Integration of Canopy and Hydraulic Architecture in Neotropical Shrubs Along Light and Moisture Gradients

9604424 Pearcy本研究将研究植物树冠的水力学与树冠上用于捕获光线的叶面积的数量和排列之间的相互关系，研究对象是一种著名的灌木属——精神病属（Psychotria）。基本假设是，在最大限度地捕获光和提供足够的茎导电性以向叶片供水之间存在权衡，而适应干旱地区的物种和适应或多或少永久潮湿地区的物种之间的权衡是不同的。被利用的物种沿着光照和鱼苗季节严重程度的栖息地梯度发生，因此水力学与光照捕获的选择压力在它们之间会有所不同。一个可以重建植物三维结构的计算机模拟模型将被用来估计不同物种的冠结构的光捕获能力和效率。将决定茎部的水力导度和对空化的脆弱性，空化是木质部中形成的气泡，阻碍水流并可能导致茎部死亡。最后，茎杆水力导度将被映射到树冠结构上，并用于模拟，以探索不同干旱情景下物种差异对空化脆弱性的影响。该研究将揭示物种差异最明显的表现形式冠的功能形态与物种沿光照和湿度梯度分布的关系。由于光照和湿度梯度是热带森林生物多样性的重要决定因素，该研究将最终为这些森林生物多样性的功能控制提供见解。

9604424 Pearcy This research will investigate the interrelationships between the hydraulics of a plant crown, and the amount and arrangement of leaf area on that crown that functions for light capture using the in species of the genus Psychotria, a prominent genus of shrubs. The basic hypothesis is that there is a tradeoff between maximizing light capture and providing sufficient stem conductivity to supply water to the leaves and that this tradeoff differs between species adapted to areas subject to drought and species adapted to areas more or less permanently wet. The species to be utilized occur along habitat gradients of light and fry season severity so that the selective pressures for hydraulics versus light capture will differ among them. A computer simulation model that can reconstruct the three-dimensional architecture of a plant will be used to estimate the light capture capacity and efficiency of the crown architectures of the different species. The stem hydraulic conductances and the vulnerability to cavitation, which is the formation of air bubbles in the xylem that blocks water flow and can lead to death of the shoot, will be determined. Finally, stem hydraulic conductances will be mapped onto the crown architectures and used in the simulations to explore the consequences of species differences in the vulnerability to cavitation under different drought scenarios. This research will provide insight into how the functional morphology of the crowns, the most visible manifestation of species differences, relates to species distribution along light and moisture gradients. Since light and moisture gradients are important determinants of biodiversity in tropical forests the research will ultimately provide insight into the functional controls on biodiversity in these forests.