生态脆弱带大型矿区煤田开采后水循环变化及植被响应机制

About 90% of coal resources in China are distributed in the semi-arid north area, where water resource is poor and vegetation coverage is low. Coal-mining could cause the groundwater falling and the change of water cycle, thus resulting in vegetation degeneration. However, now there is lack of research on the scientific issues on relationship of water and soil environments, such as interaction between soil and ground water, response of vegetation on the change of water cycle, under the condition of coal exploitation in the semi-arid coal mining area of the vulnerable ecotone. Therefore, it is necessary to focus on those issues by the new methods and techniques. In this study, we aim at the ecological issues such as groundwater falling and vegetation degeneration in Shenfu coal-mining area, use the stable isotope techniques and principles to analyze the relationship of rainfall, soil water and groundwater under the different land uses, study the change process of water cycle due to groundwater falling, determine the source of water found in typical local plants (for example, Artemisia desertorum, Salix psammophila, Caragana korshinskii and Populus simonii), trace the response mechanism of vegetation on the change of water cycle and forecast the patterns of vegetation succession. The purpose of the study is to determine if groundwater is used by plants and to provide scientific foundations about water sources essential for vegetation recovery and sustainable development of water recources in Shenfu coal-ming area of the vulnerable ecotone.

地下水与植被之间关系复杂，涉及地下水、土壤、植被等相互之间的动态平衡；我国90%的煤炭资源分布在干旱半干旱区，区内水土流失严重，植被覆盖率低，水资源匮乏，生态系统稳定性差，煤田开采引起地下水埋深的变化直接影响植被的生长发育，导致植被退化。因此，结合矿区水资源不足的特点，开展地下水和植被相互关系的研究，对合理利用水资源及矿区植被恢复、促进煤炭资源生产持续发展具有重要意义。本项目针对煤田开采后出现的生态问题，选取生态脆弱带神府矿区为研究范围，以区内广泛分布的代表性植物为研究对象，利用氢氧稳定性同位素方法确定植被对不同来源水分的利用程度和利用方式，明确地下水对植被生长的影响权重，重点研究地下水水位下降对植被及其生长环境的影响，探索原有植被退化后植物种群的恢复机制和演替趋势，为矿区植被重建和永续发展提供科学的水分来源依据，也为我国煤炭资源的可持续开发提供科学参考。

针对黄土高原北部水土流失严重、植被生长不良、水资源匮乏以及地下水变化对植被的潜在影响等生态问题，本研究以黄土高原半干旱区六道沟小流域为研究区，以区内广泛分布的乔木种小叶杨和旱柳以及灌木种柠条、沙柳和沙蒿为主要研究对象，利用稳定同位素（δ2H、δ18O和δ13C）和植物生理参数分析流域内不同植被的水分来源、水分利用效率及共生策略；并通过测定不同移动性的土壤水（土壤水、土壤移动水、土壤束缚水）、地下水、植物根系水、茎木质部水同位素组成，示踪水分通过土壤剖面的轨迹及土壤水分运动过程，分析研究区降水-土壤水-地下水之间的转化关系以及地下水的补给过程，量化共生物种的水分生态位宽度与水分生态位重叠值，从而明确共生物种间的水分竞争关系以及个体水分生态位与群落生态位的关系，揭示共生植物的生态位分化机理。主要取得如下成果：（1）明确了研究区各水文要素的稳定性同位素时空变化特征，并建立了区域大气降水线、土壤水线和植物水线；（2）揭示了研究区造林先锋植物种的水分利用策略及共生机制；（3）明晰了研究区降水-土壤水-地下水之间的转化关系以及地下水的补给过程。这些成果对黄土高原北部矿区植被重建中植物种的选择提供了重要的科学依据，确定了不同物种的水分利用策略和地下水对特定物种的潜在影响，为研究区生态修复和植被的永续发展提供了科学的水分来源依据。