Stemflow and throughfall determination in a resprouted Mediterranean holm-oak forest

Stemflow, throughfall and precipitation data were collected for 30 consecutive months in a helm-oak forest dominated by Quercus ilex, Arbutus unedo and Phyllirea media. These flux data were obtained from 50 randomly distributed no-roving throughfall collectors and 20 stemflow measuring devices (ten on Q. ilex and five on each of the other species). The stemflow was highly influenced by tree size and amount of rainfall, showing a significant correlation for each tree. Throughfall results showed a high spatial variability for each storm, with a significant independence of collectors. At forest scale, stemflow and throughfall represented 12.1 and 75 % of precipitation, respectively, and interception was estimated as 12.9 % of precipitation. Partitioning of rainfall between stemflow and throughfall created a high spatial heterogeneity of water distribution under the canopy. Stemflow increased more than 30 times the mean amount of water received per unit soil area around tree trunks. Finally, the effect of a change in the amount of precipitation according to a regional scenario was analyzed. It was shown that the increase in high rainfall events rather than small events increased the stemflow percentage. (C) Inra/Elsevier, Paris.