水文循环与生态过程的相互联系、相互影响是生态水文学研究的核心问题，是合理开发利用水资源和生态系统自然资源的理论基础，也是科学进行生态系统保护和修复、实现可持续发展的依据。本文对水分控制下的生态水文过程进行了研究，从机理上阐述了气候变化对生态水文过程的影响。首先，论文通过数据搜集，在中国东北样带中部的科尔沁沙地对生态水文最优性理论进行了验证和应用。结果表明在合理选择参数取值的情况下，该理论适用于所选研究地区，并且分析得到理论植被盖度和观测植被盖度的差异主要受到非生长季水量平衡余项影响。应用该理论在植被盖度和植被形态特征、气候因子之间建立了定量关系。其次，论文中用降雨特征参数表述降雨量变化，定量分析了降雨特征变化对植被盖度的影响。结果表明，随着降雨总量的增大，植被盖度增大；随着降雨频率的增大，植被盖度先增大后减小；非生长季长度越长，植被盖度对非生长季水分蓄变量相关参数越敏感。论文进而分析了不同植被类型潜在蒸腾需求对植被盖度的影响，发现潜在蒸腾能力不同的植被类型对不同的降雨特征变化的适应范围存在差异。将上述植被盖度与降雨之间的量化关系代入水量平衡方程，通过归因分析，可以区分降雨变化引起水量平衡变化的直接和间接贡献。再次，论文耦合随机土壤水模型建立了土壤-植被系统水-碳-氮循环模型，从土壤水对植被养分循环的控制角度阐述了水分条件对植被生长的影响。通过随机过程理论和统计分析，发现土壤-植被系统各碳、氮库物质之间存在显著相关关系。降雨通过改变土壤水从而影响各碳、氮库物质含量，随着降雨增加，植被碳、氮含量、土壤总含碳量增加，土壤有机含氮量和可溶性无机含氮量减少。论文最后综合水分条件对植被盖度和土壤-植被系统养分循环控制的理论和模型，在未来气候情景下模拟了中国东北样带的主要生态水文过程变化。结果表明：（1）不考虑蒸腾潜力变化，植被盖度在未来气候情景下增加；考虑蒸腾潜力变化，植被盖度在未来气候情景下变化不大；（2）根据未来气候情景改变降雨输入条件，土壤-植被系统除土壤总含碳量外，其他各库物质含量到2070年均达到新的平衡。
The link and interaction between hydrological and ecological processes are the key problem of ecohydrology. To rationally develop and utilize water resources and ecosystem natural resources should be based on the understanding of this problem. Also, it is the foundation of ecological protection and restoration as well as the realization of sustainable development. In this thesis, a study is conducted on water-controlled ecohydrological processes. The mechanism of how climate change influences ecohydrological processes is discussed.Through data collection, the ecohydrological optimality theory is firstly validated and applied in Horqin Sands in the middle of the Northeast China Transect (NECT). The results show that this theory can be conducted in this area very well with proper chosen parameter values. The difference between theoretical vegetation cover and observed one is mainly attributed to the effect of non-growing season water residue. Specific mathematical relationships between vegetation cover and vegetation morphological character, vegetation cover and climate factors are found through the application of the theory.Secondly, by describing total rainfall with rainfall property parameters, mathematical analyses are executed to detect the effects of rainfall properties on vegetation cover. The trend of vegetation cover to total rainfall, or rainfall intensity, is positive. With growing rainfall frequency, vegetation cover increases first and goes down after a peak. Longer non-growing season length makes vegetation cover more sensitive to parameters related to non-growing season water residue. A discussion that different transpiration potentials of plant types affect vegetation cover is also given. It is suggested that plants with different transpiration potential may adjust vegetation cover to adapt to rainfall pattern changes on different levels. Furthermore, the direct and indirect causes of water balance change by rainfall can be distinguished through substituting the mathematical relationship between vegetation cover and rainfall properties into the water balance equation, and then using attribution analysis approach.Thirdly, a nutrient cycle model of carbon and nitrogen in the soil-plant system is coupled with the stochastic soil moisture model in this thesis. The effect of water to plant growth is viewed from a water-controlled plant nutrient cycle perspective. By the means of stochastic process theory and statistic approach, significant correlation is found between the mass in each carbon or nitrogen pool with others in the soil-plant system. Rainfall variation influences the mass in carbon and nitrogen pools through changing soil moisture. With increasing rainfall, plant carbon and nitrogen pool and soil carbon pool grow. While Soil organic total nitrogen pool and dissolved inorganic nitrogen pool shrink.Finally, a comprehensive application of the theory and models of water control on vegetation cover and nutrient cycle is conducted to analyze how the key ecohydrological processes develop in future climate scenarios in NECT. The results show: (1) vegetation cover increases without considering the transpiration potential change with climate. If taking the change of transpiration potential with climate into account, vegetation cover changes little in future climate scenarios. (2) According to the rainfall scenarios in the future, all mass in soil-plant system carbon and nitrogen pools reach new steady states in 2070, except for soil total carbon.
