Abstract
ABSTRACT 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.
Highlights
Forest stand establishment in Brazil, mainly that of eucalyptus species, has been occurring since the beginning of the last century, resulting in approximately 51 million hectares of total forests, of which seven million hectares are occupied with planted forest stands (ABRAF, 2013)
We found greater accumulation of Zn in the wood, high Mn accumulation especially in the bark, and high Fe content in the roots. 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
With respect to the micronutrient stocks in the stand, significant differences (P d” 0.05) in the concentrations of the elements were found among the different tree components (Table 2), with the micronutrients B and Cu being predominant in the leaves
Summary
Forest stand establishment in Brazil, mainly that of eucalyptus species, has been occurring since the beginning of the last century, resulting in approximately 51 million hectares of total forests, of which seven million hectares are occupied with planted forest stands (ABRAF, 2013). Along with this promising scenario, there is a concern with sustainability, and the production must be achieved and avoiding to the maximum nutritional exhaustion of the site, reducing fertilization expenditure. The aim of present study was to evaluate the micronutrient stocks of the above- and below-ground biomass of a Eucalyptus dunnii stand in the Pampa biome, Rio Grande do Sul state
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