Modeling the light interception and carbon gain of individual fluttering aspen (Populus tremuloides Michx) leaves

Abstract

Poplars (Populus spp.) have a particular petiole morphology that enhances leaf flutter even in light winds. Previous studies have shown that this trait enhances whole canopy carbon gain through changes in the temporal dynamics and spatial distribution of light in the lower canopy. However, less is known about the effects of flutter for leaves at the top of the canopy ("sun leaves"). A computer simulation model was developed that uses latitude, time of day, day of year, azimuth and a slope component, which was varied at a 3 Hz frequency over an arc of rotation to create the flutter motion, and generate data on light interception for both surfaces of a fixed or fluttering leaf. The light files generated (10 Hz) were input into a dynamic model of photosynthesis to estimate the carbon gain for both fluttering and fixed leaves. As compared to leaves fixed at various angles and azimuths, fluttering leaves had a more uniform light interception. Depending on their angle and azimuth, fixed leaves may not always be intercepting high photon flux density (PFD) even when exposed to full sun. Leaf flutter continuously randomizes leaf angles creating uniform PFD inputs for photosynthetic reactions regardless of variation in leaf orientation and solar position. These effects on light interception could have positive impacts on carbon gain for leaves at the top of the canopy.