Evaluation of the structure of a forest subjected to different girdling intensities 28 years after intervention

Abstract

In the Brazilian Amazon Area there is no long-term research reporting on the forest structural response to thinning by girdling. This study was conducted in the Tropical Forestry Experimental Station of the National Institute of Amazonian Research. The objective was to evaluate the structure of an upland forest which had a reduction of basal area by annealing by different intensities. The study was conducted 28 years after the girdling intervention. The experiment was installed in 1985 on 15 hectares. The statistical design was randomized blocks with three replications and four treatments (T1, T2, T3 and T4) and one control (T0). As for the number of trees per hectare (trees.ha-1), the ringed area showed a high capacity for resilience, even when subjected to high levels of intervention. In treatments T1, T2 and T3 the annealing benefited both commercial and non-commercial species. In T4, there was a reversal of this trend, an increase in the proportion of commercial species was detected when compared with T0. The diameter distribution of T1 (χ2 = 16.1) and T2 treatments (χ2 = 15.4) were statistically equal to T0 and the treatments T3 (χ2 = 29.9) and T4 (χ2 = 55.3) were different. The results suggest that the forest structure still has signs of the different interventions. The silvicultural treatment used in T4 has great potential to increase the forest dynamics and tree growth without compromising the forest structure and ecological processes.