亚热带代表性树种树干液流的径向分布格局及其机制研究

Transpiration is an important component of water balance of a forest ecosystem. Thermal techniques are generally engaged to measure the sap flow of single trees and then extrapolated to the transpiration of a forest ecosystem， while the radial variation of sap flow usually caused large error. In this study, the radial variation patterns of sap flow of Pinus massoniana and Schima superba will be studied using in-situ dying experiment and thermal dissipation probe (TDP) sap flow measurement. The seasonal variation and the environmental effect on the radial sap flow pattern will also be studied. In order to reveal the mechanism of radial variation patterns of sap flow, anatomical property of xylem cells will be analyzed with timber sampling and cut section observation method. The precision of TDP sap flow measurement will also be evaluated under different environment. The results of this study are expected to improve the accuracy of transpiration estimation of forest ecosystem with TDP method.

林木蒸腾是森林生态系统水分平衡的重要组分，通过热扩散技术测定单株树木液流进而推算林木蒸腾耗水是目前最主要的测定方法之一。但是由于树干液流径向分布不均以及探针长度与边材宽度不一致等原因，利用热技术估算林木蒸腾的精度显著降低。本研究在已有研究的基础上，利用热扩散技术和原位染色方法，通过野外原位监测，结合木材导水结构切片的室内分析，研究亚热带代表树种马尾松和木荷树干液流的径向分布格局，分析树干液流径向分布格局的时间动态规律，揭示影响液流径向分布格局的环境因子和内在机制。同时，评估探针法测定单木及林分蒸腾耗水结果的精度，并提出可能的修正方法。