Our results highlight that nurse plants not only increase the number of species able to colonize a given site, but may also promote species coexistence by preventing the local extinction of rare species. Our findings illustrate the role that nurse plants play in conserving endangered species and link the relationship between facilitation and diversity with coexistence theory. As such, they provide further mechanistic understanding on how facilitation maintains plant diversity.

Our results showed that: (a) the degree of community specialization to aridity mediates the relative importance of plant–plant interactions in determining species abundances and (b) facilitation and competition were more strongly related to species abundance in communities dominated by generalists and specialists, respectively. We observed a shift from facilitation to competition as drivers of species abundances as aridity increases in global drylands. Our findings also pave the way to develop more robust predictions about the consequences of ongoing climate change on the assemblage of plant communities in drylands, the largest terrestrial biome.

Our results indicate that climate change will have negative direct and indirect (i.e. through changes in biocrust and microbial communities) impacts on the resistance of the N cycle in dryland soils. While biocrusts can play an important role slowing down the impacts of climate change on the N cycle due to their positive and continued effects on the resistance of multiple variables from the N cycle, such change will progressively alter N cycling in biocrust-dominated ecosystems, enhancing both N availability and inorganic N dominance.

Our modelling results show that a decrease in relative humidity, rather than an increase in temperature, may be the key factor for the survival of the lichen D. diacapsis under climate change and that effects of increased CO₂ levels might be offset by a reduction in non-rainfall water inputs in the future. Because of a global trend towards warmer and drier air and the widespread global distribution of D. diacapsis, this will affect lichen-dominated dryland biocrust communities and their role in regulating ecosystem functions worldwide.

Using a novel trait-based and multiscale approach, we show that competition and facilitation jointly determine the functional structure of Mediterranean shrublands along a large aridity gradient. Competition mostly impacted on dominant plant species whereas facilitation affected subordinate and rare species. Overall, shift from competition to facilitation appears to be trait-dependent along the aridity gradient.

We used 311 sites across a broad natural gradient in Patagonian rangelands to evaluate the relative importance of climate (temperature, precipitation) and vegetation structure (grass and shrub cover, species richness) as drivers of above-ground net primary productivity, precipitation-use efficiency and precipitation marginal response. We found that vegetation structure is as important as climate in shaping ecosystem functioning. Maintaining and enhancing vegetation cover and species richness, particularly of grasses, could reduce the adverse effects of climate change on ecosystem functioning.

We identified the particular set of conditions under which the environmental filtering hypothesis operates in drylands world-wide. Our findings also indicate that species with functionally contrasting strategies can still co-occur locally, even under prevailing environmental filtering. Interactions between sources of environmental stress should be therefore included in global trait-based studies, as this will help to further anticipate where the effects of environmental filtering will impact plant trait diversity under climate change.

Our results show that the most fertile islands in global drylands are found at lower elevation sites with greater soil pH values and sand content under semiarid climates, particularly at locations where the presence of tall woody species with a low-specific leaf area increased fungal abundance beneath plant canopies. Our study also has broad implications for the management and restoration of dryland ecosystems worldwide, where woody plants are commonly used as nurse plants to enhance the establishment and survival of beneficiary species. Finally, our results suggest that forecasted increases in aridity may enhance the formation of fertile islands in drylands worldwide.