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

ABSTRACT

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 ± 3.9 cm, 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 446.3 mm, accounting for 47.5% of the total precipitation of 938.8 mm. 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 ± 0.6 mm d⁻¹. It was well correlated with soil moisture at a depth of 5–15 cm, 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 ± 0.26 mm d⁻¹, and was best correlated with soil moisture in the upper 5 cm 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. Copyright © 2013 John Wiley & Sons, Ltd.