Biogeographic Adaptation to Temperature, Photoperiod and CO2 in Boreal Conifers

9630241帝国北部地区的针叶林可能特别受到全球环境变化的影响。温度、光周期和二氧化碳水平可能相互作用，深刻影响树种的物候(季节发育时间)、净碳交换和生长。然而，对于任何给定的树种，来自不同地区的种群对全球变化的反应可能不同。迄今为止，在有关植被对全球变化的反应的科学研究中，这种可能性在很大程度上被忽视了。因此，我们不知道来自不同环境的种群是如何适应气候的，或者不同的种群是否会对温度或二氧化碳浓度的变化做出类似的反应。我们将在实验室和田间实验中探索这些问题，使用主要北方针叶树的不同种子来源：松树和云杉。我们将测试适应较冷环境的种群与适应较暖环境的种群对温度和二氧化碳水平变化的反应是否不同。有可能，生长在寒冷、紧张环境中的树木对全球变化的反应可能较弱，这可能会改变我们在全球变化下对北方生态系统进行全球建模的尝试。在受控环境研究中，树苗将在当前环境(360ppm)和未来更高的二氧化碳浓度(580ppm)下生长，并结合一定范围的温度和两个北温光周期。将对生长、物候、植物化学和生理学进行评估。实地研究将涉及北美中部几个地点跨越广泛气候梯度的较老、成熟的杰克松和黑云杉种群的广泛生物地理来源。实地测量将包括(从树木年轮)生长以及光合作用和呼吸速率的评估。建立枝条生长物候和呼吸作为组织氮和温度函数的模型，将能够比较苗木和成熟树的反应。这项研究将考察北方树木之间格局和机制的共性，改进碳交换模型，并加深我们对生物地理变化在植被对潜在全球变化响应中的作用的理解。

9630241 Reich The coniferous forests of boreal regions may be particularly affected by global environmental change. Temperature, photoperiod and CO2 levels may interact to profoundly influence the phenology (seasonal timing of development), net carbon exchange and growth of tree species. However, for any given tree species, populations from different regions may respond differently to global change. This possibility has been largely overlooked to date in scientific studies of vegetation response to global change. Thus, we do not understand how populations originating from diverse environments have adapted to climate, or whether diverse populations will respond similarly to altered temperature or CO2 concentrations. We will explore these issues in both laboratory and field experiments, using diverse seed sources of major boreal conifers: pine and spruce. We will test whether populations that are adapted to colder environments respond differently to altered temperature and CO2 levels than those from warmer environments. It is possible that trees originating in cold, stressed environments may be less responsive to global change, which could alter our attempts to globally model boreal ecosystems under global change. In controlled-environment studies, tree seedlings will be grown at present ambient (360 ppm) and future elevated (580 ppm) concentrations of CO2 in combination with a range of temperatures and two boreal photoperiods. Growth, phenology, and plant chemistry and physiology will be assessed. Field studies will involve plantations of older, mature jack pine and black spruce populations of broad biogeographic origin at several sites across a broad climate gradient in central North America. Field measures will include assessment of growth (from tree rings) and rates of photosynthesis and respiration. Development of models of shoot-growth phenology and of respiration as a function of tissue nitrogen and temperature will enable comparisons of seedling and mature tree responses . This research will examine the generality of patterns and mechanisms among boreal trees, improve models of carbon exchange, and increase our understanding of the role of biogeographic variation in vegetation response to potential global change.