Allometry, Growth and Survival of Three Eucalyptus Species (Eucalyptus benthamii Maiden and Cambage, E-dunnii Maiden and E-grandis Hill ex Maiden) in High-Density Plantations in Uruguay

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 (Tacuarembo) and western (Paysandu) 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 Tacuarembo. 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 Tacuarembo, the volume was the highest with E. benthamii at 6660 trees ha(-1) (416.4 m(3) ha(-1)), and, at Paysandu, the highest production was obtained with E. grandis (370.7 m(3) ha(-1)) and with the densities of 4440 and 6660 trees ha(-1) (305.9 and 315.3 m(3) 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.