Linking forest structure to forest productivity using remote sensing

森林生产力，或森林如何生长，受到树木、树枝和树叶在树冠内的位置的影响。反过来，这种复杂性是由森林中发现的物种和单个树木的结构决定的。过去的研究报告称，树种多样性更高的森林具有更高的生产力；例如，高多样性的森林可以有更少的树木间距，导致更多的树木在一个给定的区域。然而，树木在混合林分中所占的冠层与在单一林分中所占的冠层不同。然而，多样性与结构对森林生产力的相对影响仍然难以理清。因此，问题出现了：森林管理者应该以复杂性或多样性为目标来提高林分生产力吗？遥感技术的进步，如地面和机载激光雷达，使研究人员和森林管理者能够获得对森林冠层详细结构的宝贵见解。本研究计划的总体目标是通过描述森林结构和了解其与森林生产力的关系来改善森林管理实践。为了实现这一长期目标，拟议的研究计划将分为三个主题：(1)开发易于使用的指数来量化森林管理的林分结构。这些遥感衍生的指数量化了林分内木材和叶片材料的三维排列；（二）了解森林结构如何影响森林生产力；（III）在建模框架内综合这些获得的信息，以得出新的森林管理工具。森林结构对生产力的影响将在生态生理学和生物力学框架内进行研究。生长在不同环境和结构条件下的树木生长情况不同。在生态生理学方面，气候变量被假设会影响树木内部的水流以及树木在不同隔间间的生长变化。在生物力学方面，树木受到强风的影响会有利于二次生长（例如树的底部直径的生长），以防止在机械约束下屈曲。因此，风与森林相互作用的方式与树冠结构有关，通过树冠-大气交界处的流体动力学和树冠孔隙度，风通过树冠孔隙度进入森林。研究结果将有助于更好地理解森林多样性和结构复杂性如何相互作用并影响森林生产力。为了使森林工业继续或增加其对加拿大经济的重要贡献，森林管理必须适应新的现实，例如基于生态系统的管理和全球变化。自然和人为干扰将继续增加加拿大森林的压力。对林分结构和生长有了更好的了解，就可以评估如何最好地构建森林，以确保它们能够适应预计的压力。

Forest productivity, or how forests grow, is influenced by how the trees, their branches, and their leaves are positioned within the canopy. This complexity is, in turn, determined by both the species found in the forest and the architecture of individual trees. Past studies have reported that forests with a greater diversity of tree species have higher productivity; for example, higher-diversity forests can have less-spaced trees, leading to more trees in a given area. However, trees in mixed stands will occupy the canopy differently than if found within a monospecific stand. The relative effect of diversity versus structure on forest productivity remains nevertheless difficult to untangle. The question thus arises: Should forest managers aim for complexity or diversity to increase stand productivity? Advances in remote sensing, such as terrestrial and airborne LiDAR, have enabled researchers and forest managers to gain valuable insight into the detailed structure of forest canopies. The general objective of this research program is to improve forest management practices by describing forest structure and understanding its relationship to forest productivity. To achieve this long-term goal, the proposed research program will be divided into three themes: (I) develop easy-to-use indices to quantify stand structure for forest management. These remote sensing-derived indices quantify the 3D arrangement of woody and leaf material within a stand; (II) understand how forest structure influences forest productivity; and (III) synthesize this acquired information within a modelling framework to derive new forest management tools. The effect of forest structure on productivity will be studied within both an ecophysiological and biomechanical framework. Trees growing under different environmental and structural conditions differ in their growth. In terms of ecophysiology, climatic variables are hypothesized to influence how water flows within a tree and how growth shifts among the various tree compartments. In regard to biomechanics, trees subjected to strong winds will favour secondary growth (e.g. diameter growth at the base of the tree) to prevent buckling under mechanical constraints. The way wind interacts with forests is thus linked to canopy structure, through fluid dynamics at the canopy-atmosphere junction, and canopy porousness, by which wind enters the forest. The results will help better understand how forest diversity and structural complexity interact and influence forest productivity. For the forest industry to continue or increase its critical contribution to Canada's economy, forest management must adapt to new realities, such as ecosystem-based management and global change. Natural and anthropogenic disturbances will continue to increase pressure on Canada's forests. An improved understanding of stand structure and growth permits an evaluation of how best to structure forests to ensure they are resilient to projected pressures.