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Biocrusts are major contributors to dryland diversity, functioning, and services. However, little is known about how habitat degradation will impact multiple facets of biocrust diversity and measurable functional traits. We evaluated changes in taxonomic, functional, and phylogenetic diversity of biocrust-forming lichens along a habitat degradation gradient related to the presence of linear infrastructure (i.e., a road) and a profound agricultural driven transformation. To do so, we selected 50 remnants of a Mediterranean shrubland. We considered several surrogates of habitat quality and causal disturbance on the various diversity facets of biocrusts by using structural equation modeling, hypothesizing that habitat degradation primarily affects functional diversity, which in turn regulates changes in taxonomic and phylogenetic diversities, and also that taxonomic and phylogenetic diversities are coupled. Fragment connectivity, distance to linear infrastructure (i.e., a road) and, particularly, soil fertility (i.e., soil P concentration), had mostly negative effects on biocrust functional diversity, which in turn affected both taxonomic and phylogenetic diversities. However, we found no direct effects of habitat degradation variables on the taxonomic and phylogenetic diversities. We also found that increases in phylogenetic diversity had a positive effect on taxonomic diversity along the habitat degradation gradient. Our results indicate that functional diversity of biocrusts is strongly affected by habitat degradation, which may profoundly alter their contribution to ecosystem functioning and services. Furthermore, functional diversity regulates the response of biocrust taxonomic and phylogenetic diversity to habitat degradation. These findings indicate that habitat degradation alters and simplifies the diversity of functional traits of biocrust-forming lichens, leading to biodiversity loss, with important consequences for the conservation of global drylands biodiversity.

Understanding patterns of habitat natural recovery after human-made disturbances is critical for theconservation of ecosystems under high environmental stress, such as drylands. In particular, the unassisted estab-lishment of nonvascular plants such as biological soil crusts or biocrust communities (e.g., soil lichens, mossesand cyanobacteria) in newly formed habitats is not yet fully understood. However, the potential of biocrusts toimprove soil structure and function at the early stages of succession and promote ecosystem recovery is enor-mous. In this study, we evaluated the capacity of lichen biocrusts to spontaneously establish and develop on roadslopes in a Mediterranean shrubland. We also compared taxonomic and functional diversity of biocrusts betweenroad slopes and natural habitats in the surroundings. Biocrust richness and cover, species composition, and func-tional structure were measured in 17 road slopes (nine roadcuts and eight embankments) along a 13 km highwaystretch. Topography, soil properties and vascular plant communities of road slopes were also characterized. Weused Kruskal–Wallis tests and applied redundancy analysis (RDA) to test the effect of environmental scenario(road slopes vs. natural habitat) and other local factors on biocrust features. We found that biocrusts were com-mon in road slopes after∼20 years of construction with no human assistance needed. However, species richnessand cover were still lower than in natural remnants. Also, functional structure was quite similar between roadcuts(i.e., after soil excavation) and natural remnants, and topography and soil properties influenced species composi-tion while environmental scenario type and vascular plant cover did not. These findings further support the ideaof biocrusts as promising restoration tools in drylands and confirm the critical role of edaphic factors in biocrustestablishment and development in land-use change scenarios.

Livestock grazing is one of the most common practices in managed woodlands affecting the abundance and diversity of plant and soil communities. While grazing effects have been studied thoroughly in vascular plants, little is known about grazing consequences for soil lichens and mosses (“biocrusts”) in managed woodlands. However, these complex communities have critical contributions to soil functioning in drylands. We evaluated grazing effects on biocrust abundance and functional composition in Mediterranean cork-oak woodlands under long-term grazing and after 7 and 17 years of grazing exclusion. We found four main groups in the region regarding the functional trait ‘growth form’: fruticose and foliose lichens, and short and tall mosses. Each group presented different water absorption and retention capacity, and showed group-specific effects on soil water and temperature. Fruticose lichens were the most sensitive group to grazing, decreasing dramatically in cover with grazing (~7 times). Also, this group presented higher water retention capacity (~19 h), together with a consistent reducing effect on soil temperature along the grazing gradient (up to 0·9 °C). The shift in biocrust abundance and functional composition under grazing pressure has direct consequences in microclimate regulation, and is likely to influence other ecosystem processes such as CO2 fixation, soil surface protection and habitat provision. In particular, microclimate regulation may affect cork-oak regeneration processes, which is one of the main concerns in managed woodlands. Copyright © 2016 John Wiley & Sons, Ltd.

