Comparative Analysis of Sampling Systems in Thinned Pinus taeda L. Plantations

The objective of this study was to compare the sampling methods of fixed area, Bitterlich, Strand, and Prodan distributed through random and systematic processes in a 6.3 hectare Pinus taeda L. plantation located in the municipality of Lages, in the state of Santa Catarina, subjected to selective and systematic thinning. A 100% inventory (forest census) was carried out, measuring the diameters at 1.3 meters above ground level (d) of all trees in the stand. Additionally, sampling systems (method + process) were designed to estimate the main population parameters (basal area - G, volume - V, and number of trees - N) per hectare. In the random process, the central coordinates (latitude and longitude) of the sample units were selected by random draw, while for the systematic process, only the central coordinate of the first unit was drawn, and the others were distributed at 100 meter intervals. Sampling errors were calculated, and an analysis of variance was performed for the variables G (m2·ha-1), V (m3·ha−1), and N (trees·ha−1) using a factorial arrangement design, considering the factors: sampling processes (systematic and random) and sampling methods (rectangular fixed area, circular fixed area, Bitterlich, Strand, and Prodan). The results of this study demonstrated that the interaction between the different sampling methods and the random and systematic processes did not result in significant differences. Significant differences were observed only in the volume (V) estimates generated by the random and systematic processes, with the estimates from the random process being closer to the parametric value.