Canopy Structure and CO2 Exchange of Arctic Vegetation: Key Constraints on Change and Predictability of the Arctic System

这项研究将通过研究北极植被冠层结构、氮分配和全系统CO2通量与生态系统呼吸及其主要组成部分、植物和土壤呼吸之间的关系，提高对整个北极植被功能广泛模式的认识。这项研究是对植被功能、资源分配和异速生长的一般特征的研究的一部分，这些特征可用于对植被和生态系统特性以及北极生态系统在北极系统中的作用进行大规模、长期的预测。计划进行研究的地点包括阿拉斯加的图里克湖和巴罗、西伯利亚的切尔斯基、格陵兰的图勒，可能还包括加拿大北方的地点。每个地点的实地研究将包括测量不同植被中CO2通量的光响应（净生态系统交换，NEE;总初级生产量，GPP;生态系统呼吸，RE;自养呼吸，RA，异养呼吸，RH）。要评估的植被和土壤变量-冠层光合面积及其氮含量、归一化植被指数、土壤碳和氮含量以及冠层空气和土壤温度等小气候变量-都是调节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。待检验的核心假设是：1。在整个北极地区，冠层氮含量将是一个更好的整体预测NEE和GPP比叶面积，因为叶氮浓度将增加在较高，较冷的纬度，导致较高的GPP每单位叶面积与纬度，但类似的GPP每单位叶N.2。从长期来看，RE、RA和RH都必须与GPP及其控制有关，因为GPP决定了生态系统的总C输入。在短期内，RA和RH将对环境变化做出不同的反应：RA将与相对快速的气温变化最密切相关，而RH将变化较慢，并与土壤温度和湿度等变化较慢的变量相关。和RE将测试我们在北极地区从一个地点外推到另一个地点的能力，并将有助于确定是否可以为整个北极开发一个单一的模型参数化。一个关键产品将是一个数据库，用于模拟和推断整个北极地区的植被特性和二氧化碳通量。

This research will improve understanding of the broad patterns of vegetation function across the Arctic through research on the relationships among arctic vegetation canopy structure, N allocation, and whole-system CO2 fluxes, and ecosystem respiration and its main components, plant and soil respiration. The research is part of a search for the general characteristics of vegetation function, resource allocation, and allometry that can be used to develop large-scale, long-term predictions of vegetation and ecosystem properties and of the role of arctic ecosystems in the arctic system.Sites planned for research include Toolik Lake and Barrow, Alaska; Cherskii, Siberia; Thule, Greenland; and perhaps sites in northern Canada. Field research at each site will include measurements of the light response of CO2 flux in diverse vegetation (Net Ecosystem Exchange, NEE; Gross Primary Production, GPP; Ecosystem Respiration, RE; Autotrophic Respiration, RA, Heterotrophic Respiration, RH). The vegetation and soil variables to be evaluated--canopy photosynthetic area and its N content, NDVI, soil C and N content, and microclimatic variables like canopy air and soil temperatures--are all key components of regulation of the feedbacks and interactions between the terrestrial landscape and the cycles of energy, water, and elements in the arctic system. The core hypotheses to be tested are:1. Over the entire arctic region, canopy N content will be a better overall predictor of NEE and GPP than leaf area because leaf N concentrations will increase in higher, colder latitudes, leading to higher GPP per unit leaf area with latitude but similar GPP per unit leaf N.2. In the long term RE, RA, and RH must all be related to GPP and its controls because GPP determines the total C inputs to the ecosystem. In the short term, RA, and RH will respond differently to environmental variation: RA will be most closely correlated with relatively rapid changes in air temperature while RH will change more slowly and in correlation with more slowly-changing variables like soil temperature and moistureIn addition to empirical analysis of results, modeling of NPP, GPP, and RE will test our ability to extrapolate from one site to another within the Arctic and will help to determine whether a single model parameterization can be developed for the entire Arctic. A key product will be a data base for modeling and extrapolation of vegetation properties and CO2 fluxes across the arctic region.