Functional traits are promising indicators of global changes and ecosystem processes. Trait responses to environmental conditions have been examined widely in vascular plants. In contrast, few studies have focused on soil lichens and mosses composing biocrusts. We aimed to evaluate the potential of biocrust tissue traits as indicators of changes in climate and soil properties. Isotope ratios and nutrient content in biocrust tissue were analyzed in 13 Mediterranean shrublands along an aridity gradient. Differences in tissue traits between biocrust groups (lichens and mosses), and relationships between tissue traits and climatic and soil variables were examined. Lichens and mosses differed in δ13C, δ15N and N content, indicating distinct physical and physiological attributes. Tissue traits correlated strongly with numerous climatic variables, likely due to a modulator effect on biocrust water relations and metabolism. We found contrasting responses of lichen and moss traits to climate, although they responded similarly to soil properties. Overall, the most responsive trait was δ15N, suggesting this trait is the best to reflect integrated processes occurring in the atmosphere and soil. Biocrust tissue traits arise as cost-effective, integrative ecological indicators of global change drivers in Mediterranean ecosystems, with potential applications in response-effect trait frameworks.

Biological soil crusts (or biocrusts) are widespread, diverse and important components of drylands sometimes threatened by global change drivers. However, their response to fragmentation processes is poorly known. The aim of this study was to assess the effects of changing landscape structure, given by land use change and the presence of linear infrastructure (e.g., roads), on the cover and diversity of lichen-biocrusts. We also evaluated the influence of several subrogates of fragment quality, such as soil properties, vascular plant community structure and topography. Biocrust cover and diversity were measured in 50 remnants of a Mediterranean shrubland. The fragments varied in size, connectivity and distance to a road, but also in plant and soil attributes, topography and fragment history. We applied general linear and mixed models to assess the effects of environmental variables on biocrust communities. Biocrust cover, richness and species composition were mostly unresponsive to changes in landscape structure, while connectivity and distance to the road decreased species diversity. Soil properties better explained the variation in biocrust cover and diversity. Changes in plant community and biocrust community composition were coupled. We also identified several biocrust species with strong capacity to reflect landscape structure. Our findings suggest that landscape structure needs to be evaluated jointly with other environmental factors to fully understand the consequences of fragmentation processes on biocrust communities and the subsequent implications for their functional role in drylands.

Grazing represents one of the most common disturbances in drylands worldwide, affecting both ecosystem structure and functioning. Despite the efforts to understand the nature and magnitude of grazing effects on ecosystem components and processes, contrasting results continue to arise. This is particularly remarkable for the biological soil crust (BSC) communities (i.e., cyanobacteria, lichens, and bryophytes), which play an important role in soil dynamics. Here we evaluated simultaneously the effect of grazing impact on BSC communities (resistance) and recovery after livestock exclusion (resilience) in a semiarid grassland of Central Mexico. In particular, we examined BSC species distribution, species richness, taxonomical group cover (i.e., cyanobacteria, lichen, bryophyte), and composition along a disturbance gradient with different grazing regimes (low, medium, high impact) and along a recovery gradient with differently aged livestock exclosures (short-, medium-, long-term exclusion). Differences in grazing impact and time of recovery from grazing both resulted in slight changes in species richness; however, there were pronounced shifts in species composition and group cover. We found we could distinguish four highly diverse and dynamic BSC species groups: (1) species with high resistance and resilience to grazing, (2) species with high resistance but low resilience, (3) species with low resistance but high resilience, and (4) species with low resistance and resilience. While disturbance resulted in a novel diversity configuration, which may profoundly affect ecosystem functioning, we observed that 10 years of disturbance removal did not lead to the ecosystem structure found after 27 years of recovery. These findings are an important contribution to our understanding of BCS dynamics from a species and community perspective placed in a land use change context.

