基于氢氧同位素的淡水湿地森林对水文过程调控机制——以安徽安庆湿地森林为例

Little information is available on how eco-hydrologic processes are regulated by freshwater wetland forest along the Yangtze River. Three types of planted forest: the coniferous forest of Taxodium ascendens, the broad-leaved forest of populous deltoides, and the mixed forest of populous deltoides, Liquidambar formosana and Taxodium ascendens in Xinzhou and Meicheng of Anqing region of Anhui Province along the Yangtze River will be studied. We will (1) determine the relationships among different water sources including precipitation, surface runoff, soil water, litter water, groundwater, evaporation water, and plant xylem water, (2) examine the water spatial distribution and movement in the soil profile under different intensity rainfall conditions, (3) assess the contributions of different intensity rainfall to soil water and plant xylem water, (4) determine the water use patterns of dominant plant species in freshwater wetland forest, and (5) clarify mechanisms for regulating hydrologic processes caused by different vegetation structures of freshwater wetland forest in combination with environmental factors, changes in water level, vegetation, and soil structure in Anqing region of Anhui Province along the Yangtze River, using a hydrogen and oxygen stable isotope technique in combination with multivariate linear mixed models. In theory and practice of ecology, it is important to innovatively and quantitatively investigate the water cycle patterns of wetland forest ecosystems and their response mechanism to different intensity rainfall conditions. This study will not only reveal regulation role for the effects of vegetation structures of freshwater wetland forest on hydrologic processes along the Yangtze River, but it will also provide scientific basis and evidence for managing and restoring freshwater wetland forest along the Yangtze River.

针对我国长江中下游淡水湿地森林对水文过程调控机制不清楚，本项目以安徽沿江地区（安庆新洲等）三个典型淡水湿地森林(池杉针叶林，美洲黑杨阔叶林，美洲黑杨-枫香-池杉针阔混交林）为研究对象, 利用氢氧稳定同位素示踪技术，结合多元线性混合模型等手段，确定大气降水、地表水、土壤水、枯枝落叶水、地下水、蒸发水和植物水的水分来源，定量阐明不同强度降水在土壤剖面中水分迁移规律及其对不同层位土壤水的贡献率，以及林中主要优势植物水分利用率和水分利用格局；结合环境因子、水位动态变化和植被、土壤结构等数据综合分析，从本质上揭示安徽沿江地区淡水湿地森林植被结构对水文过程的调控作用，创新和发展湿地森林生态系统水循环定量研究模式，为揭示长江中下游地区淡水湿地森林对水文过程的调控机理、湿地森林恢复重建、水资源管理及其对降水格局响应机制提供科学依据，具有重要的理论和实践意义。

针对我国长江中下游淡水湿地森林对水文过程调控机制不清楚，本项目以安徽沿江地区三个典型淡水湿地森林（池杉针叶林，美洲黑杨阔叶林，美洲黑杨-枫香-池杉针阔混交林）为研究对象，运用氢氧稳定同位素技术，结合多元线性混合模型和贝叶斯模型等手段，系统研究并确定了大气降水、地表水、枯枝落叶水、土壤水、地下水、蒸发水和植物水的水分来源，定量阐明不同量级降水在土壤剖面中水分迁移规律及其对不同层位土壤水的贡献率，以及林中主要优势植物水分利用率和水分利用格局。研究发现：小雨及中雨对三种淡水湿地森林土壤水的贡献率无显著差异，大雨对美洲黑杨-枫香-池杉针阔混交林土壤水贡献率（74.3%）显著高于池杉针叶林（66.9%）及美洲黑杨阔叶林（62.9%），表明混交林土壤截持强降水能力显著高于纯林。美洲黑杨与池杉及枫香混交后，对60～100cm深层土壤水的利用率减小，而对对0～40cm浅层土壤水利用率增加，这对由降水过量引起的洪涝灾害有一定的缓解作用。针阔混交林对水文过程调控作用优于纯林，具有更强的蓄洪防旱能力。建议今后在长江中下游地区进行退化淡水湿地森林植被恢复时，应注意多物种配置，以提高淡水湿地森林生态系统的水源涵养能力。本项目的理论和实践意义在于：从本质上揭示安徽安庆地区淡水湿地森林对水文过程的调控作用，创新和发展了淡水湿地森林生态系统水文过程定量研究模式，为揭示长江中下游地区淡水湿地森林对水文过程的调控机理、淡水湿地森林恢复重建、水资源科学管理及其对降水格局变化的相应机制提供科学依据。