The occurrence of heart splitting during the crosscutting of logs was discussed in relation to the released strain on Eucalyptus spp. logs. The strains released in the longitudinal and tangential directions were measured by the strain-gauge method and were correlated with the length of the heart split measured on the same logs. There were differences in the longitudinal strain; however, no significant correlation was found with the diameter that could be converted to a mean annual increment (i.e., a relation with the growth rate). The initial splits expand with the time after felling. The longer the initial split, the longer is the length 1 week after felling. The split length was significantly smaller at the butt end of the first log of every tree than at the other end, but there were no significant differences between the split length at the top of the first logs and at either end of the second logs, although there were differences among individual trees. The length of the heart split correlated with the released strain near the pith, which was estimated using Kubler's equation. The longitudinal released strain measured on the surface of logs is a good indicator of the heart splitting when crosscutting logs.

No abstract

Most of the wood from Eucalyptus globulus Labill. plantations in Uruguay is harvested for pulp industry at an average age of 11 years. In this study we evaluated the volume and quality of the wood produced and the economic return for owners using different rotation length (from 6 to 13 years) and two different provenances (Jeeralang, Australia and Chivilingo, Chile) in experimental plots planted at two different sites (southwest and southeast of Uruguay). Silvicultural practices, industrial process, and economic aspects of the plantations were evaluated by measuring the following variables: survival, individual and per hectare growth, basic density, cellulose yield, wood consumption, cellulose production per hectare, dry solids content, fiber length, paper resistance, internal rate of return, and soil expectation value. The results showed that an increase in the harvest age generates: (i) an increase in the production of wood and cellulose per hectare at decreasing rates; (ii) an increase in wood density and yield; (iii) a reduction in the consumption of wood and solid contents in the cooking liquor; and (iv) a reduction in economic profitability at the farm level. No differences were found in the fiber length and resistance properties of the paper from wood harvested at different ages.

Se evaluaron dos materiales genéticos de E.globulus (Jeeralang y Chivilingo) en las zonas litoral y sureste del Uruguay, cada uno con dos turnos de cosecha. En cada turno se evaluó el crecimiento, la productividad de celulosa y las propiedades de las fibras. Las edades de cosecha variaron de 6,6 años a 10,7 años y el período entre evaluaciones fue de aproximadamente dos años. En general se obtiene una mejora en las propiedades pulpables, en la eficiencia productiva de convertir madera en celulosa y de las propiedades de las fibras al aumentar la edad de cosecha.