Increased water use in dry season in eight dipterocarp species in a common plantation in the northern boundary of Asian tropics

Abstract

The seasonal water use and stand-level transpiration of the important tropical timber tree family, Dipterocarpaceae, have not been well investigated. Here, we characterized the seasonal water use and stand-level transpiration of eight, evergreen, dipterocarps in tropical Southwest China in the 2013 wet and dry seasons: six species grown in monoculture and two species in mixture. We estimated stand-level transpiration using a power model, combining data from 22 trees of all species measured in the two seasons. Despite significant decreases in soil volumetric water content within 1-m depth, predawn leaf water potentials (> −0.5 MPa) of all trees indicated access of roots to water. Daily sap flux density (SFDd) of all species closely responded to vapour pressure deficit (VPD). Dry season VPD increased by 29%, compared to in wet season, resulting 27–52% increased SFDd in six of the eight species. Whole tree daily water use was scaled with diameter at 1.3 m height for the 22 trees (r2 = 0.91 and 0.93 in the wet and dry seasons, respectively). Daily mean stand-level transpiration ranged from 0.63 to 2.23 mm d−1 (mean = 1.05) and from 1.18 to 2.29 mm d−1 (mean = 1.63) in the wet and dry seasons, respectively. Our results reveal conservative water use of dipterocarps and increased transpiration in dry season when a stable soil water source is available. In comparison with introduced fast-growing timber species, such as Eucalyptus and Acacia mangium, dipterocarp trees and forests consume much less water, making them more suitable as plantation timber crops for the region. Copyright © 2015 John Wiley & Sons, Ltd. Copyright © 2015 John Wiley & Sons, Ltd.