Ajuts: This manuscript resulted from the 1st "Committee on Air Pollution Effects Research on Mediterranean Ecosystems" (CAPERmed) Conference celebrated in Lisbon, 2014 (http://capermed.weebly.com/). All attendants to this conference are, therefore, greatly acknowledged. Fundação para a Ciência e Tecnologia (FCT) is acknowledged through the Post Doc grant SFRH/BPD/85419/2012 to Teresa Dias and the Investigador grant to Silvana Munzi. ADM, EP and PS thank the LIFE10 ENV/FR/208 project MOTTLES. EP thanks also the Fondazione Cassa di Risparmio di Firenze (2013/7956). ROH is supported by a Juan de la Cierva Fellowship (IJCI-2014-21252) of the Spanish Ministry of Economy and Competitiveness. The authors declare no conflicts of interest. Mediterranean Basin ecosystems, their unique biodiversity, and the key services they provide are currently at risk due to air pollution and climate change, yet only a limited number of isolated and geographically-restricted studies have addressed this topic, often with contrasting results. Particularities of air pollution in this region include high O3 levels due to high air temperatures and solar radiation, the stability of air masses, and dominance of dry over wet nitrogen deposition. Moreover, the unique abiotic and biotic factors (e.g., climate, vegetation type, relevance of Saharan dust inputs) modulating the response of Mediterranean ecosystems at various spatiotemporal scales make it difficult to understand, and thus predict, the consequences of human activities that cause air pollution in the Mediterranean Basin. Therefore, there is an urgent need to implement coordinated research and experimental platforms along with wider environmental monitoring networks in the region. In particular, a robust deposition monitoring network in conjunction with modelling estimates is crucial, possibly including a set of common biomonitors (ideally cryptogams, an important component of the Mediterranean vegetation), to help refine pollutant deposition maps. Additionally, increased attention must be paid to functional diversity measures in future air pollution and climate change studies to establish the necessary link between biodiversity and the provision of ecosystem services in Mediterranean ecosystems. Through a coordinated effort, the Mediterranean scientific community can fill the above-mentioned gaps and reach a greater understanding of the mechanisms underlying the combined effects of air pollution and climate change in the Mediterranean Basin.

Understanding functional diversity is critical to manage and preserve biodi- versity and ecosystem functioning in the face of global change. However, the efforts to characterize this functional component have been mostly directed to vascular vegetation. We sampled lichen-dominated biological soil crusts (BSCs) in semiarid grasslands along an environmental gradient in the Iberian Peninsula. We characterized five effect functional traits for 31 lichens species, and evaluated the influence of large scale (i.e. precipitation) and small scale factors (i.e. substrate type, shrub presence, Stipa tenacissima presence) on dominant trait values; i.e. community weighted means, and functional divergence; i.e. Rao quadratic entropy in 580 sampling quadrats. Across the gradient, we found multiple trait shifts and a general increase of functional divergence with increasing precipitation. We also observed that substrate type and small scale biotic factors determined shifts in all traits studied, while these factors affected less to functional divergence. Comparing functional diversity with taxonomic diversity, we found contrasting responses to both large and small scale factors. These findings suggest that BSC community trait composition is influenced by multi-scale abiotic and biotic factors with environmental filtering dominating at large spatial scales and limiting similarity at specific small scales. Also, our results emphasize the potential differences between taxonomic and functional diversity in response to environmental factors. We concluded that functional diversity of BSCs not only provides novel and critical knowledge of BSC community structure, but also it should be considered

