Transpiration and stomatal conductance in a young secondary tropical montane forest: contrasts between native trees and invasive understorey shrubs
Transpiration and stomatal conductance in a young secondary tropical montane forest: contrasts between native trees and invasive understorey shrubs
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DOI：
10.1093/treephys/tpy004
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发表时间：
2018-07-01
期刊：
影响因子：
4
通讯作者：
van Meerveld, H. J. (Ilja)
中科院分区：
文献类型：
--
作者：
Ghimire, Chandra Prasad;Bruijnzeel, L. Adrian;van Meerveld, H. J. (Ilja)
有人认为，旺盛的热带次生林可以有很高的蒸腾速率，但在这些森林中的树木和灌木的液流和气孔导度动态研究不足。为了解决这一知识差距，树干液流（热耗散法，12棵树）和气孔导度（气孔测定法，6棵树）测定年轻（5-7年）Psiadia altissima（DC。）公鸭树，一个广泛发生的物种占主导地位的年轻再生后，放弃了在马达加斯加东部高地的swidden农业。此外，还测定了两种常见入侵灌木马缨丹（Lantana camara L.）和Rubus moluccanus L.）在三个不同时期的土壤水分条件。三个调查物种的gs值显着较高，更敏感的气候条件下，在潮湿的时期相比，干燥的时期。林下灌木的gs对土壤含水量的敏感性远大于乔木。树蒸腾速率（E-C）是相对稳定的，在旱季，只有在旱季结束时受到土壤含水量的影响，这表明树木继续获得土壤水分，尽管干燥的表土。EC与水汽压亏缺（VPD）呈平台状关系，这是由于气孔关闭在高VPD。蒸汽压赤字是在Ec的变化的主要驱动力，在潮湿和干燥的季节。总体用水量的树木是温和的，可能反映低网站的肥力后，三个swidden种植周期。观测到的树木和灌木对土壤水分和气候条件的响应存在明显的差异，这强调了在对再生热带森林的蒸腾作用进行建模时，需要考虑根系分布。
It has been suggested that vigorous secondary tropical forests can have very high transpiration rates, but sap flow and stomatal conductance dynamics of trees and shrubs in these forests are understudied. In an effort to address this knowledge gap, sap flow (thermal dissipation method, 12 trees) and stomatal conductance (porometry, six trees) were measured for young (5-7 years) Psiadia altissima (DC.) Drake trees, a widely occurring species dominating young regrowth following abandonment of swidden agriculture in upland eastern Madagascar. In addition, stomatal conductance (g(s)) was determined for three individuals of two locally common invasive shrubs (Lantana camara L. and Rubus moluccanus L.) during three periods with contrasting soil moisture conditions. Values of gs for the three investigated species were significantly higher and more sensitive to climatic conditions during the wet period compared with the dry period. Further, gs of the understorey shrubs was much more sensitive to soil moisture content than that of the trees. Tree transpiration rates (E-c) were relatively stable during the dry season and were only affected somewhat by soil water content at the end of the dry season, suggesting the trees had continued access to soil water despite drying out of the topsoil. The Ec exhibited a plateau-shaped relation with vapour pressure deficit (VPD), which was attributed to stomatal closure at high VPD. Vapour pressure deficit was the major driver of variation in Ec, during both the wet and the dry season. Overall water use of the trees was modest, possibly reflecting low site fertility after three swidden cultivation cycles. The observed contrast in gs response to soil water and climatic conditions for the trees and shrubs underscores the need to take root distributions into account when modelling transpiration from regenerating tropical forests.