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Earth harbours an extraordinary plant phenotypic diversity 1 that is at risk from ongoing global changes 2,3 . However, it remains unknown how increasing aridity and livestock grazing pressure-two major drivers of global change 4-6 -shape the trait covariation that underlies plant phenotypic diversity 1,7 . Here we assessed how covariation among 20 chemical and morphological traits responds to aridity and grazing pressure within global drylands. Our analysis involved 133,769 trait measurements spanning 1,347 observations of 301 perennial plant species surveyed across 326 plots from 6 continents. Crossing an aridity threshold of approximately 0.7 (close to the transition between semi-arid and arid zones) led to an unexpected 88% increase in trait diversity. This threshold appeared in the presence of grazers, and moved toward lower aridity levels with increasing grazing pressure. Moreover, 57% of observed trait diversity occurred only in the most arid and grazed drylands, highlighting the phenotypic uniqueness of these extreme environments. Our work indicates that drylands act as a global reservoir of plant phenotypic diversity and challenge the pervasive view that harsh environmental conditions reduce plant trait diversity 8-10 . They also highlight that many alternative strategies may enable plants to cope with increases in environmental stress induced by climate change and land-use intensification., (© 2024. The Author(s), under exclusive licence to Springer Nature Limited.)

Grazing represents the most extensive use of land worldwide. Yet its impacts on ecosystem services remain uncertain because pervasive interactions between grazing pressure, climate, soil properties, and biodiversity may occur but have never been addressed simultaneously. Using a standardized survey at 98 sites across six continents, we show that interactions between grazing pressure, climate, soil, and biodiversity are critical to explain the delivery of fundamental ecosystem services across drylands worldwide. Increasing grazing pressure reduced ecosystem service delivery in warmer and species-poor drylands, whereas positive effects of grazing were observed in colder and species-rich areas. Considering interactions between grazing and local abiotic and biotic factors is key for understanding the fate of dryland ecosystems under climate change and increasing human pressure.

Knowledge of the arbuscular mycorrhizal fungal assemblages in the Trachypogon savanna ecosystems is very important to a better understanding of the ecological processes mediated by this soil microbial group that affects multiple ecosystem functions. Considering the hypothesis that the biocrusts can be linked to vegetation through the arbuscular fungi mycelial network, the objectives proposed in this study were to determine (i) whether there are arbuscular mycorrhizal fungi (AMF) in the biocrusts (ii) whether arbuscular mycorrhizal fungal assemblages are linked to the Trachypogon patches, and (iii) whether the composition of the assemblages is related to soil properties affected by microbiological activity. The community structure of the AMF was investigated in three habitats: rhizospheric soil and roots of Trachypogon vestitus, biological soil crusts, and bare soil. The canonical correspondence analysis showed that two soil properties related to enzymatic activity (protease and β-glucosidase) significantly affected the community composition of the AMF. The biocrusts in the Venezuelan savanna are colonized by an AM fungal community linked to that of the bare soil and significantly different from that hosted by the roots of the surrounding T. vestitus, suggesting that assemblages of AMF in biocrusts might be related more closely to those of annual plant species appearing in favorable conditions., (Copyright © 2016 Elsevier B.V. All rights reserved.)