Woody-to-total area ratio determination with a multispectral canopy imager

Summary Leaf area index (LAI) – defined as one half of the total green leaf area per unit ground surface area – can be determined by direct or indirect methods. Three major sources of errors exist in indirect LAI measure-ments: within-shoot clumping, beyond-shoot clumping and non-photosynthetic components. The effect of non-photosynthetic components on LAI measurements can be described by the woody-to-total area ratio, a; however, no convenient and efficient indirect methods have been developed to estimate a, especially the variations in a with zenith angle h, a(h). We describe the development and use of a multispectral canopy imager (MCI) to estimate a and a(h) by considering the effects of non-random distribu-tions of canopy elements and woody components and the overestimation of needle-to-shoot area ratio on wood