EFFICIENCY OF SAMPLING DESIGNS FOR EVALUATING THE DENSITY OF NATURALLY REGENERATED CONIFEROUS STANDS

Abstract

Size, number, and spatial distribution of sampling sites are of fundamental importance to evaluate the density of naturally regenerated stands. The objective of this study was to compare the efficiency of different sampling designs to evaluate the density of naturally regenerated coniferous stands in Durango, subjected to regeneration cuts between 1989 and 1990. Twenty 1.0 ha plots were isolated from a similar number of developed forest stands. Each plot was divided into subplots of 5 x 5 m each, in which the number of seedlings was measured. This sampling scheme allowed the testing of different sizes of sampling plots. The number of sampling units was estimated at the probabilities (1-?) of 90 and 95 %, and six different spatial distributions of sampling units were tested, including four systematic and two randomly established. Sampling units with smallest size (5 x 5 m) were most efficient in quantifying density of natural regeneration. It was estimated that 28 sampling plots of 5 x 5 m distributed randomly or systematically (with two diagonal transects and two center-crossed transects) provide precise predictions of natural regeneration.