滇东岩溶高原峰林湖盆水源枯竭机制研究

The Puzhehei peak forest -lake basin in the eastern of Yunnan karst plateau is a typical, subtropical peak cluster-depressions water sources in the south-western karst area of China. Effected by extremely arid climate since 2009, the water of the Puzhehei peak forest -lake basin has dried up, which is the worst drought-stricken area in Yunnan karst plateau. This project bases on the hypothesis, "there is a synergistic relation between vegetation restoration and strengthening management and storage of aquifer in karst water sources; the exhaustion of water source is a final result of failing self-management of the aquifer which is led by vegetation degradation". The study on the mechanism of water exhaustion of peak forest -lake basin is also based on a combined method of hydrological observation, hydrogen and oxygen stable isotope and hydrochemistry tracing. This paper reveals the function of water conservation of vegetation and its affections to runoff producing through simultaneous observation of vertical and horizontal structure of water behavior and distribution of precipitation. It also reveals that the source, storage and conversion process of water in its source, as well as the process in which the runoffs of water source are affected by vegetation patterns according to stable isotope of aquifer and changes of hydrochemistry abundance. This project will be helpful to the study of the present mechanism of water exhaustion in Yunnan karst plateau, and to the evaluation of vegetation restoration. And hopefully, it could inspire other scholars to study the universal topics of climate change and sustainability of karst ecosystem.

滇东岩溶高原普者黑峰林湖盆是西南岩溶区典型的亚热带蓄水型峰丛-洼地水源地，受2009年连年极端气象干旱影响，普者黑峰林湖盆水源枯竭，是云南岩溶高原受干旱影响最为严重地区。本项目基于"植被恢复与岩溶水源地含水结构层调蓄功能增强之间存在协同效应；水源枯竭是植被退化导致含水层水分自调节功能衰竭的体现"的假设，基于水文观测、稳定氢氧同位素与水化学示踪的综合研究方案，开展普者黑峰林湖盆水源地水源枯竭机制研究。依据水源地垂直结构层和水平结构的水分行为和降水分配同步观测，揭示植被水源涵养功能及其对产流的影响；依据含水层稳定同位素和水化学丰度变化信息，揭示水源地水分来源、存储和转化过程以及植被格局对水源地产流的影响过程。项目研究不仅有助于认识当前云南岩溶高原水源枯竭机制，评价植被恢复效果，制定应对干旱对策，还可为探究"气候变化与岩溶生态系统可持续利用"这一全球科学命题提供绝佳的研究切入点。

本项目在滇东岩溶高原普者黑峰林湖盆开展了生态水文过程观测、稳定氢氧碳同位素与水化学示踪的综合研究，并取得了以下认识：.1. 1980s以来的生态恢复政策实施、1990s开始的旅游开发是普者黑峰林湖盆土地利用/覆被变化的主要驱动力。流域降雨-径流相关性高，地表径流量主要受降雨量的影响。半分布式水文模型模拟表明，流域雨季径流属“雨养”型补给，旱季径流属“泉养”型补给。.2. 植被恢复可以影响降水在表层带产水功能结构层的垂向分配，从而影响植被水源涵养。峰林湖盆年产流54.22mm，占年降雨量的4.37%。清香木次生林表层带产流量高（17.04mm，占降雨量的1.37%）且历时长（8个月），年降雨地下漏失量为322.50mm（占年降雨量的26.77%），远小于云南松人工纯林（年降雨地下漏失量为644.59mm，占年降雨量的51.96%）。植被恢复促进表层带产水结构功能层的发育进而增强水源涵养功能，但能否增加局地降水水汽进而增加局地降水量，有待进一步观测验证。.3. 稳定氢氧碳同位素可以有效示踪降水在表层岩溶带产水功能结构层的分配过程，量化植物水分利用来源和比例。峰林湖盆降水线方程为 δD = 7.914δ18O + 13.101，显示降水水汽来源具有多源性。表层带地下水是旱季植物的稳定利用水源。植被恢复将减少对表层带地下水的利用比例转而利用土壤水。旱季清香木次生林植物主要利用中深层土壤水（62.21%），对表层带地下水利用比例低（14.45%），有利于涵养表层岩溶水。.4. 植被退化和人为干扰导致岩溶产水结构功能层瓦解，是普者黑峰林湖盆水源枯竭的主要原因。适配的水源林（适合的植物类型，适宜的森林面积，适当的位置）可以增强水源涵养功能以及改善水分增加条件。选择水分利用效率高的清香木次生林、云南松与清香木次生林优势树种（清香木、滇青冈、黄连木、锥连栎等）的混交林是普者黑峰林湖盆水源涵养功能恢复的优选水源林组合。