Biocrusts are key drivers of the structure and functioning of drylands and are very sensitive to disturbance, including atmospheric nitrogen (N) deposition. We studied the impacts of simulated N deposition on biocrust community composition and soil photosynthetic and photoprotective pigment content after five years of N application in a European semiarid Mediterranean shrubland. The experiment consisted in six experimental blocks with four plots, each receiving 0, 10, 20, or 50 kg NH4NO3-N ha-1 year-1 + 6-7 kg N ha-1 year-1 background. After 5 years of N application, total lichen cover decreased up to 50% compared to control conditions and these changes were only clearly evident when evaluated from a temporal perspective (i.e. as the percentage of change from the first survey in 2008 to the last survey in 2012). In contrast, moss cover did not change in response to N, suggesting that biocrust community alterations operate via species- and functional group-specific effects. Interestingly, between-year variations in biocrust cover tracked variations in autumnal precipitation, showing that these communities are more dynamic than previously thought. Biocrust species alterations in response to N were, however, often secondary when compared to the role of ecologically relevant drivers such as soil pH and shrub cover, which greatly determined the composition and inter-annual dynamics of the biocrust community. Similarly, cyanobacterial abundance and soil pigment concentration were greatly determined by biotic and abiotic interactions, soil pH for pigments, and organic matter content and shrub cover for cyanobacteria. Biocrusts, and particularly the lichen component, are highly sensitive to N deposition and their responses to pollutant N can be best understood when evaluated from a temporal and multivariate perspective, including impacts mediated by interactions with biotic and abiotic drivers.

Concostrina-Zubiri, L., Martinez, I., Huber-Sannwald, E., Escudero, A. 2013. Biological Soil Crust effects and responses in arid ecosystems: recent advances at the species level. Ecosistemas 22(3):95-000. Doi.: 10.7818/ECOS.2013.22-3.13. Biological soil crusts (BSCs) constitute a complex component of the ecosystem formed by different organisms (lichens, mosses, liverworts, cyanobacteria, fungi, algae) associated with soil surface. These communities are present in a wide variety of ecosystems; however, their abundance is generally higher in arid environments with sparse vegetation cover. In these ecosystems, BSCs greatly contribute to biodiversity and ecosystem functioning. Due to technical difficulties in species identification, most studies on BSCs have been carried out at community and morphotype levels. These studies have emphasized the potential role of BSCs in defining ecosystem structure and functioning by: interacting with topsoil layers and other soil organisms, participating in carbon and nitrogen fixation, and also in hydrological and nutrient cycling. Notwithstanding, recent advances in our knowledge about BSCs show substantial and interesting differences in the ecology and functional roles of BSC species, with marked implications in the management and conservation of these communities and their ecosystems. Particularly, it has been observed that BSC presence, abundance and frequency respond differently to diverse environmental factors (climatic variables, soil type, presence of vascular plants, and grazing disturbance - natural recovery) at the species level, and also do BSC effects on topsoil properties.

The family Gigaspermaceae consists of six, mostly Southern Hemisphere, genera. Three are monotypic: Costesia Ther. from Chile, Chamaebryum Ther. & Dixon from southern Africa, and Oedipodiella Dixon from South Africa and eastern Spain. The remaining three genera are each represented by just two species. Lorentziella Mull.Hal. is present in southern South America (Bolivia to Uruguay and Argentina), and from central Mexico to southeastern Texas (Fife, 1980). Of the two species of Neosharpiella H.Rob. & Delgad., N. turgida (Mitt.) H.Rob. & Delgad. was described from Ecuador and is also known from a few localities in western Bolivia and Chile. The other, N. aztecorum H.Rob. & Delgad., was once considered restricted to central Mexico (Fife, 1980). It has recently been reported from southern Africa (van Rooy & Perold, 2006), and also under its synonym Quathlamba debilicostata Magill (Magill, 1987). The genus Gigaspermum Lindb. is also represented by two species, G. repens (Hook.) Lindb. and G. mouretii Corb.; the latter is mainly restricted to the

