Transpiration, canopy conductance and the decoupling coefficient of a lowland mixed dipterocarp forest in Sarawak, Borneo: dry spell effects
Transpiration, canopy conductance and the decoupling coefficient of a lowland mixed dipterocarp forest in Sarawak, Borneo: dry spell effects
复制标题
DOI：
10.1016/j.jhydrol.2003.10.002
复制
发表时间：
2004-02-25
影响因子：
6.4
通讯作者：
Suzuki, M
中科院分区：
文献类型：
--
作者：
Kumagai, T;Saitoh, TM;Suzuki, M
热带雨林在年第一性生产力和水分循环方面是最重要的生物群落之一，然而，东南亚森林的物质交换特性在其重要功能方面的研究较少。我们研究了控制物质交换的关键因素，如树冠(G)和空气动力导度(G)。以及婆罗洲沙捞越一个完整的低地混交林中的去耦合系数(N)。我们利用80米高的吊车在冠层上方安装了涡旋协方差系统来测量冠层蒸腾速率，并进行了同步气象测量。在该地区，太阳辐射和气温的季节变化很小，全年降雨量分布均匀，年内出现一些不可预测的干旱时段。根据干旱程度，我们定义了A、B、C三个特定时期，分别为中干、重干和湿润时期，以分析对E的环境控制。丰水期C的日均E、g和D均高于枯水期A和B，且各g的日变化在丰水期C显著高于枯水期A和B，两者的日变化基本相同。潮湿时期C的g值及其对环境变量的敏感度均高于干燥时期A和B。n的峰值在潮湿时期C高于干燥时期A和B，这是因为C时期的Gc值较高。但与干燥时期A和B相比，潮湿时期C的Gc值较高并不会导致E较高。(C)2004 Elsevier B.V.
Tropical rainforests are among the most important biomes in terms of annual primary productivity and water cycling, However, the materials-exchange properties of Southeast Asian forests in their significant functions are less studied. We investigate key factors controlling materials-exchange, such as canopy (g,) and aerodynamic conductance (g.) and the decoupling coefficient (n) in an intact lowland mixed dipterocarp forest in Sarawak, Borneo. We operated an eddy covariance system above the canopy to measure canopy transpiration rate (E,) using an 80-m-tall canopy crane, and made concurrent meteorological measurements. In this region, solar radiation and air temperature have small seasonal variations, and annual rainfall is distributed evenly throughout the year, with some unpredictable intra-annual dry spells. We define three specific periods A, B and C as medium dry, heavy dry and wet periods, respectively, for analyses of the environmental control on E, according to their dryness level. The mean daily E, g, and D were higher in the wet period C than in the dry periods A and B. Also, each g, in its diurnal variation was much higher in the wet period C than in the dry periods A and B, where diurnal variations of g(c) were almost the same. Both the value of g, and its sensitivity to environmental variables were higher in the wet period C than in the dry periods A and B. The peak of n was higher in the wet period C than in the dry periods A and B because of a higher value of gc in period C. However, the higher values of gc in the wet period C did not cause a higher E, compared to in the dry periods A and B. (C) 2004 Elsevier B.V. All rights reserved.