Etude comparative de diverses unités d'échantillonnage en futaies feuillues de hêtres (Fagus sylvatica L.). Document 86.1

This study is dealing with the choice of the size and the type of sampling units to be used in inventories of beech stands (Fagus sylvatica L.), located in the Southern part of Belgium. In most cases the stands are evenaged or unevenaged according to the places. We have considered 3 types of units : fixed circular plots (5 to 20 ares), circular plots including a fixed number of trees (6 to 15 trees) and circular plots including a minimum number of trees (from 15 to 20). From efficiency point of view, we conclude that dominant girth and top height estimations are the best ones when measuring the 2 biggest trees in a circular plot area of 5 ares, while mean girth and mean volume estimations are worth considering when based upon the ten nearest trees from the point sample. The concept of the minimum number of trees is valuable in case of estimating number of trees, basal area and volume per hectare.