01641naa a2200217 a 450000100080000000500110000800800410001910000190006024501550007926000090023452009920024365000110123565000150124665000100126165000200127165300100129165300220130165300150132370000160133877300690135412787272024-05-27       1989    bl uuuu     u00u1 u    #d1 aKUULUVANEN, T.  aSimulation of within-tree and between-tree shading of direct radiation in a forest canopybeffect of crown shape and elevation.h[electronic resource]  c1989  aThe pattern of momentary within-tree and between-tree shading of foliage in direct radiation flux was simulated in fully-stocked model stands with a Poisson distribution of trees. The canopies were composed of umbrella-like (crown height/crown radius, H:R=3), average (H:R=8) or columnar (H:R=20) tree crowns. The momentary radiation-extinction probability was calculated for a large number of points (106-107 points per hectare) within the canopy. The radiation attenuation rate depended on the projected leaf-area density within the crown. At solar elevations of 50 and 450, columnar crowns had the most between-tree and the least within-tree shading, while at a high sun elevation (850) the same was true for umbrella-like crowns. At low and medium sun elevations (50 and 450), crown shape had a small effect on the total shading of foliage. At a high sun elevation, flat, horizontally extended crowns were the best illuminated, as within-tree and between-tree shadings were both low.  acanopy  adimensions  alight  asolar radiation  aCrown  aLight penetration  aSimulation1 aPUKKALA, T.  tEcological Modelling, Amsterdamgv. 49, n. 1-2, p. 89-100, 1989.