Morphological and physiological characteristics of biological soil crusts (BSCs) enhance soil stability and fertility, and influence soil chemistry. However, the effect of BSCs on soil physico-chemical properties may vary depending on taxa (cyanobacteria, lichen, bryophytes) and species, and be susceptible to soil surface disturbance. We examined a wide variety of soil physico-chemical properties associated with five BSC components (cyanobacteria crust, one moss species, three lichen species) naturally occurring in the study area, and bare soil along a disturbance gradient in a semiarid grassland ecosystem in Central Mexico. We addressed the following questions: 1) Do different BSC components create distinct soil microsites characterized by a particular combination of physico-chemical properties? 2) Do distinct soil properties change beneath different BSC components? 3) Does grazing disturbance modify or override species-specific BSC effects? We found that BSC components and bare soil generated distinct soil microsites, however, this effect diminished with increasing grazing pressure. Also, most of the soil variables examined differed between BSC components and bare soil along the gradient. While soil properties associated with cyanobacteria were relatively similar compared to bare soil along the gradient, Diploschistes diacapsis and Lecidella sp. showed decreases in pH and marked differences in mineral nutrient concentration (i.e. variations in Na, Fe and Zn concentration respect to other BSC components and bare soil). Grazing intensity and frequency changed species-specific effects of D. diacapsis, specially modifying its effect on soil texture, diminishing its effect on pH, K and Na concentration, and increasing its effect on Ca and Zn concentration. We conclude that BSC components contribute to natural small-scale soil heterogeneity, and that soil disturbance substantially modifies the nature and magnitude of this effect with potentially important implications on ecosystem processes. Because of the potential influence of other factors (i.e. climate, vascular plants, microbial activity) on BSCs' relation to soil properties, this assertion should be tested including these factors and in multiple ecosystems.

Questions Environmental factors have been identified as strong modulators of plant community distribution and diversity, especially in arid and semi-arid ecosystems. Despite recent advances in the ecology of biological soil crusts (BSC) from a community perspective, much remains unknown at the species level. Do environmental factors at different scales influence species richness, diversity and composition of BSC communities? At the species level, what are the main predictors for species occurrence and frequency? Location A geographic gradient from southeast to central Spain. Methods In a geographic gradient, we characterized BSC communities based on species richness and diversity, species composition and species frequency. Using generalized linear mixed models (GLMMs) and multivariate analyses we evaluated the effect of precipitation, type of soil substrate, presence of shrubs and presence of Stipa tenacissima on community attributes. Results Precipitation positively influenced species richness and diversity, but had little effect on BSC occurrence at the species level. Type of substrate was a strong predictor for species composition, occurrence and frequency, gypsiferous soils being those with higher species richness and diversity. At the local scale, S. tenacissima had more effect on species occurrence and frequency, while shrub presence was a poor predictor of community attributes. Conclusions Environmental factors influence BSC diversity predominantly at a large scale, while local-scale factors influence both community diversity and species distribution.

La costra biológica del suelo (CBS) (cianobacterias, líquenes y briófitos) es un elemento clave en los ecosistemas de zonas áridas. La costra biológica del suelo mejora la estabilidad y la fertilidad del suelo, e influye en los procesos hidrológicos. El uso de suelo inadecuado, como pastoreo de ganado intenso puede alterar severamente la composición, cobertura y función de la CBS con una retroalimentación potencial negativa en los procesos del ecosistema. Por otra parte, es limitado el conocimiento sobre (Se conoce poco en general sobre) el grado hasta el cual pueden ser afectadas las comunidades de CBS debido a pastoreo de larga duración y su capacidad de recuperación tras la eliminación del pastoreo. Considerando el importante papel que la CBS tiene en los ecosistemas áridos y la degradación severa asociada con el pastoreo, el objetivo de esta investigación es examinar las comunidades de CBS bajo diferentes regimenes de pastoreo (gradiente de perturbación) y su recuperación potencial (gradiente de recuperación) con la eliminación del ganado en corto, mediano y largo plazo en los ecosistemas de pastizal del centro de México. En este contexto, enunciamos dos preguntas centrales. 1) ¿Cómo varía la riqueza de especies, la composición de la comunidad, la densidad de especies y la cobertura de la CBS a lo largo de i) un gradiente de perturbación con diferentes regimenes de pastoreo (moderado continuo (MCG, por sus siglas en inglés), intenso estacional (HSG) e intenso continuo (HCG)) y ii) un gradiente de recuperación del pastoreo con exclusiones de ganado de distinta antigüedad (exclusiones de corto plazo con 6 años de antigüedad (SGE, por sus siglas en inglés), de mediano plazo (MGE) con 11 años, y de largo plazo (LGE) con 27 años), considerando un ciclo intra-anual de estación seca y lluviosa? 2) ¿Distintas especies o taxones de CBS responden o afectan las características del suelo en pastizales afectados por pastoreo moderado continuo (MCG), intenso estacional (HSG) o intenso continuo (HCG) respecto a un pastizal con exclusión de ganado de largo plazo?

