Abstract
Intensive management of forest stands can increase biomass production, as well as increase the removal of nutrients from the site. This study therefore sought to simulate different harvest intensities and to calculate the nutrient-use efficiency of Eucalyptus urograndis in different types of soil. The study was carried out in a plantation of seven-year-old hybrid E. urograndis in the city of Telêmaco Borba, Paraná, Brazil. The study site included two sub areas with sandy soil and clayey soil (Cambisols Inceptisol and Ferralsols Oxisols, respectively). Using biomass and nutrients stock data, nutrient removal was simulated under five different harvest scenarios. Nutrient-use efficiency was obtained from the relation between the amount of biomass and nutrients of each tree component. Harvesting the whole tree resulted in the removal of approximately 61% of the nutrients from the site in sandy soil, while in clayey soil 57% of the nutrients were removed. With harvesting of only the commercial stemwood, only 22% of the nutrients were removed from the sandy soil, and 21% from the clayey soil. Stemwood was the component that had the highest nutrient-use efficiency values for all the analyzed nutrients. In conclusion, to achieve nutritional sustainability of E. urograndis stands, the best harvesting system involves the removal of only commercial stemwood. For the production of stemwood, sandy soils have a greater biological efficiency of calcium and magnesium when compared to clayey soil.
Highlights
Use of renewable energy was boosted by the oil crisis in the 1970s, increasing the demand for energy biomass, which led to the search for available waste after forest harvesting operations (Egnell, 2017)
Harvesting tree tops in sandy soils can significantly increase nutrient exports when compared to harvesting this component in clayey soils
The results of the present study indicate that harvest intensity planning should be adopted locally, and should be based on the nutrient removal of each tree section harvested and the type of soil, as the clayey soil was suitable for a higher number of rotations of seven-year-old E. urograndis, in commercial harvesting systems of the stemwood
Summary
Use of renewable energy was boosted by the oil crisis in the 1970s, increasing the demand for energy biomass, which led to the search for available waste after forest harvesting operations (Egnell, 2017). Intensively managed forest stands can increase biomass production, but may increase the removal of nutrients from the site (Viera et al, 2011). Viera et al, (2013) emphasize that intensively managed plantations with the use of short rotations, without predicting a minimum period required for nutrient replacement, have been found to be the main reason for the chemical exhaustion of soils. For long-term forest management, knowledge of the relationships between the amount of nutrients removed by harvests and the bioavailability of nutrients at the site is imperative in order to achieve sustainable energy standards under various rotations (Santana et al, 2008). There are differences between plantations and natural ecosystems, which are self-sustainable. Forest plantations are a diversified form of land use, and in order to develop plantations that do not have significant negative impacts on the ecosystem, plantations need to be in harmony with the ecological properties of their environment
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