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.

Background and Aims The twig cross-sectional area and the surface area of leaves borne on it are expected to be isometrically correlated across species (Corner’s rules). However, how stable this relationship remains in time is not known. We studied the interspecific and intraspecific twig leaf area–cross-sectional area (la–cs) and other scaling relationships, including the leaf–shoot mass (lm–sm) scaling relationship, across a complete growing season. We also examined the influence of plant height, deciduousness and the inclusion of reproductive buds in the stability of the scaling relationships, and we discuss results from a functional perspective. Methods We collected weekly current-year twigs of 6 Patagonian woody species that differed in growth form and foliar habit. We also used Embothrium coccineum’s (Proteaceae) prominent inflorescences to assess whether or not reproductive buds alter the la–cs isometric relationship. Mixed effects models were fitted to obtain parameter estimates and to test whether interaction terms were nonsignificant (invariant) for the scaling relationships. Key Results The slope of the la–cs scaling relationship remained invariant across the growing season. Two species showed contrasting and disproportional (allometric) la–cs scaling relationships (slope ≠ 1). Scaling relationships significantly varied across growth form and foliar habit. The lm–sm scaling relationship differed between reproductive- and vegetative-origin twigs in E. coccineum, which was explained by a significantly lower leaf mass per area in the former. Conclusions Although phenology during the growing season appeared not to change leaf–shoot scaling relationships across species, we show that scaling relationships departed from the general trend of isometry as a result of within-species variation, growth form, foliar habit and the type of twig. The identification of these functional factors helps to understand variation in the general trend of Corner’s rules.

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Legítima dispersión de semillas