DIAMETER STRUCTURE AND ITS RELATIONSHIP WITH FRUIT AND SEED PRODUCTION IN A NATIVE BRAZIL NUT GROVE IN MATO GROSSO

The study aimed to evaluate the annual variation in fruits and seed productivity of Brazil nut trees and to determine the association between diameter structure and fruit/seed productivity in a semi-deciduous seasonal forest undergoing logging in Mato Grosso, Brazil. Data were collected in two permanent plots (300 m x 300 m) spaced 3.5 km apart. All trees ( n = 279) with diameter at breast height (DBH) ≥ 10 cm were tagged and productivity was monitored from October to February during each of the five harvest seasons between 2012 and 2017. Associations between seed dry weight (SDW) per tree and DBH, crown position, crown shape and fruit number were established using stepwise regression analysis. The model based on DBH was a good predictor of seed production and revealed that SDW tree -1 increased by 1.3 kg on average for every 10 cm increase in DBH. Trees reached the reproductive phase with DBH < 50 cm. Characteristics and mean SDW values of the diameter classes were: 10 cm ≤ DBH < 30 cm - dominated/suppressed trees/malformed crowns (0.12 kg tree -1 year -1 ); 30 cm ≤ DBH < 70 cm - dominant/co-dominant/good crown shape (1.23 kg tree -1 year -1 ); DBH ≥ 70 cm - dominant/co-dominant/well-formed crowns (4.8 kg tree -1 year -1 ). DBH explained 34% of the variation in the mean SDW. Our results are important for the sustainable management of the study stands, allowing the assessment of current and future yields of Brazil nuts for the purpose of improving the economy of forest-dependent communities and associated enterprises.