Relaciones hídricas en dos clones de Eucalyptus en sistema silvopastoriles

This study analyzes the water behavior of two forest species of interest in a silvopastoral alley cropping system with tree rows oriented north–south and different spatial planting arrangements. Clones of Eucalyptus dunnii and E. grandis were evaluated, arranged in single rows and triple rows. In the triple row system, three crown exposure positions were considered: east external (EE), internal (I), and west external (EO), with the objective of characterizing physiological variations and their responses to the environmental conditions of the system.

The study was carried out at the Bernardo Rosengurtt Experimental Station (Cerro Largo, Uruguay) between February and August 2024. The physiological variables analyzed included predawn and xylem water potential, stomatal conductance, and the dendrometric parameters of height, diameter at breast height (DBH), and percentage of live crown. Measurements were taken in both winter and summer of 2024 to assess the influence of water availability on the ecophysiological performance of the clones.

E. grandis showed an average height of 4.84 meters and a DBH of 5.08 centimeters, which were 1.20 meters and 1.5 centimeters greater, respectively, than E. dunnii, particularly in trees located in the east and internal positions of the triple row. Meanwhile, E. dunnii exhibited a 10–15% higher percentage of live crown than E. grandis, due to its lower tendency for basal branch mortality. In terms of water potential, both species showed similar values, although the EE position had lower water potential due to greater exposure to solar radiation and prevailing winds, which significantly increased transpiration demand.

Stomatal conductance was 228 mmol m² s⁻¹ in E. grandis, especially during winter, reflecting a greater capacity for gas exchange under favorable moisture conditions. E. dunnii showed a more conservative water-use strategy with a conductance of 161.23 mmol m² s⁻¹, which could be advantageous under limited water availability. In addition, results indicated that the triple-row design showed better overall performance, maximizing growth and resource-use efficiency.

This study provides relevant information for the management of silvopastoral systems with Eucalyptus spp., offering tools to improve productivity and sustainability by understanding how growth and physiology of the forest component are influenced.