Linking forest structure to forest productivity using remote sensing

点击翻译按钮获取中文摘要

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.