THINNING INTENSITY EFFECTS ON DIAMETER GROWTH DYNAMICS OF AFRICAN MAHOGANY STANDS

Abstract

Background: African mahogany (Khaya spp.) is a valuable timber species that has gained increasing attention in Brazil due to its silvicultural advantages over Swietenia macrophylla, particularly its superior growth performance and resistance to native pests. Thinning is a key silvicultural practice, yet optimal timing and intensity remain unclear for African mahogany, as most commercial timber has historically been sourced from native forests. This study evaluated the effects of different thinning intensities on diameter growth over four years in two African mahogany stands in Brazil (established in 2013 and 2014) with an initial density of 333 trees ha⁻¹. 

Results: In 2020, a randomized complete block design with three replications was implemented, applying light (308 trees ha⁻¹), moderate (258 trees ha⁻¹), and heavy (206 trees ha⁻¹) thinning treatments. The statistical analysis was restructured using a factorial arrangement. Results indicated a significant effect of stand age (p < 0.05), whereas thinning intensity and the interaction between factors were not significant (p > 0.05). Complementary analyses using aligned rank transform (ANOVA -ART) were conducted to assess temporal variation within each stand, indicating increased diameter growth over time. Linear regressions showed DBH growth across treatments, and diameter distributions, modeled using the Weibull 3P function, shifted toward larger classes, particularly under moderate and heavy thinning. 

Conclusion: Stand age was the main factor influencing diameter growth, while thinning intensity showed no significant overall effect under the factorial approach. However, temporal analyses suggest that density reduction contributes to shifts toward larger diameter classes, supporting thinning as a relevant management practice in African mahogany plantations.