Linkage between seasonal photosynthesis and hydraulic acclimation of different paper birch populations in Canada

纸桦(Betula Papyrifera Marsh.)是加拿大北部针叶林中最重要的商业阔叶木树种之一。它的经济重要性在未来可能会增加，因为它被用来生产单板和家具等增值木制品。它也是北方阔叶-针叶混交林的重要生态成分。桦树种群在生长、形态和耐旱性方面存在相当大的遗传差异。然而，很少有研究集中于单一物种在广泛环境条件下的变异性。例如，水分运输机制的遗传可塑性将是允许物种适应更干燥的生境的一个因素。正如世界各地专家预测的那样，我们北方的气候将变得更加温暖和干燥。这种气候变化肯定会影响我们的森林生态系统，比如落叶针叶树和常绿针叶树之间的关系。了解纸质白桦树对气温升高、生长季节延长和更干燥的环境的反应，可以增强我们预测纸质白桦树将如何应对气候变化的能力。水力特性，即植物将水分从土壤输送到树叶的能力，在决定植物如何响应水分供应和设定最大气体交换速率方面都是重要的。在拟议的项目中，我将使用一个常见的花园实验，主要沿着水分梯度种植来自不同生境的纸质桦树，以检查不同桦树种群的水分关系。同时，我将通过一个温室实验，通过控制土壤水分和大气二氧化碳浓度来考察不同的桦树种群对水分胁迫和二氧化碳增加的反应。在田间和温室试验中，我将在整个生长季节测量桦树茎的导水率、叶片的光合作用速率。在营林实践中，这些知识将为更好地管理加拿大北部和落叶地区的纸桦/针叶混交林提供指导。

Paper birch (Betula papyrifera Marsh.) is one of the commercially most important hardwood species in Canada's boreal forests. Its economic importance may increase in the future as it is used to produce value-added wood products such as veneer and furniture. It is also an ecologically important component of boreal broadleaf-conifer mixture. There are considerable genetic variations among birch populations for growth, morphology and drought tolerance. However, few studies have focused on the variability within a single species over a broad range of environmental conditions. For example, genetic plasticity of water transporting mechanism would be a factor that permits the species adaptation to drier habitats. As predicted by experts around the world, our boreal climate will become warmer and drier. This climatic change will definitely affect our forest ecosystem, such as the relationship between deciduous and evergreen conifers. Understanding the responses of paper birch trees to increased air temperature, prolonged growing season and a drier environment can strengthen our ability to predict how paper birch will respond to climate change. Hydraulic properties, or the capabilities of plants to transport water from soil to leaves, are important both in determining how plants respond to water availability and in setting maximum rate of gas exchange. In the proposed project I will use a common garden experiment planting paper birch trees from different habitats mainly along a moisture gradient to examine water relationships of different birch populations. At the same time I will use a greenhouse experiment by controlling soil moisture and atmospheric CO2 concentration to examine how different birch populations respond to water stress and increased CO2. In both field and greenhouse experiments I will measure birch stem hydraulic conductivity, leaf photosynthetic rate throughout the growing season. In silvicultural practice, the knowledge will provide a guide for the better management of paper birch/conifer mixed-species forests in the Canadian boreal and deciduous regions.