combat soil degradation, is gaining increasing importance. Cyanobacteria are the pioneer colonizers of terrestrial ecosystems, they are able to resist extreme environmental conditions, i.e. high temperatures, prolonged UV radiation and nutrients scarcity. At the same time, they improve physical-chemical properties of the soil by fixing carbon and many species also the atmospheric nitrogen and by producing exopolysaccharides that strongly increase soil stability and eventually creating a more favorable environment for colonization by other organisms. Despite several laboratory studies demonstrate the effectiveness of inoculating soil with cyanobacteria and their effect in increasing soil carbon and nutrient content, few field studies are available and many of them show a limited success probably because of the harsh environmental conditions that hamper an optimal growth. In the present work, soils collected from different ecosystems  in SE Spain were inoculated with a consortium of four native cyanobacteria species: Nostoc comune, Trichocoleus desertorum, Tolypothrix distorta and Leptolyngbia sp., and  different techniques to reduce abiotic stresses were tested in outdoors conditions: 1) cyanobacteria + soil covered with a mesh made of Stipa tenacissima, 2) cyanobacteria+ Plantago-based stabilizer amendment, and 3) cyanobacteria + sewage sludge (incorporated as an organic amendment) . The application of plant-based ameliorating strategies resulted in a higher chlorophyll a content, which reflects an improvement of cyanobacterial growth compared to the inoculation lacking the application of ameliorating techniques. The soil albedo also decreased due to surface darkening, thus also indicating a higher cyanobacterial growth in these treatments. Wind tunnel experiments also demonstrated a lower susceptibility to wind erosion in the cyanobacteria-inoculated soils combined with application of the plant mesh or the Plantago amendment. These results highlight the importance of using plant-based amelioration techniques to reduce abiotic stresses, especially in the early stages of soil colonization after cyanobacteria inoculation. Regarding the use of sewage sludge, it was demonstrated that their application at low doses improved cyanobacteria growth, which was reflected in an increase in chlorophyll a content as well as in a significant increase of aggregate stability and reduced soil susceptibility to wind erosion. This study shows promising results to enhance cyanobacterial growth and prevent cyanobacteria inoculum loss under natural conditions. Ongoing experiments will evaluate the effectiveness of these strategies under field conditions.</p>

Sewage sludge (SS) is widely used as a soil conditioner in agricultural soil due to its high content of organic matter and nutrients. In addition, inoculants based on soil microorganisms, such as cyanobacteria, are being applied successfully in soil restoration to improve soil stability and fertility in agriculture. However, the combination of SS and cyanobacteria inoculation is an unexplored application that may be highly beneficial to soil. In this outdoor experiment, we studied the ability of cyanobacteria inoculum to grow on degraded soil amended with different concentrations of composted SS, and examined the effects of both SS concentration and cyanobacteria application on carbon gain and soil stability. We also explored the feasibility of using cyanobacteria for immobilizing salts in SS-amended soil. Our results showed that cyanobacteria growth increased in the soil amended with the lowest SS concentration tested (5 t ha−1, on soil 2 cm deep), as shown by its higher chlorophyll a content and associated deeper spectral absorption peak at 680 nm. At higher SS concentrations, inoculum growth decreased, which was attributed to competition of the inoculated cyanobacteria with the native SS bacterial community. However, SS significantly enhanced soil organic carbon gain and tightly-bound exopolysaccharide content. Cyanobacteria inoculation significantly improved soil stability and reduced soil’s wind erodibility. Moreover, it led to a decrease in the lixiviate electrical conductivity of salt-contaminated soils, indicating its potential for salt immobilization and soil bioremediation. Therefore, cyanobacteria inoculation, along with adequately dosed SS surface application, is an efficient strategy for improving carbon gain and surface stability in dryland agricultural soil.