Despite Similar Evapotranspiration, Eucalyptus Show Lower Soil Water Depletion Than Adjacent Native Forest

ABSTRACT

The hydrological effects of Eucalyptus plantations on landscapes remain controversial. Previous studies have identified these plantations as a major contributor to soil‐water depletion, reduced groundwater recharge and lower baseflow relative to native forests. In Brazil, the area under Eucalyptus cultivation has expanded substantially in recent decades, raising concerns about potential ecohydrological impacts. Direct comparisons of the hydrological behaviour of Eucalyptus plantations and Atlantic Forest remnants under similar climatic and topographic conditions, and on soils within the same taxonomic class, are needed to clarify these effects, because comparable water balance totals may conceal distinct hydrological pathways in the two forest types. This paper compares water balance components between a mature Eucalyptus plantation and an adjacent semi‐deciduous Atlantic Forest remnant over four hydrological years (2013–2017). Both study sites share the same soil type (Dystroferric Red Latosol), climate and physiographic conditions. We monitored throughfall (TF), stemflow (SF), soil moisture to 1.0 m depth and meteorological data, enabling calculation of water balance, focusing on evapotranspiration (ET), canopy interception (CI), percolation (Pp) and soil water storage (SWS). The observation period comprised 1172 days for Eucalyptus and 1295 days for Atlantic Forest, with gross precipitation (GP) totalling 3659.4 and 4665.7 mm, respectively. ET accounted for 86.21% of GP in Eucalyptus versus 79.44% in Atlantic Forest. TF represented 71.52% (Eucalyptus) and 77.01% (Atlantic Forest) of GP, while SF displayed the greatest relative difference: 3.49% for Eucalyptus compared to 1.57% for Atlantic Forest. Pp from the 1.0 m soil layer was 12.72% (Eucalyptus) and 14.73% (Atlantic Forest) of GP. The Atlantic Forest exhibited higher water input to the forest floor but also greater percolation, leading to a more pronounced cumulative soil water deficit (−942 mm) by the end of the study period compared to the Eucalyptus site (−551 mm). This is likely due to the higher organic matter and biological activity in the Atlantic Forest, which enhance infiltration, accelerating deep drainage. Despite similar evapotranspiration, the Eucalyptus plantation exhibited lower soil water depletion than the adjacent native forest, which has been more severely affected by droughts, with implications for water resources management and land‐use planning in tropical regions.