Partição e dinâmica da interceptação pluviométrica em fragmento florestal com Eucalyptus spp.

Abstract

Rainfall interception by vegetation is a fundamental component of the forest water balance, regulating soil recharge, evapotranspiration, and surface runoff. Despite the widespread use of eucalyptus in reforestation programs, there remains a lack of quantitative assessments of rainfall redistribution beneath its canopy—particularly in transition zones between the Cerrado and Atlantic Forest biomes, such as the Alto Paranapanema Water Resources Management Unit (UGRHI-14). This study aimed to quantify and analyze rainfall interception fluxes in Eucalyptus spp. individuals within a forest fragment at the Lagoa do Sino campus (UFSCar) in Buri, São Paulo State, emphasizing the influence of meteorological variables and tree characteristics on rainfall redistribution. From December 2024 to June 2025, rainfall events were monitored using 18 rain gauges beneath three trees to measure throughfall, hoses attached to five trees to collect stemflow, and three external gauges to record gross precipitation. Local meteorological data—temperature, relative humidity, wind speed, solar radiation, and dew point—supported statistical analyses including Pearson’s and Spearman’s correlations and Principal Component Analysis (PCA). Throughfall accounted for 60–90% of gross rainfall, stemflow ranged from 1.5% to 11%, and canopy interception reached up to 23% during low-intensity events. Stemflow exhibited negative correlations with mean air temperature (r = −0.74) and dew point (r = −0.76), indicating greater trunk flow under cool and humid conditions. PCA identified two dominant gradients: an energy axis, comprising temperature, radiation, and solar input, which explained 59% of total variance; and a pluviometric axis, associated with total rainfall, throughfall, and rainfall variability, explaining 18.7%. These gradients delineate two distinct hydrological regimes: an energy-driven regime, characterized by enhanced evaporation and reduced canopy retention; and a rainfall-driven regime, marked by canopy saturation and increased stemflow. The findings of this preliminary investigation enhance the understanding of rainfall interception and redistribution processes in eucalyptus forests, providing valuable insights for water balance modeling, plantation management, and water resource conservation in ecologically transitional landscapes.