STATISTICAL DESCRIPTION OF THE ARCHITECTURE OF A FAST-GROWING WILLOW COPPICE

The investigation of the PAR variability in a willow forest requires a detailed description of architecture at the leaf, branch, stem and ca nopy levels. Due to the great variability of the object under study, p arameters of the architecture should be considered as stochastic quant ities and expressed by their probability density functions (PDF). Esta blishment of correlations between different architectural parameters e nables a reduction in the great number of phytometrical measurements. A statistical phytometrical methodology, describing plantation archite cture during the first three growing gears, has been elaborated and ap plied for a willow (Salix viminalis) coppice. The whole canopy was div ided into three layers. The upper foliage layer consists of foliage cy linders (current year shoots and branches with leaves) with given geom etrical characteristics. The lower foliage layer consists of previous year stems and branches as well as current year shoots and can be mode lled as horizontally homogeneous turbid plate medium. The lower leafle ss layer consists of nearly vertical stems only. The dynamics and deve lopment of these layers was analyzed during the years 1994-1996. The v ertical distribution of leaf area density for the whole canopy is not uniform; but can be approximated by a normal distribution. At the rela tive coppice height 0.6-0.7 leaf area density reaches its maximum valu e of 23 m(2) leaf area per m(3) canopy volume. In the years 1994, 1995 and 1996 at the end of July the leaf area index reached maximum value s 1.2, 2.6 and 4.2, respectively. The leaf inclination angle distribut ion is not uniform, the maximum being located between 20 and 40 degree s. (C) 1998 Elsevier Science B.V. All rights reserved.