Canopy structure: a key to forest function
The canopy is a world of surfaces that interact with the atmosphere and provide living space for organisms. How the canopy works is related to the activity, amount, and organization of this surface area. Generally, with more leaf area there is greater potential photosynthesis, reduction of wind speed, and moderation of interior climate. The details of how canopy material is organized in space are also important for prediction of forest functions like growth, microclimate, and habitat complexity. An analogy: it's not just the number of machines that determines the output of a factory, but how well they are working together.
We think of structure, "the organization of the aboveground parts of vegetation," in terms of measurable quantities. It's useful to know the total amount of canopy material, like the combined weight or area of leaves, the maximum height of the forest, or its cover (the proportion of overhead sky that is covered by leaves). But information about how the parts of the canopy are organized in space is even more helpful.
We measure canopy structure at different levels of detail. For example, we note the size, thickness, position, orientation, and chemical characteristics of individual leaves within the canopy. We measure the average vertical organization of leaf area - at what heights is the leaf area most concentrated? We study how the canopy surface varies from place to place - how rumpled is the top of the canopy and how large are the openings?
Click below for an Adobe Acrobat pdf file of an article (2 MB) that describes the connections between canopy structures and microclimate:
Parker, G.G. 1995. Structure and microclimate of forest canopies. In: M. Lowman and N. Nadkarni, eds. Forest canopies: a review of research on a biological frontier. Academic Press, San Diego, CA.