01427naa a2200217 a 450000100080000000500110000800800410001910000160006024501090007626000090018552008070019465000130100165000160101465000260103065000170105665300150107365300230108870000170111170000170112877300640114510553721999-06-02       1991    bl ---       0--  u    #d1 aCHEN, J. M.  aEvaluation of hemispherical photography for determining plant area index and geometry of a forest stand.  c1991  aHemispherical photographs were taken beneath an 80-years-old Douglas-fir (Pseudotsuga menziesii) forest stand under clear and overcast sky conditions, and under clear sky with the canopy partially corered 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 technique. Photographic exposure was determined by matching the Le values obtained from the photographs with those measured using the Plant Canopy Analyzer (PCA). Agreement between the inverted and measured values was found when the photographs were underexposed by 4-5 stops compared with readings of a light meter facing vertically upward under the canopy.  ageometry  aphotography  aPseudotsuga menziesii  aÁrea Foliar  aArea plant  aMetodo fotografico1 aBLACK, T. A.1 aADAMS, R. S.  tAgricultural and Forest Meteorologygv.56, p.129-143, 1991.