Despite their extent and socio-ecological importance, a comprehensive biogeographical synthesis of drylands is lacking. Here we synthesize the biogeography of key organisms (vascular and nonvascular vegetation and soil microorganisms), attributes (functional traits, spatial patterns, plant–plant and plant–soil interactions) and processes (productivity and land cover) across global drylands. These areas have a long evolutionary history, are centers of diversification for many plant lineages and include important plant diversity hotspots. This diversity captures a strikingly high portion of the variation in leaf functional diversity observed globally. Part of this functional diversity is associated with the large variation in response and effect traits in the shrubs encroaching dryland grasslands. Aridity and its interplay with the traits of interacting plant species largely shape biogeographical patterns in plant–plant and plant–soil interactions, and in plant spatial patterns. Aridity also drives the composition of biocrust communities and vegetation productivity, which shows large geographical variation. We finish our review by discussing major research gaps, which include: studying regular vegetation spatial patterns; establishing large-scale plant and biocrust field surveys assessing individual-level trait measurements; knowing whether the impacts of plant–plant and plant–soil interactions on biodiversity are predictable; and assessing how elevated CO2 modulates future aridity conditions and plant productivity., This review was done thanks to the support of the European Research Council (ERC grant agreement 647038 (BIODESERT)) and Generalitat Valenciana (CIDEGENT/2018/041). MB was supported by a Juan de la Cierva Fellowship from the Spanish Ministry of Science and Innovation (FJCI-2018-036520-I). LC-Z was supported by the Marie Sklodowska-Curie Actions (grant agreement 795380 (INDECRUST)) under the European Community’s H2020-EU.1.3.2 Programme. YLB-P was supported by a Marie Sklodowska-Curie Actions Individual Fellowship (MSCA-IF) within the European Program Horizon 2020 (grant agreement 656035 (DRYFUN)). SS was supported by the Ramón y Cajal program from the Ministry of Science and Innovation (RYC-2016-20604). MD-B was supported by the Ramón y Cajal program from the Spanish Ministry of Science and Innovation (RYC2018-025483-I), and by the British Ecological Society grant agreement no. LRB17\1019 (MUSGONET). RO-H was supported by the Ramón y Cajal program from the Spanish Ministry of Science and Innovation (RYC-2017 22032).

(1) Biocrusts are key drivers of ecosystem functioning in drylands, yet our understanding of how climate change will affect the chemistry of biocrust‐forming species and their impacts on carbon (C) and nitrogen (N) cycling is still very limited. (2) Using a manipulative experiment conducted with common biocrust‐forming lichens with distinct morphology and chemistry (Buellia zoharyi, Diploschistes diacapsis, Psora decipiens and Squamarina lentigera), we evaluated changes in lichen total and isotopic C and N and several soil C and N variables after 50 months of simulated warming and rainfall reduction. (3) Climate change treatments reduced δs13C and C:N ratio in B. zoharyi, and increased δ15N in S. lentigera. Lichens had species‐specific effects on soil dissolved organic N (DON), NH4+, β‐glucosidase and acid phosphatase activity regardless of climate change treatments, while these treatments changed how lichens affected several soil properties regardless of biocrust species. Changes in thallus δ13C, N and C:N drove species‐specific effects on DON, NH4+, β‐glucosidase and acid phosphatase activity. (4) Our findings indicate that warmer and drier conditions will alter the chemistry of biocrust‐forming lichens, affecting soil nutrient cycling, and emphasize their key role as modulators of climate change impacts in dryland soils. This research was funded by the European Research Council (ERC Grant Agreements 242658 [BIOCOM] and 647038 [BIODESERT] awarded to F.T.M), and by the Marie Skłodowska-Curie Actions (MSCA Grant Agreement 795380 [INDECRUST] awarded to L.C-Z.). E.V. was supported by the 2017 program for attracting and retaining talent of Comunidad de Madrid (no. 2017‐T2/ AMB‐5406). F.T.M. also acknowledges support from Generalitat Valenciana (CIDEGENT/2018/041).

