Resource Allocation and Allometry of Plant Growth in the Arctic: Key Constraints on Change and Predictability of the Arctic System

这项拟议的研究将通过提高我们对北极地区植被变化和植被功能的广泛模式的理解，为北极系统科学计划的主要主题做出贡献。基本的假设是，对北极环境的进化适应限制了北极植物的生长模式(即它们的资源分配模式和生长异速生长)，而这些适应反过来在调节北极植被的变化和复原力及其对北极系统的反馈方面发挥了重要作用。这项拟议的研究基本上是为了寻找植物生长、资源分配和异速生长的一般特征，这些特征可以用来开发对植被特性和北极植被在北极系统中的作用的大规模、长期预测。通过比较广泛分布的地点的各种植被类型，这项研究还将有助于确定不同植被类型、植物功能类型和物种对气候变化和其他形式干扰的相对脆弱性。研究地点包括阿拉斯加的图利克湖、瑞典的阿比斯科、斯瓦尔巴群岛的纽阿勒松和格陵兰岛的扎肯伯格。要评估的植物变量--初级生产力、碳通量、N周转、NDVI和冠层结构--都是陆地景观与北极系统能量、水和元素循环之间的反馈和相互作用的关键组成部分。每个地点的实地研究将包括用于分析生产-生物量关系、生物量分配模式、氮素周转和使用以及冠层叶面积-叶氮交互作用的样方收获。额外的采样将把这些变量与二氧化碳通量、茎密度和分枝模式以及NDVI联系起来。冬季访问将确定树干和树冠结构对雪和冬季小气候的影响。除了对结果进行实证分析外，这项研究的一个成果将是一个数据库，用于对整个北极地区的植被特性和过程进行建模和外推。与老牌建模团队的长期合作将继续下去。这里更广泛关注的主要问题是(1)从单一地点和物种到更大的区域环境系统的生态理解的尺度，(2)单个物种或植物“功能类型”对整个生态系统和景观水平过程的影响，以及(3)在不断变化的世界中生态系统和景观的抵抗力、弹性和稳定性的意义和衡量。这些问题的解决是制定保护和管理各地生态系统和景观的健全政策的关键。拟议的研究还将通过继续长期参与培训REU本科生、博士后研究员、技术人员和科学记者，为未来专业人员和普通公众的教育做出几项贡献。

The proposed research will contribute to the main themes of the Arctic System Science program by improving our understanding of the broad patterns of vegetation change and vegetation function across the Arctic. The underlying hypothesis is that evolutionary adaptation to the arctic environment places constraints on the patterns of growth of arctic plants (i.e., on their resource allocation patterns and allometry of growth), and that these adaptations in turn play an important role in regulating change and resilience in arctic vegetation and its feedbacks to the Arctic System. The proposed research is designed essentially as a search for the general characteristics of plant growth, resource allocation, and allometry that can be used to develop large-scale, long-term predictions of vegetation properties and of the role of arctic vegetation in the Arctic System. By comparing a wide range of vegetation types in widely-separated sites, the research will also help to identify the relative vulnerability of different vegetation types, plant functional types, and species to climate change and other forms of disturbance. The research sites include Toolik Lake, Alaska; Abisko, Sweden; Ny Alesund, Svalbard; and Zackenberg, Greenland. The plant variables to be evaluated--primary production, C fluxes, N turnover, NDVI, and canopy structure--are all key components of the feedbacks and interactions between the terrestrial landscape and the cycles of energy, water, and elements in the Arctic System. Field research at each site will include quadrat harvests for analysis of production-biomass relationships, biomass allocation patterns, N turnover and use, and canopy leaf area-leaf N interactions. Additional sampling will relate these variables to CO2 fluxes, stem density and branching patterns, and NDVI. Winter visits will determine effects of stem and canopy structure on snow and winter microclimate. In addition to empirical analysis of results, one product of the research will be a data base for modeling and extrapolation of vegetation properties and processes across the Arctic region. Long running collaborations with established modeling groups will continue. The major issues of broader interest here are (1) the scaling of ecological understanding from single sites and species to larger, regional environmental systems, (2) the effects of individual species or plant "functional types" on overall ecosystem and landscape-level processes, and (3) the meaning and measurement of resistance, resilience, and stability of ecosystems and landscapes in a world of constant change. Resolution of these issues is key to development of sound policies on conservation and management of ecosystems and landscapes everywhere. The proposed research will also make several contributions to education of future professionals and of the general public, by continuing our long-term involvement with training of undergraduate REU students, postdoctoral fellows, technicians, and science journalists.