珠江三角洲常见树种水分关系对城乡梯度环境变异的响应及调控机制

植物水分关系影响植物生长与存活，是理解树木响应和适应全球变化的关键。城市与周边乡村区域构成的城乡环境梯度能反映未来全球环境变化的趋势，是研究树木响应全球变化的“天然实验室”。本项目拟以珠江三角洲“城区-近郊-远郊-乡村”梯度上的6个常见树种为研究对象，测定一系列树木水力效率性状（叶片与枝条导水率）、水力安全性状（栓塞脆弱性、膨压丧失点、气孔控制能力）以及水力结构性状（胡伯尔值、纹孔、导管、叶脉、气孔等特征），结合叶片光合能力和年轮生长等重要功能性状，通过构建城乡梯度综合环境指标，定量分析植物水力性状与环境因子之间的关系，以期揭示珠三角地区常见树种水分关系对城乡梯度环境变异的响应规律及其调控机制，深入探究全球变化背景下树木的生理生态响应机理，为区域森林经营管理提供科学依据。

Plant water relations affect plant growth and survival, and consequently play a critical role in the response and adaptation of trees to global change. The environmental gradients across cities and their surrounding areas, which can represent future trend of global environmental change, have been recognized as “natural laboratories” for studying the responses of trees to global change. In this project, plant water relations of six common tree species distributed along an urban-rural transect in the Pearl River Delta will be investigated. Suites of functional traits related to hydraulic efficiency (i.e. leaf water conductance and branch water conductance), hydraulic safety (i.e. embolism vulnerability, turgor lose point, stomatal regulation) and hydraulic architecture (the Huber value, the anatomy and structure of pits, vessels, veins, and stomata) will be measured. In addition, leaf photosynthetic capacity and tree-ring growth related traits will also be determined. An Environmental Comprehensive Index will be calculated using the principal component analysis, and the correlations between plant hydraulic traits and environmental factors will be quantified using linear or nonlinear mixed effect models. The major objective of this project is to reveal the responses and regulatory mechanisms of plant water relations to environmental changes across the urban-rural gradients, for a better understanding of eco-physiological regulation of subtropical trees to global change scenarios.