How long does the Amazon rainforest take to grow commercially sized trees? An estimation methodology for Manilkara elata (Allemão ex Miq.) Monach

• Published in: Forest ecology and management 2020-10, Vol.473, p.118333, Article 118333
• Main Authors: Ferreira, Thamires Mendes Coelho, de Carvalho, João Olegário Pereira, Emmert, Fabiano, Ruschel, Ademir Roberto, Nascimento, Rodrigo Geroni Mendes
• Format: Article
• Language: English
• Subjects: Forest growth and yield; Forest management; Tropical rainforest; Weibull function
• ISSN: 0378-1127; 1872-7042
• DOI: 10.1016/j.foreco.2020.118333

•The proposed models provided reliable estimates of the M. elata diameter growth.•The models provided solid estimates of the average growth time of M. elata trees.•M. elata trees with DBH = 5 cm needed almost a millennium to reach commercial size.•Our results agreed with earlier studies that guided Forest Management laws in Brazil.•The method used to predict DBH growth period is option for forest planning purposes. It is important to know the growth rate of the species to be managed to establish sustainable forest management plans because from this information, it is possible to know which species have reached the minimum commercial size to be collected in future harvests. Manilkara elata (Allemão ex Miq.) Monach is considered one of the most commercialized timber tree species, both inside and outside of Brazil. Thus, the objective of this study was to model the growth rate and the time required for the trees of this species to reach the minimum cutting diameter defined by the current Brazilian legislation; the analysis was based on the adapted Weibull function with data from 31 years of monitoring in the National Forest of Brazil in Tapajós, Pará, Amazon, Brazil. Three models were proposed to estimate (i) the annual periodic increase in diameter (API), (ii) the future diameter (df) and (iii) the time period in years (t) that each tree would need to reach a future diameter according to the average growth rate of the target species and its forest community. Taken together, the data from the managed and unmanaged areas showed no statistically significant differences between the values observed and estimated by the proposed model when assessed with the Graybill F test. The adapted Weibull model performed well when estimating the annual periodic increment and future tree diameter of the M. elata population. Based on the diameter growth rate, the 5 cm diameter M. elata trees would require 601–781 years to reach the minimum commercial diameter of 50 cm, but the 40–49.9 cm diameter trees that are considered stock for the next harvest would take an average of 20 years to reach this commercial diameter. As the estimated average growth time is shorter than the cutting cycle prescribed by the legislation (25–35 years), it is recommended that forestry treatments that favor longer survival of M. elata individuals be adopted to achieve greater continuous production by primarily considering the long period that young individuals need to reach the cutting diameter.