Partitioning of the total evapotranspiration in a Japanese cypress plantation during the growing season

We investigated the contribution of three evapotranspiration (ET) components including canopy interception (E_i), tree transpiration (E_t) and forest floor evaporation (E_f) and identified the sources depth of evaporated water in a Japanese cypress stand. Monitoring primarily focused on the growing season of July-October 2011. In a 12×13 m plot with 28 trees with a DBH of 19.1±3.9cm, E_i was calculated as the difference between precipitation on an open field and precipitation under a canopy as the sum of throughfall and stemflow, and E_t was measured using the Granier method. E_f was measured by weighing lysimeters. Total ET during the monitoring period was 446.3mm, accounting for 47.5% of the total precipitation of 938.8mm. E_i was the dominant evaporation flux and accounted for 53.6% of ET or 25.5% of rainfall, followed by E_t with 33.7% of ET or 16.0% of rainfall. The average E_t was 1.5±0.6mmd^-1. It was well correlated with soil moisture at a depth of 5-15cm, which reflected the forest properties, i.e. tree roots were exposed on the forest floor. E_f accounted for 12.7% of ET or 6.0% of rainfall with a daily mean of 0.55±0.26mmd^-1, and was best correlated with soil moisture in the upper 5cm of soil. These results can improve the understanding of water budget in forested watershed and also be used to build and validate hydrologic models for water resource managements.