喀斯特坡地典型生境植物根区水分补给机制研究

水分供应能力是影响喀斯特地区植被恢复可持续性的关键因子之一，但复杂的岩土结构及其水分动态监测的困难，严重制约了地下储水介质持水能力与植物根区水分关系的认识。为深入了解不同岩土结构生境下植物根区水分的滞留时间与补给规律，本项目拟以水分环境差异明显的喀斯特坡地典型生境植物为对象，通过地球物理勘探，结合中子水分仪，掌握不同坡位岩土厚度分布和岩土剖面水分动态；在此基础上结合同位素示踪方法，尝试以植物枝条水同位素信号反映根区可利用水分的平均同位素组成的思路，量化植物根区水分滞留时间与补给动态；同时，综合根区土壤-表层岩溶带水分补给动态、根系分布、降水特征、植物水势等信息，多角度检验研究结果，阐明不同生境植物根区水分补给机制；基于根区水分补给过程，探明生态水文分离现象的机理；研究结果能为未来降水格局变化下植物对水分变化的响应策略的预测和植被恢复可持续发展的部署提供科学依据。

Water supply capacity is one of the key factors affecting the sustainability of vegetation restoration in karst areas. However, there exists complex rock-soil structures, and it is also difficult to monitor water dynamics in soil and epikarst zones, which limit the understanding of the interaction between water holding capacity of soil-epikarst zones and plants. For a deep understanding of the processes of residence time distribution and replenishment of water within the root zone under different rock-soil structures, in this proposal, the study site and plants will be selected in typical habitats of karst sloping land with diverse water conditions. The geophysical imaging methods will be used to detect the structure and depth distribution of soil and epikarst at different slope locations. Some neutron probes will be used to estimate variations of water content in soil-epikarst profiles. Based on isotope tracing technology, an idea that stable isotope signature of plant xylem water can reflect the average isotopic composition of the available water within the root zone will be proposed. Thus, isotopic composition of xylem water and rainwater will be used to quantify residence time distribution and replenishment of root-zone water. Meanwhile, an integrated analysis of water replenishment in soil-epikarst zones, root distribution, precipitation patterns and plant water potential will be used to examine the results, and to reveal the mechanism of root-zone water replenishment under different habitats. Then, we intend to reveal the occurrence mechanism of the ecohydrological separation phenomenon in karst environment via the process of root zone water replenishment. The related results achieved in this project will provide scientific grounds not only for anticipating how shifts in precipitation patterns will affect plant response strategies to water changes, but also for deploying a sustainable development of vegetation restoration in karst areas.