Compilation of a yield table for the Douglas fir (Pseudotsuga menziesii (Mirb.) Franco) in Belgium
1992
Rondeux, J. (Faculte des Sciences Agronomiques de Gembloux (Belgium). Unite de Gestion et Economie Forestieres) | Laurent, C. | Thibaut, A.
A yield table was compiled for even-aged pure stands of Douglas fir (Pseudotsuga menziesii (Mirb.) Franco) in Belgium. It reflects the probable development of normal fully stocked stands under the silviculture at the time of the data collection. The data were collected from 256 temporary sample plots, 87 of which were remeasured 2 or 3 times. A family of functions (the Johnson-Schumacher model) was used to develop a site classification system based on the top height at age 50. The standing crop characteristics (number of trees, volume, basal area, mean stem basal area), calculated as a function of age and site index, are derived from stem girth distribution fitted by means of the Weibull function. Concerning the increments and the thinnings, the corresponding values were calculated from individual tree girth increments (from borings) and from comparison between stem distributions at the beginning and at the end of a period corresponding to a thinning cycle. The table is the basis on which a set of variable density yield tables will be prepared. The yield of Douglas fir trees in Belgium is also compared with the yield observed in neighbouring European countries.
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