Produtividade e uso de água de plantações de Eucalyptus uroplylla em gradiente climático no Brasil

Abstract

Eucalyptus plantations play a strategic role in supplying timber, pulp, and bioenergy, supporting one of the world's most productive forest sectors. In Brazil, E. urophylla is widely recognized for its high productivity and broad adaptation to diverse edaphoclimatic conditions. However, the mechanisms that enable this species to sustain high productivity under water-limited conditions, as well as the implications of this dependence for the long-term sustainability of forestry under increasing climate variability, remain poorly understood. To address these questions, this thesis was conducted in two complementary stages. First, the process-based ecophysiological model ECOSMOS was improved to provide a more realistic representation of the processes controlling growth and water use in E. urophylla plantations. The improved model was then applied to evaluate the effects of climate variability on productivity and water use across thirty-six forest rotations distributed along a 3,500-km environmental gradient in Brazil, using meteorological data from 1980 to 2022. The model successfully reproduced the coupling among energy, water, and carbon fluxes, demonstrating robust performance in simulating tree growth under contrasting edaphoclimatic conditions. The attainable mean annual increment (MAI) averaged 44 m³ ha⁻¹ yr⁻¹, ranging from 19 to 62 m³ ha⁻¹ yr⁻¹, with the highest productivity occurring under mean annual temperatures between 19 and 26 °C and annual precipitation between 1,250 and 1,750 mm. Trend analysis revealed increasing MAI in humid regions but declining MAI in regions with a dry-winter climate (Cw), accompanied by a long-term decrease in precipitation. Mean transpiration corresponded to approximately 82% of annual precipitation and, at some sites, exceeded annual rainfall, indicating that sustained productivity depends not only on current precipitation but also on water stored within the soil profile and, potentially, on groundwater access. These findings suggest that the observed decline in precipitation in Cw regions may reduce groundwater recharge and soil water availability, potentially compromising plantation resilience and intensifying competition for water resources. Overall, this thesis advances the understanding of the ecophysiological mechanisms regulating growth and water use in E. urophylla plantations and establishes ECOSMOS as a robust decision-support tool for estimating attainable productivity, assessing climate-related risks, and supporting climate suitability zoning, forest planning, and climate adaptation strategies for Brazilian forestry.