2.1. SAMPLING DESIGN
Several sampling designs are possible, depending on the aims of the study, on its
geographical scale, on the characteristics of the survey area, and on the available
resources. As a general rule, any element of subjectivity must be avoided in the
selection of sample trees and of monitoring sites (hereafter referred to as “sampling
units”). A survey of the effects of environmental alteration calls for an even distribution
of sampling units, which can be best obtained by locating them according to a
geographical grid (see chapter 9, this volume). The following procedure is suggested: