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This study presents a yield model for aboveground biomass production from three species the Eucalyptus in northern and western regions of Uruguay, based on sampling records from intensive crop plantations. High-density eucalyptus plantations represent a forestry alternative for the production of forest biomass. This work assessed the survival and growth of three eucalyptus species (Eucalyptus benthamii Maiden & Cambage, E. dunnii Maiden and E. grandis Hill ex Maiden) planted at densities of 2220, 3330, 4440 and 6660 trees ha−1, for a period of 57 months in northern (Tacuarembó) and western (Paysandú) regions of Uruguay. Linear and logarithmic equations of individual volume were fitted by site and species. The survival of E. grandis, E. benthamii and E. dunnii was not related to planting density, and the highest mortality values occurred in Tacuarembó. The effects of competition among trees were more evident at the highest planting density for E. grandis. In all species, the reduction in diameter was more marked than that of height, as planting density increased. Tree volume showed the same trend, and this was higher with higher planting densities. At Tacuarembó, the volume was the highest with E. benthamii at 6660 trees ha−1 (416.4 m3 ha−1), and, at Paysandú, the highest production was obtained with E. grandis (370.7 m3 ha−1) and with the densities of 4440 and 6660 trees ha−1 (305.9 and 315.3 m3 ha−1, respectively). With all species and planting densities, there was an increase in the accumulated volume during the 57-month study period; however, growth curves indicate that the maximum production per unit time and, therefore, the optimum harvest time occurred at 48 months. In this work, it has been shown that the use of intensive short-rotation plantations of eucalyptus for the production of biomass in Uruguay is suitable in soils prioritized for forestry.

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Analytical pyrolysis (Py-GC/MS) at 500 ºC was applied to study wood composition of Eucalyptus species (E. grandis, E. dunnii and E. benthamii) which are relevant for pulping in Uruguay. Multivariate data treatments mainly principal component analysis and discriminant analysis with automatic backwards variable selection were used to explore differences between the original wood cultivars. Multivariate analyses with automatic backwards variable selection indicated that simplified methoxyphenol patterns (up to 10 compounds) are sufficient for wood discrimination in terms of species and geographical origin but also with purposes of forecasting the ease of delignification of the resulting pulps measured as active alkali. No additional chemotaxonomical accuracy was achieved when the data sets were enlarged with carbohydrate-derived products. On the other side, discriminant or forecasting models were much less significant when based on individual diagnostic compounds, groups of compounds, or the classical syringyl-to-guaiacyl (SG) ratio. Principal component analysis indicated that the variability in lignin composition due to bioclimatic variations (spatial replications) was more significant than that due to phylogenetic differences (species and cultivars).

Se compararon diferentes ecuaciones de volumen y ahusamiento, evaluando en especial el uso de ecuaciones compatibles, con el objetivo de ser utilizadas en inventarios forestales o sistemas de apoyo a la toma de decisiones. Utilizamos datos de 863 y 932 árboles correspondientes a las especies Pinus taeda y Eucalyptus grandis respectivamente, provenientes de plantaciones situadas en los departamentos de Rivera, Tacuarembó, Paysandú y Río Negro en Uruguay. En general, los rankings de ecuaciones fueron consistentes para ambas especies; para la estimación de volúmenes las ecuaciones con mayor ajuste fueron aquellas presentadas por Clutter et al. (1983) y Schumacher y Hall (1933) para P. taeda y E. grandis respectivamente, mientras que para la descripción de perfiles el modelo que mejor se ajustó fue la ecuación de exponente variable presentada por Muhairwe (1999) y modificada por Methol (2001). La mejor ecuación de ahusamiento tipo compatible rankeó en posiciones intermedias para ambas especies, representando igualmente una opción satisfactoria para aquellos productores forestales que deseen usufructuar las ventajas de este tipo de ecuaciones.

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