元江干热河谷区橙子园蒸腾耗水机制研究

The water consumption mechanism by canopy transpiration under multiple environmental stress conditions is a difficult aspect of research in water-saving agriculture and plant drought-resistant physiology. The dry-hot valley region is characterized by low rainfall, strong evaporation and prominent water and heat conflicts. During the last stage of the dry season, the drought, hot and strong sunshine occur at the same, the stresses related to soil water, temperature and radiation, as well as their interactions make the transpiration mechanism extremely complicated. The dry-hot valley of Yuanjiang which is the site of the famous “Chucheng” orange planting base will be chosen as study area and orange orchard which is the typical economic forest in the region will be selected as study object in this research project. We plan to monitor the dynamics of trunk sap flow, environmental factors and other relevant indexes during the whole growth period of orange trees. Using these data, we intend to firstly explore the characteristics of canopy transpiration to indicate how orange trees cope with the dry-hot weather with multiple environmental stresses in the region by adjusting their transpiration. We secondly intend to study the response mechanism of transpiration to environmental factors systematically, demonstrate the relationships between transpiration and environmental factors, as well as the interactions of environmental factors. After, the main controlling factors of orange canopy transpiration will be identified and applied to construct canopy impedance sub-models with different complexity, which will be respectively nested into the Penman-Monteith model for transpiration simulation based on Bayesian analysis. Finally, the optimal transpiration model with proper parameters of the orange orchard will be determined considering the simulation accuracy, uncertainty and complexity of model structure. All these work are designed in order to reveal the canopy transpiration mechanism of orange orchard, thus providing theoretical basis for the rational and efficient irrigation schedule, as well as the water-saving regulation technology system for the orange economic plantation in the region.

多重环境胁迫条件对植物蒸腾耗水过程的影响机制是节水农业及植物抗旱生理领域的研究难点。干热河谷区降水较少但蒸发强烈，水热矛盾突出，旱季末期干旱与高温和强光并存，与水分、温度和辐射相关的多重环境胁迫及其交互效应共同作用，使得植物耗水机制异常复杂。本项目以著名的“褚橙”种植基地元江干热河谷区为研究区，以该区典型经济林橙子园为研究对象，拟通过对树干液流和环境因子等的动态监测，系统分析橙子园冠层蒸腾耗水规律，阐明干热季节里多重环境胁迫对蒸腾的影响；探究蒸腾与环境因子间的关系，及诸因子对蒸腾的交互作用和拮抗/协同原理，甄别耗水主控因子，并据此构建复杂程度不一的冠层阻抗子模型，结合Penman-Monteith模型和贝叶斯分析探索适宜的蒸腾估算模型及合理的参数化方案；最终揭示该区橙子园的蒸腾耗水机制，以期为制定科学合理的灌溉制度和高效的节水调控技术体系提供理论依据。

目前，环境胁迫对植物生命活动的限制研究主要集中于单一环境胁迫情况，植物对多重环境胁迫的适应研究较为缺乏，远不足以深入认识多重环境胁迫及其交互效应对蒸腾产生的复杂影响。干热河谷地区旱季和雨季交替，且旱季后期的干热阶段里干旱、高温、强光并存，在这种情况下，与水分、温度和辐射相关的胁迫以及它们之间的交互效应都可能会对树木的生长造成极端影响，使得植物的耗水机制异常复杂，具备研究多重环境胁迫对植物蒸腾耗水影响的绝佳条件。因此，本项目选择元江干热河谷地区典型经济林橙子园为研究对象，开展了如下工作：（1）对比研究了干季、干热季和雨季橙子园蒸腾变化特征，综合考虑不同天气和不同降雨类型的影响，对蒸腾日内变化动态和季节波动规律等方面进行了全面研究。（2）探究了环境因子对蒸腾耗水过程的驱动机制，厘清了环境因子对蒸腾的交互影响效应，明晰了诸因子对蒸腾强度的贡献大小，并定量区分直接贡献与间接贡献，判断出蒸腾的主控因子，揭示了蒸腾对其响应方式和敏感性，并获取了关键临界值。（3）构建出考虑环境因子交互影响的蒸腾模拟新模型，根据耗水主控因子的取舍形成不同复杂程度的模型结构；同时采用经典的基于环境因子影响相互独立假设的Jarvis-Stewart阶乘（JS）模型，模拟了橙子园蒸腾耗水量，通过改变阶乘因子数量及限制函数表达式形成不同复杂程度的模型结构；通过采用贝叶斯Bayesian方法率定和优化模型参数，筛选出最佳JS模型结构和最佳新模型结构，从模拟精度、输出不确定性、模型复杂度、过度拟合情况、蒸腾规律符合程度等方面综合评价，发现本研究所构建的新模型模拟效果优于经典的JS模型，为蒸腾模拟提供了重要的理论和方法参考。这些研究结果能为揭示完整的植物多重环境胁迫适应机制提供数据基础，也能为建立合理高效的节水灌溉技术体系和优化果园水分管理提供科学依据，因此具有重要的理论意义和应用价值。