MICRONUTRIENTS AND BIOMASS IN Eucalyptus dunnii Maiden STAND

摘要

The expansion of silviculture in Brazil, and the consequent intensive practices for soil preparation with high demand for fertilizers require sustainable nutrient management of forest sites. The objective of this study was to quantify the biomass and the micronutrient stocks of a 60-month-old Eucalyptus dunnii stand established in Alegrete, Rio Grande do Sul. The stand was established in a Rhodic Paleudult soil with low fertility and texture varying between sandy loam and sandy-clay loam. For the sampling of stand biomass, twelve trees were harvested, sectioned at ground level, and subsequently fractionated into the components roots, leaves, branches, stembark and stemwood to determine the dry mass and micronutrient content. The total biomass of the stand was 67.49 Mg ha -1 , with mass allocation in descending order from: stem wood > root > bark > branches > leaves. Total micronutrient stocks for boron (B), copper (Cu), iron (Fe), manganese (Mn) and zinc (Zn) were 562.57, 401.46, 9913.28, 31877.82, and 766.96 g ha -1 , respectively. In addition, we found greater accumulation of Zn in the wood, high Mn accumulation especially in the bark, and high Fe content in the roots. Therefore, based on these micronutrient levels and their allocation between biomass fractions, we emphasize that the practice of retaining forest residues on-site after harvest is essential for forest nutrition through nutrient cycling and for soil conservation and fertility.