Department of Ecology and Evolutionary Biology, University of Colorado, Boulder, CO 80309, USA.
New Phytol. 2010 Mar;185(4):1000-15. doi: 10.1111/j.1469-8137.2009.03154.x. Epub 2010 Jan 19.
*Understanding controls over plant-atmosphere CO(2) exchange is important for quantifying carbon budgets across a range of spatial and temporal scales. In this study, we used a simple approach to estimate whole-tree CO(2) assimilation rate (A(Tree)) in a subalpine forest ecosystem. *We analysed the carbon isotope ratio (delta(13)C) of extracted needle sugars and combined it with the daytime leaf-to-air vapor pressure deficit to estimate tree water-use efficiency (WUE). The estimated WUE was then combined with observations of tree transpiration rate (E) using sap flow techniques to estimate A(Tree). Estimates of A(Tree) for the three dominant tree species in the forest were combined with species distribution and tree size to estimate and gross primary productivity (GPP) using an ecosystem process model. *A sensitivity analysis showed that estimates of A(Tree) were more sensitive to dynamics in E than delta(13)C. At the ecosystem scale, the abundance of lodgepole pine trees influenced seasonal dynamics in GPP considerably more than Engelmann spruce and subalpine fir because of its greater sensitivity of E to seasonal climate variation. *The results provide the framework for a nondestructive method for estimating whole-tree carbon assimilation rate and ecosystem GPP over daily-to weekly time scales.
理解植物-大气 CO2 交换的控制因素对于量化不同时空尺度的碳预算非常重要。在这项研究中，我们使用了一种简单的方法来估算亚高山森林生态系统中整棵树的 CO2 同化速率（A（Tree））。我们分析了提取针叶糖的碳同位素比值（δ13C），并将其与白天叶片-空气水汽压亏缺结合起来，估算树木水分利用效率（WUE）。然后，利用 sap flow 技术观测到的树木蒸腾速率（E）来估算 A（Tree）。将森林中三种主要树种的 A（Tree）估算值与物种分布和树木大小相结合，利用生态系统过程模型估算和总初级生产力（GPP）。敏感性分析表明，A（Tree）的估算值对 E 的动态变化比 δ13C 更为敏感。在生态系统尺度上，由于其对季节性气候变化的敏感性更大，落叶松的丰度对 GPP 的季节性动态影响远远大于云杉和冷杉。结果为一种非破坏性的方法提供了框架，用于估算整棵树的碳同化速率和生态系统的 GPP，时间尺度从每日到每周。
