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Logging, grazing, wood extraction, and anthropogenic fires are pervasive throughout the subtropical dry vegetation of South America leading to changes in woodlands structure and ultimately its degradation. The Chac ohaco biome encompasses the second‐largest forest in South America and has a long history of intensive use. We sought to characterize the structure and heterogeneity of its woodlands across biogeographic subunits and climatic gradients, and evaluate structure controls. We quantified canopy height, cover, vertical complexity, vegetation amount above 3 m and total vegetation amount over 58 woodlands within the Argentinean Chaco by means of terrestrial laser scanner. We assessed the relationship between three groups near the maximum, average and minimum values of each structural variable and precipitation, temperature and temperature of the coldest month using quantile regressions. We found large variability in structural attributes within each biogeographical subunit, showing woodland areas with similar structure across broad gradients of climate. This suggests a considerable impact of current and past land use in shaping woodland structures across the Chaco. Overall, structural variables were positively associated with precipitation and temperature, albeit more strongly to the former, except for canopy height, which showed a strong association with mean temperature of the coldest month. We hypothesize that land‐use impact on woodland structure decreases with increasing precipitation, as the lack of water may limit the recovery of vegetation structure. Our results contribute to a better understanding of variation in key structural variables of Chaco woodlands in relation to climate and land use. [ABSTRACT FROM AUTHOR]

Climate change and energy security promotes using renewable sources of energy such as biofuels. High woody biomass production achieved from short rotation intensive plantations is an appealing strategy that is growing in many parts of the world. However, broad expansion of bioenergy feedstock production may have significant environmental consequences. This study investigates the watershed-scale hydrological impacts of eucalyptus plantations for energy production in a humid subtropical watershed in Entre Rios province, Argentina. A Soil and Water Assessment Tool (SWAT) model was calibrated and validated for streamflow, leaf area index (LAI), and biomass production cycles. The model was used to simulate various eucalyptus plantation scenarios that followed physically-based rules for land use conversion (in various sizes and locations in the watershed) to study hydrological effects, biomass production and the green water footprint of energy production. SWAT simulations indicated that the most limiting factor for plant growth was shallow soils causing seasonal water stress. This resulted in a wide range of biomass productivity throughout the watershed. An optimization algorithm was developed to find the best location for eucalyptus development regarding highest productivity with least water impact. Eucalyptus plantations had higher evapotranspiration rates among terrestrial land cover classes; therefore, intensive land use conversion to eucalyptus caused a decline in streamflow, with February, January and March being the most affected months. October was the least-affected month hydrologically, since high rainfall rates overcame the canopy interception and higher ET rates of eucalyptus in this month. Results indicate that, on average, producing 1 kg of biomass in this region uses 0.8 m³ of water, and the green water footprint of producing 1 m³ fuel is approximately 2150 m³ water, or 57 m³ water per GJ of energy, which is lower than reported values for wood-based ethanol, sugar cane ethanol and soybean biodiesel. [ABSTRACT FROM AUTHOR]