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Alternative Biome States theory (ABS) helps to explain the presence of open biomes (grasslands, shrublands) in environments sufficiently warm and humid for the development of forest biomes. In these environments it is possible to find areas dominated by open biomes that, according to this theory, respond mainly to fire and herbivory. The aims of this work are to identify whether there are different types of forest biome-open biome ecotones based on woody composition, describe them and explore their relationship with livestock management and environmental variables, using a protected area in Uruguay as a case study. We sampled woody vegetation and other environmental variables in transects (delimited in 200m) in 10 sites across four livestock management systems. We identified two types of forest biome-open biome ecotones, one dominated by shrubland and the other dominated by grassland. Our results agree with the ABS theory and suggest the mechanisms determining the woody composition and the structure of the ecotone vegetation are cattle and use of fire and/or rotary cutter. The changes in vegetation structure and woody richness were partly abrupt, which is consistent with what is proposed by the ABS theory. However, the composition also interacted with site factors such as rockiness and distance to the watercourse, suggesting that site-level environmental variables are acting synergistically with vegetation removal to determine vegetation composition. We found that these ecotones are sensitive to management and environmental variables; so, it is necessary to incorporate this landscape and site heterogeneity to articulate productive activity with nature conservation. [ABSTRACT FROM AUTHOR]

Leaf functional traits in a plant community are the result of the effect of environmental conditions and have a direct impact on ecosystem properties and functioning. We analyzed the variations of five leaf functional traits in plant communities from central Argentina under different climatic conditions and anthropogenic use determining changes in physiognomy. Study sites were located in Córdoba province (Argentina) within four phytogeographic units categorized according to their climatic condition based on an aridity index; they were named as 'climatic units' 1, 2, 3 and 4, following a gradient from lower to higher temperature and aridity. In each climatic unit we selected six sites located in two physiognomies corresponding to different degrees of anthropogenic use: 3 sites in woodlands (less use), and 3 sites in grasslands/shrublands (more intense use). We measured five leaf traits (specific leaf area [SLA], leaf dry matter content [LDMC], leaf toughness, leaf thickness and decomposability), and we calculated the community weighted mean for each trait for each site. The variations in functional leaf traits were mainly determine by climatic conditions. The physiognomic change, because of anthropogenic use, also affected these variations, but this effect was conditioned by climate. Under colder and wetter climatic conditions, the removal of tree species result in communities dominate mainly by grasses with conservative foliar trait values (e.g., lower SLA, higher leaf toughness and lower decomposability). However, in warmer and drier climatic conditions, the removal of tree species did not imply a change in the functional strategy of the community as it resulted in an increase dominance of grasses and dicotyledonous shrub species with relatively lower foliar toughness and high decomposability. Our results show the interactive effect of climate and anthropogenic use on the variations in leaf functional traits and the complexity to predict the effects of such variations on ecosystem processes. [ABSTRACT FROM AUTHOR]