荒漠绿洲植被生态需水量化及其机理研究—以民勤县为例

Aiming at imperfect connotation, simple calculating methods and unfaithful quantifying results in previous researches on vegetational ecological water requirement leading to weak practicability of the findings, the oasis vegetation and the phreatic water, soil, plant, and atmosphere continuum (GSPAC) can be seen as a complex system by applying the system engineering idea and the vegetational ecological water requirement quantifying and its mechanism can be analyzed from complexity point. Firstly, the discerning index system of fitting extent under different vegetation types as well as hydrological and ecological conditions which are scientific and reasonable is to be established to reveal the connotation and driving force of oasis vegetational ecological water requirements. Then, the appropriate calculating method can be put forward by analyzing the key factors restraining calculating methods of vegetational ecological water requirements. Next, the response function of soil water and its movement flux to phreatic evaporation as well as quantitative relationship among hydrological components within GSPAC can be established to uncover the veil of the mechanism in vegetational ecological water requirements. Finally, the guarantee strategy for ecological water use safety is to be proposed by determining the critical threshold values of dynamic response of ecological water requirements to oasis characteristic parameters and the reasonable water resource utilization and protection pattern is to be presented by analyzing the comprehensive benefits of oasis water resource utilization. The results have great theoretical and practical significance for perfecting related ecological water requirement theory, solving such problems restricting agricultural development in Minqin county like the unreasonable water resource utilization, etc, and accelerating the construction for guaranteeing ecological water use safety as well as remitting desertification in Minqin county.

针对以往研究植被生态需水内涵不完善、估算方法单一、生态需水量化结果不准确，导致研究成果实用性差等问题，运用系统工程思想，将绿洲植被与潜水-土壤-植物-大气连续体（GSPAC系统）视为一个复合系统，从复杂性视角研究植被生态需水量化及其机理。构建科学合理的植被类型和水文生态条件适宜程度识别指标体系，揭示绿洲植被生态需水的内涵和驱动机制；分析生态需水估算方法的关键约束因子，提出适宜的生态需水估算定量公式；建立土壤水分及其运动通量对潜水蒸发的响应函数关系及GSPAC系统各水文要素间的定量关系，揭示植被生态需水机理；确定植被生态需水对绿洲特征参数动态响应的临界阈值，提出生态用水安全保障策略；分析绿洲水资源利用综合效益，提出水资源合理利用与保护模式。研究成果对丰富和完善生态需水相关理论，解决民勤县水资源利用不合理等诸多制约农业发展的问题，促进民勤生态用水安全保障建设和缓解荒漠化具有重要理论和实践意义。

针对以往研究植被生态需水内涵不完善、估算方法单一、生态需水量化结果不准确，研究成果实用性差等问题，运用系统工程思想，将植被与潜水-土壤-植物-大气连续体（GSPAC系统）视为复合系统，从复杂性视角研究民勤绿洲植被生态需水量化及其机理，对丰富和完善生态需水理论，解决民勤水资源利用不合理等诸多制约农业发展问题，促进民勤生态用水安全保障建设和缓解荒漠化具有重要理论和实践意义。主要研究结果如下：.（1）运用综合指标法构建了民勤绿洲生态系统适宜程度识别指标体系，并对2010-2015年生态系统适宜性进行综合评价。结果表明，适宜程度从2010年低分值不适宜程度过渡到2013年稳定程度再到2015年低分值较适宜程度，综合得分增长率高峰分别为2012年的25.41%和2014年的22.61%，2015年增速放缓，增长率下降为6.88%。各指标层分析发现，水文水资源对生态适宜程度影响最大，其次为生态建设。.（2）基于改进的间接计算方法建立植被系数K的二阶Gaussian模型，并运用灰色模型 GM(1，1)对民勤县生态需水量进行预测。结果表明，优化所得潜水蒸发量—埋深曲线对实测数据拟合度更好，植被系数取值更精确，计算所得2015年民勤绿洲各类植被面积与资料记载差异较小，生态需水量与FAO推荐使用的Penman－Monteith模型结果间无显著差异，预测2020年民勤天然植被生态需水总量为4060.8×104 m3，其中天然林地3100.1×104 m3，天然草地960.7×104 m3。.（3）运用多元回归统计方法进行地下水埋深分析和预测，通过逐步回归模型剔除对地下水埋深影响不显著的因素，确定最优回归方程为Y=24.980-0.557 X8+0.228 X4-0.109 X10（X8为地下水开采量，X4为上游来水量，X10为人口数），X8、X4、X10是影响地下水埋深的主要因素，且X8为主导因子，此方程可对民勤绿洲地下水埋深进行有效预测。.（4）运用生态足迹模型对民勤县2007-2018年水资源可持续利用分析结果表明，民勤水资源利用呈不可持续状态，水资源生态足迹中农业占比最大但用水效率最低，水资源供需矛盾加剧；农业生态足迹与城市化率呈负相关，相关系数为0.78，城市化率提高能明显降低农业生态足迹。因此，改变产业结构、提高水资源利用效率、增强水利设施建设是民勤水资源可持续利用的基本途径。