Extracción y reciclaje de elementos nutritivos por cosecha de Eucalyptus globulus en Uruguay

Abstract

SUMMARYEucalyptus commercial plantations extract high quantities of nutritious elements, although the proportion exported after harvest is relatively low. The aims of the work were: a) To quantify the concentration and distribution of nutritious elements in different components of a Eucalyptus globulus harvest b) To quantify decomposition rates of the harvest residues through the time, and the potential recycling of nutritious elements to the soil. In a 10 year-plantation on a Typic Hapludert, 24 trees with average height and DBH were harvested. The aerial biomass and total extraction of nitrogen, phosphorus, potassium, calcium and magnesium of logs, branches, bark and leaves were measured. For 24 months the decomposition of residues was measured with periodical samplings. The debarked commercial logs represented 77.5 % of the produced biomass; and the proportions of nutritious elements exported with them were 32, 45, 19, 18 and 33 % of nitrogen, phosphorus, potassium, calcium and magnesium respectively. The highest concentrations of nutritious elements were found in leaves and bark. The average residue decomposition was 30 % of the initial aerial biomass. Leaves lost the highest proportion of biomass (68 %) and nutritious elements over 24 months, whereas the bark was the most resistant to decomposition. Potassium was released from the residues faster than the others, whereas calcium showed the lowest loss. Nitrogen, phosphorus and magnesium decreases were more gradual, proportional to the decomposition rates. De-barking in the site avoids the exportation of important amounts of nutritious elements.Key words: decomposition rate, harvest residues, forest biomass. RESUMENLas plantaciones comerciales de Eucalyptus globulus extraen altas cantidades de elementos nutritivos, aunque la proporción exportada luego de la cosecha es relativamente baja. Los objetivos del trabajo fueron: a) cuantificar la concentración y distribución de elementos nutritivos en diferentes componentes de cosecha de E. globulus; b) cuantificar las tasas de descomposición de residuos de cosecha en el tiempo, y el potencial reciclaje de elementos nutritivos al suelo. En una plantación de 10 años de edad sobre un Typic Hapludert se cosecharon 24 árboles con DAP y altura promedio. Se cuantificó la biomasa aérea y la extracción total de nitrógeno, fósforo, potasio, calcio y magnesio en trozas, ramas, corteza y hojas. Durante 24 meses se midió la descomposición de restos mediante muestreos periódicos. Las trozas descortezadas representaron 77,5 % de la biomasa aérea, y las proporciones de elementos nutritivos exportadas con ellas fueron 32, 45, 19, 18 y 33 % de nitrógeno, fósforo, potasio, calcio y magnesio, respectivamente. Las mayores concentraciones de elementos nutritivos se encontraron en corteza y hojas. La descomposición promedio de los restos fue 30 % de la biomasa aérea inicial. Las hojas perdieron la mayor proporción de biomasa (68 %) y elementos nutritivos al término de 24 meses, mientras que la corteza fue más resistente a la descomposici...

Decomposition of <i>Eucalyptus sp.</i> and <i>Pinus taeda</i> Harvest Residues under Controlled Temperature and Moisture Conditions

“…A field study conducted in a E. globulus Labill plantation in Uruguay showed leaves to be the most rapidly decomposing component, with biomass loss amounting to 70% after two years, while twigs (small and medium-sized) and bark had lower decomposition rates of 29% and 19% respectively (González et al, 2016). Also for E. grandis Hill ex Maiden and E. dunnii Maiden, the rapid decomposition of leaves (50% biomass loss after two years) was followed by that of twigs smaller than 1 cm in diameter (Hernández et al, 2009).…”