Evaluation of hemispherical photography for determining plant area index and geometry of a forest stand

Hemispherical photographs were taken beneath an 80-years-old Douglas-fir (Pseudotsuga menzie sii) forest stand under clear and overeast sky conditions, and under clear sky with the canopy partially covered with snow. The photographs were digitized using an optical scanner. The ‘effective plant area index’ (Le) and the distribution of the inclination angle of plant elements were obtained with Norman and Campbell's linear least-square inversion …