森林植被影响岩溶水源地产水功能的观测研究

On the base of documents and field observation, the hypothesis was proposed that the suitable forest-vegetation landscape pattern with adequate area and proper locations has a function of water self maintaining-and-readjusting for watersheds water-production. The Bajiang river watersheds of the Shilin County of Yunnan center were proposed for the experiment. The observation of precipitation pattern has been designed on the analysis of topography and vegetation pattern there. Meanwhile, the observation of precipitation partitioning, vertical and horizontal, in the watershed has been also proposed together with the environmental isotope's tracing in order to analyze the water balance model among the rainfall, surface runoff, infiltration, soil water, epikarst well, discharges of the karsr spring and Bajiang river and its relationship to vegetation. The origin, storage, and seasonal distribution of the watershed water will be studied related to vegetations by the tracing results from the every water cycling point and vertical zones of the water resource lands. The impact of the vegetations on the water production function in the watersheds will be not only discussed with water balance, but also described with environmental isotope features. With combining the watershed precipitation pattern with water conservation in the watersheds' vertical zones, the mechanics will be systematically described that the forest-vegetations affect the watershed water production. And therefore, the theory and techniques will be summarized for identifying the forest pattern that is favorable to water production in the karst watersheds.

基于文献和调查资料分析，提出面积适宜、位置适当的适配森林植被格局对水源地具有"水分自养调节功能"的假设。选择云南中部石林巴江流域，开展地形、森林植被格局分析基础上的降雨格局观测实验，同步开展水源地垂直结构层和水平结构的降雨分配观测和环境同位素示踪，以获取实验流域的降雨、地表径流、入渗、土壤水分、表层带水位、岩溶泉（暗河）、巴江河流量的水平衡关系及与森林植被的关系；用流域水循环各个环节和水源地结构层含水介质的环境同位素示踪结果，分析水源地水分来源、储存、季节分配及与森林植被格局的关系；不仅有水量平衡揭示森林植被格局对水源地产流的影响，也有环境同位素信息揭示森林植被影响岩溶水源地产水功能的过程，将流域降雨格局与水源地垂直结构层水源涵养分析全面结合，系统阐述森林植被影响岩溶水源地产流的效应和机制，识别影响岩溶水源地产流的森林植被格局，构建促进岩溶流域水资源持续供给的森林植被格局的保护与修复技术。

以喀斯特地区关键性资源水土资源协同保育要求，开展影响水源地产流关键要素的配对观测，研究喀斯特水源地水源林保育时空格局，核心是水源地垂直涵养功能与水平格局増流效应的协同。在云南省石林县的巴江流域建立了植被演替系列的配对观测基地，观测水源地垂直结构层的降雨分配与降雨格局，在热带雨林区和中高山湿润常绿阔叶林水源区开展森林和裸地配对观测，弥补片断化、人工化、幼年化森林植被对降雨观测的影响。降雨受地形和植被协同影响，地带性植被高地区可增加30%以上的降雨；云南松林区降雨比降雨均值低约10%，与其温度高，风速低，干燥有关；喀斯特石漠化地降雨格局复杂；热带雨林的林内降雨和林外降雨对比关系不确定。喀斯特水源地水源涵养功能以地带性植被（滇青冈林）为好，完整水源涵养层次增加下渗、延长与稳定表层带水层厚度，增加流域产流。中小雨（日降雨≤20mm）多补充土壤水分；降雪最有利于增加水层厚度，大雨、暴雨影响地下水层厚度通过其他途径；水源地森林和土石界面影响产流。流域水量平衡以滇青冈林和次生林水源地产流多、持续时间长。模拟实验结果是裸地地表径流超过原生林地表径流41倍，原生林地持续渗透流时间是次生林地和裸地的1.1-1.8倍，裸地泥沙量超过原生林的190倍。原生林垂直渗透量是其水平径流的48倍以上，原生林根系、树干与土石界面能增加垂直渗透与泥沙下渗，但总量远低于裸地。因此，原生林不仅增强水源涵养，也能使水源地持续增强水源涵养功能。模拟分析表明，巴江流域上游增加水源区60%的林地面积，能降低15.5%洪峰流量，增加22%的产流，尤其是旱季；温度升高1.5℃会逐年降低产流，这是石漠化和云南松林区的现实。遥感信息分析表明，湖岸森林有助于湖泊湿地土壤水分保持。水源林水源涵养功能综合评价结果是滇青冈林（1.17）、云南松林（0.56）、落叶次生林（0.49）、灌丛（0.44）、草丛（0.43）。增强流域有效产流的水源林配置以水源区的高地、湖泊湿地的地带性植被（半湿润常绿阔叶林，如滇青冈林）为目标群落，改善现有森林格局，即增强降水的水源涵养，又增加局地降雨，实现流域产流的“削峰补枯增量”。在石林巴江流域区，要将石漠化治理、乡土生物多样性保护恢复、发展特色产业与保育水源林相融合，以巴江流域上游高地（溶丘）、湿地的次生植被、云南松林、石漠化区为水源林优先保育改造区，石林世界地质公园要优先实施。