CRESCIMENTO E PRODUTIVIDADE DE UM CLONE HÍBRIDO DE Eucalyptus urophylla X Eucalyptus grandis EM SEGUNDA ROTAÇÃO EM MACAÍBA-RN

Abstract

Studies evaluating the performance of Eucalyptus clones under different environmental conditions are essential to support silvicultural planning and the sustainable management of the species. Thus, this study aimed to assess the growth and estimate the productivity of a hybrid clone of Eucalyptus urophylla × Eucalyptus grandis in second rotation, at 36 months of age, established in Macaíba, Rio Grande do Norte, Brazil. Data collection included the measurement of circumference at breast height (CBH), taken at 1.30 m above ground level, and total tree height within two permanent plots measuring 18 m × 18 m (36 trees). CBH values were then converted to DBH (diameter at breast height). Stand volume per hectare was estimated using a mean form factor of 0.5. The results were compared with those from the first rotation. Soil samples were also collected for analysis and comparison between rotations. It was observed that mean DBH (7.09 cm) and tree height (7.91 m) were lower than those recorded in the first rotation. Consequently, stand volume (18.85 m³/hectare) and mean annual increment (MAI) (6.28 m³/hectare/year) were also significantly lower than in the first cycle. Soil analysis results revealed a significant decline in edaphic conditions between rotations. Thus, the absence of proper soil nutrient management largely explains the low productivity observed in the second rotation. Furthermore, the advanced age at harvest of the first rotation (10 years) may have contributed to the reduced productivity of the regrowth. Therefore, in coppice systems, careful technical planning is necessary to ensure the silvicultural viability of sprout management.