Collaborative Research: Distribution of Photosynthetic Capacity in Conifer Canopies: The Role of Shoot Geometry, Leaf Morphology, & Nitrogen Concentration

合作研究：针叶树冠层光合能力的分布：芽几何形状、叶子形态的作用，

• 批准号: 9630866
• 负责人: Douglas Sprugel
• 金额: $ 11.47万
• 依托单位: University of Washington
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1996
• 资助国家: 美国
• 起止时间: 1996-07-15 至 2000-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9630866&HistoricalAwards=false
• 关键词: Collaborative; Research; Distribution; Photosynthetic; Capacity

9630866 Sprugel Nitrogen is one of the most important elements controlling plant growth in both natural and agricultural ecosystems. Ecophysiology theory suggests that the distribution of nitrogen within a plant canopy should match the distribution of intercepted light; that is, there should be much more nitrogen near the top of the canopy (where light levels are highest) than in the more shaded areas near the bottom of the canopy. However, when theoretical predictions have been compared with actual plant canopies, the results have been mixed at best. Nitrogen distribution in most canopies does show the same general pattern as that predicted by theory. However, the mechanism by which nitrogen content changes differs between species, and the difference in nitrogen levels from the top to the bottom of the canopy is rarely as large as the theory predicts that it should be. The investigators have developed a hypothesis that explains this variation in mechanisms and also suggests some reasons why the variation in nitrogen does not always match the pattern of light distribution, especially in older leaves. They propose to test this hypothesis in three different western conifer species: Douglas-fir (Pseudotsuga menziesii), the most important timber species in the Pacific Northwest; Pacific silver fir (Abies amabilis) an important tree of high altitude forests; and ponderosa pine (Pinus ponderosa), the dominant tree in dry forests throughout the western United States. If the hypothesis proves correct, it will provide a better understanding of the organizing principles for shoot structure and function within complex canopies, and will assist in efforts to "scale up" gas fluxes from leaves to canopies--a critical component of attempts to model and predict the consequences of climate change in western conifer forests.

9630866 Sprugel 氮是自然和农业生态系统中控制植物生长的最重要元素之一。 生态生理学理论表明，植物冠层内氮的分布应与截获的光的分布相匹配。也就是说，树冠顶部附近（光照水平最高的地方）应该比树冠底部附近阴影较多的区域有更多的氮。 然而，当将理论预测与实际植物冠层进行比较时，结果充其量是好坏参半。大多数冠层中的氮分布确实显示出与理论预测相同的一般模式。 然而，氮含量变化的机制因物种而异，冠层顶部到底部的氮水平差异很少像理论预测的那样大。 研究人员提出了一个假设，解释了这种机制的变化，并提出了氮的变化并不总是与光分布模式相匹配的一些原因，特别是在老叶中。 他们提议在三种不同的西部针叶树种中检验这一假设：花旗松（Pseudotsuga menziesii），太平洋西北地区最重要的木材树种；太平洋银杉（Abies amabilis）是高海拔森林的重要树种；黄松（Pinus ponderosa）是美国西部干燥森林中的主要树种。 如果这一假设被证明是正确的，它将有助于更好地理解复杂冠层内芽结构和功能的组织原理，并将有助于“扩大”从叶子到冠层的气体通量——这是模拟和预测西部针叶林气候变化后果的尝试的关键组成部分。