Characterizing microenvironmental factors and the forest component in the production of natural grasslands in a silvopastoral system with Eucalyptus grandis

Integrating livestock with afforestation in Silvopastoral Systems (SPS) can enhance livestock production while mitigating climate and economic fluctuations. In SPS, tree canopies modify solar radiation and wind speed, affecting pasture evapotranspiration and water availability. This work aims to contribute to understanding tree-pasture-environment interactions and the light-use efficiency of natural grassland in SPS with fast-growing forest species. The study site is in Reboledo, Florida, Uruguay (34° 1′15.16″S, 55°39′13.75″W), consisting of natural pastures lined with triple rows of Eucalyptus grandis and 14–19 m alleys. Two experiments were conducted, one in the field and one in growth chamber. Plots were established in three different tree ages (2012 (10y), 2013 (9y), 2019 (3y)) and a control. Each tree age had three zones relative to tree lines (Row (R), Intermediate (I) and Middle Alley (MA)). Results showed that variations between zones were less pronounced in the 10y trees compared to the 3y trees. Accumulated PAR differences ranged from 32% in 10y trees to 38% in 3y trees, in tree LAI (28–76%) and Soil Water Content (WC) (31–51%). Accumulated PAR in MA zone (3y trees) did not differ from the control without trees. Soil WC in R is the lowest among all situations in 3y plot and the highest in the 10y. Photosynthetic Active Radiation Use Efficiency (PARUE) for natural grassland sod pieces under simulated shade averaged 0.40 g mol⁻¹. Younger trees generated a more heterogeneous system with more pronounced zones, where the middle alley resembles the control without trees in the studied variables.