Measurements of evapotranspiration processes in a Japanese cedar forest in Xitou, Taiwan

Abstract:

The forests in Taiwan situated in the mountain regions from 500 to 2,500 m asl are so-called the montane cloud forest ecosystem, frequently affected by fog. In such forests, wet canopy evaporation can account for a significant proportion of ecosystem evapotranspiration, which may reduce the relative importance of tree transpiration. Because tree transpiration is very closely related to soil water dynamics, a quantitative assessment of tree transpiration is essential to elucidate ecohydrological processes in such forests. At the same time, since the tree transpiration and the wet canopy evaporation are tightly interrelated, and the characteristics of wet canopy evaporation is still unknown, the quantitative evaluations of tree transpiration and wet canopy evaporation are both necessary. The Xitou long-term ecosystem research site (23°39’57” N, 120°47’44.5” E, 1267 m above mean sea level) in the Experimental Forest of National Taiwan University is located in the Nantou County, Central Taiwan, where the flux and meteorological measurements are conducted since 2009 on the tower with the height of 40 m in a plantation of Japanese cedar (Cryptomeria japonica). According to the simulation results by a terrestrial ecosystem dynamics model (S-TEDy), wet canopy evaporation may account for a large proportion of the evapotranspiration in this cloud forest in Taiwan, prompting interests in how the contributions of transpiration and evaporation are separated.

As the first step of this study, we will present the characteristics of evapotranspiration in a Japanese cedar forest in Xitou research site, by comparing the eddy covariance fluxes measured at the tower top and forest floor in this presentation.

This research was supported by MOST (grant #108-2313-B-002-009-).