Understanding patterns of habitat natural recovery after human-made disturbances is critical for the conservation of ecosystems under high environmental stress, such as drylands. In particular, the unassisted establishment of nonvascular plants such as biological soil crusts or biocrust communities (e.g., soil lichens, mosses and cyanobacteria) in newly formed habitats is not yet fully understood. However, the potential of biocrusts to improve soil structure and function at the early stages of succession and promote ecosystem recovery is enormous. In this study, we evaluated the capacity of lichen biocrusts to spontaneously establish and develop on road slopes in a Mediterranean shrubland. We also compared taxonomic and functional diversity of biocrusts between road slopes and natural habitats in the surroundings. Biocrust richness and cover, species composition, and functional structure were measured in 17 road slopes (nine roadcuts and eight embankments) along a 13 km highway stretch. Topography, soil properties and vascular plant communities of road slopes were also characterized. We used Kruskal–Wallis tests and applied redundancy analysis (RDA) to test the effect of environmental scenario (road slopes vs. natural habitat) and other local factors on biocrust features. We found that biocrusts were common in road slopes after ∼20 years of construction with no human assistance needed. However, species richness and cover were still lower than in natural remnants. Also, functional structure was quite similar between roadcuts (i.e., after soil excavation) and natural remnants, and topography and soil properties influenced species composition while environmental scenario type and vascular plant cover did not. These findings further support the idea of biocrusts as promising restoration tools in drylands and confirm the critical role of edaphic factors in biocrust establishment and development in land-use change scenarios.

Background and aims Biocrusts are major contributors to dryland nutrient cycling by regulating C, N and P inputs and fluxes. However, our understanding about how the decomposition of biocrust constituents contributes to soil nutrient cycling in drylands is virtually unknown. Methods We conducted a microcosm experiment to: i) evaluate the litter decomposition dynamics of two common biocrust-forming species with contrasting tissue chemistry and growth form (the lichen Cladonia foliacea and the moss Syntrichia caninervis), and ii) their effects on several soil variables related to soil functioning. Results Cladonia litter decomposed gradually with time (92% total mass loss after 342 days), while Syntrichia litter decomposed much faster (92% total mass loss after 62 days, with no further losses until the end of the experiment at 342 days). We observed species-specific effects of their litter on dissolved organic N (DON) and NH4+ depending on collection time, which changed the effects of litter decomposition on DON and pH regardless of the biocrust species considered. Overall, biocrust litter had a positive effect on SOC, DON, NH+4 and acid phosphatase activity. Conclusions Our experimental results show that decomposition of biocrust tissues plays an important role in soil nutrient cycling, indicating that this process impacts the fertility and functioning of dryland soils. This research was funded by the Marie Skłodowska-Curie Actions (MSCA Grant Agreement 795380 [INDECRUST] awarded to LCZ). FTM acknowledges support from the European Research Council (ERC Grant Agreement 647038 [BIODESERT]) and Generalitat Valenciana (CIDEGENT/2018/041). EV was supported by the 2017 program for attracting and retaining talent of Comunidad de Madrid (2017-T2/ AMB-5406).

Biocrusts are key drivers of ecosystem functioning in drylands, yet our understanding of how climate change will affect the chemistry of biocrust-forming species and their impacts on carbon (C) and nitrogen (N) cycling is still very limited.Using a manipulative experiment conducted with common biocrust-forming lichens with distinct morphology and chemistry (Buellia zoharyi, Diploschistes diacapsis, Psora decipiens and Squamarina lentigera), we evaluated changes in lichen total and isotopic C and N and several soil C and N variables after 50 months of simulated warming and rainfall reduction.Climate change treatments reduced δ13C and C:N ratio in B. zoharyi, and increased δ15N in S. lentigera. Lichens had species-specific effects on soil dissolved organic N (DON), , β-glucosidase and acid phosphatase activity regardless of climate change treatments, while these treatments changed how lichens affected several soil properties regardless of biocrust species. Changes in thallus δ13C, N and C:N drove species-specific effects on DON, , β-glucosidase and acid phosphatase activity.Our findings indicate that warmer and drier conditions will alter the chemistry of biocrust-forming lichens, affecting soil nutrient cycling, and emphasize their key role as modulators of climate change impacts in dryland soils.