Efeitos de tratamentos silviculturais no crescimento de Platonia insignis Mart. Clusiaceae (bacurizeiro) em floresta secundária no nordeste paraense, Brasil.

Abstract

The bacurizeiro, Platonia insignis Aubl., is a fruit-producing species of considerable economic importance in the Brazilian state of Pará. The species is abundant in the secondary forests of the northeastern extreme of the state. The diametric growth of the species was evaluated in two secondary forests following the application of different forestry management procedures applied for the improvement of fruit production. The present study evaluated the effects of forestry management techniques on the mortality, treefall, crown shape and illumination, and trunk integrity (presence of liana and termites).The experiment was established in 2005 in five rural communities in the municipality of Bragança, Pará. The experimental design was based on a factorial approach in randomly located blocks of forest, with four replicates in young (SF1) and intermediate (SF2) successional forest, with plots of 10 m x 40 m (400 m²) and 20 m x 40 m (800 m²), respectively. Treatments were divided into two factors. Factor A (silvicultural treatment), which has three classes: a1 = control; a2 = moderate thinning, and a3 = extreme thinning. Factor B (time treatment), which is based on five distinct time periods: b1 = October, 2005, to September, 2007 (1.917 years), b2 = September, 2007, to November, 2009 (2.167 years), b3 = November, 2009, to December, 2010 (1.083 years), b4 = December, 2010, to December, 2011 (1 year), and b5 = October, 2005, to December, 2011 (7.167 years). This design resulted in a total of 15 factorial treatments for the APId (Annual Periodic Increase in diameter). For the analysis of mortality, treefall, crown shape and illumination, and trunk integrity, only the data from the period between 2009 and 2011 were analyzed, providing a total of nine factorial treatments. The statistical analysis was based on an Analysis of Variance (ANOVA) and the SNK test, with a significance level of α = 0.05, run in the SAEG program. In SF1, the APId was significantly higher in a3 (0.71 cm/year) in comparison with a2 (0.56 cm/year) and a1 (0.41 cm/year). In relation to the factor time, the APId values were significantly different between the 1.917 year (0.74 cm/year), 2.16 year (0.61 cm/year), 1.083 year (0.37 cm/year), and 1 year periods (0.40 cm/year). Mortality was significantly higher in a1 (1.40 %) in comparison with a2 (0%) and a3 (0.16%). The proportion of full, regular crowns decreased over time, with a significant reduction in 2011 (57.6%) in comparison with 2009 (78.6%) and 2010 (88.1%). Totally open crowns (high illumination) decreased over time, with rates in the a2 (52%) and a3 plots (49%) being significantly different from those in the a1 plot (21.7%). The presence of lianas was similar in the a2 (20.8%) and a3 plots (19.8%), but both were significantly different in comparison with a1 (47%). The presence of termites increased over time, and was significantly higher in 2011 in comparison with 2009, reaching a maximum value in a3 (12.7%), which was significantly higher than the values recorded in a2 (2.8%) and a1 (1.7%). In SF2, the APId was significantly higher in plot a3 (0.66 cm/year), followed by a2 (0.40 cm/year), and a1 (0.27 cm/year). The AIPd varied significantly in all periods in comparison with 1.083 years (0.30 cm/year). There were also significant differences in a3 compared with other treatments and time periods, with the exception of 1.083 years. The presence of full, regularly-shaped crowns also decreased over time, with a significant difference in 2011 (49.4%), while there was no statistical difference between the a2 (72.0%) and a3 plots (73.1%). Totally open crowns also declined over time, significantly in 2011 (21.7%), with significant differences also being recorded between plot a1 (37.7%) and a2 (55.3%) and a3 (59.5%). The presence of lianas increased significantly over time, with the smallest rate of increase being recorded in a3 (4.8%). The presence of termites also varied over time, and was significantly different in a3 (21.8%) in comparison with a2 (10.4%) and a1 (3.2%). The silvicultural management procedures (plots a2 and a3) favored the growth of P. insignis. The variables that were affected by moderate and extreme thinning in SF1 were mortality, crown illumination, and trunk integrity (termites and lianas), whereas in SF2, the variables affected were the shape and illumination of the crown and trunk integrity. It is important to note that neither of the silviculture procedures had any effect on treefall rates in either of the secondary forest habitats studied.