Variability of annual rainfall partitioning for different sites and forest covers in Chile

Precipitation, throughfall, stemflow and interception losses were determined in Chile on 29 research plots grouped in nine research sites, covering a wide range of rainfall zones, forest types, species, ages and densities. All the data are presented and analyzed on a 12-month time base. Throughfall varied between 55 and 86% of precipitation (P) and although it was higher in coniferous stands than in broadleaved forests the differences were not statistically significant. Stemflow varied from 1 to 13% of P in coniferous stands and between 1 and 8% of P in broadleaved forests. Stemflow for individual trees was higher under high annual rainfall and in low dense forests, and decreased when annual precipitation reduced and forest density increased. In broadleaved stands interception losses (I) ranged from 204 to 1097 mm/year while in coniferous forests I showed a narrower range of variation from 199 to 579 mm/year. Because the final effect of the replacement of native forests by plantations upon water yield also depends on transpiration and other evaporation losses, it was not possible to conclude that this substitution will increase water availability. In a Monterey pine stand interception losses increased with the age of the forest because of the tendency for the branches of this conifer to become horizontal, thus increasing interception capacity and decreasing stemflow. In a native forest that had reached its climax state interception losses decreased during nine years of measurement associated with the continuous reduction of interception capacity of the dense bamboo understorey.