Supervivencia y características de rebrotes en tocones de dos años de cultivos dendroenergéticos / Survival rates and characteristics of spreads in two years stumps of crops with dendroenergy potential

Resumen Varias especies de los géneros Eucalyptus y Acacia son adecuadas para la producción de biomasa útil en la generación de energía. El objetivo del presente estudio fue evaluar la supervivencia y características del rebrote en tocones de cuatro especies dendroenergéticas en tres diferentes densidades poblacionales. Se utilizó un diseño de bloques completos al azar con tres repeticiones, en tres sitios (Parcelas Collipulli, La Aguada y Pilpilco Abajo) con características edafoclimáticas contrastantes. Se estudió Eucalyptus globulus, Eucalyptus denticulata, Eucalyptus nitens y Acacia dealbata en tres densidades de plantación (5 000 árboles/ ha; 10 000 árboles/ha y 15 000 árboles/ha). Se evaluó el porcentaje de supervivencia y las características del rebrote por tocón. Las variables especie, densidad de plantación y sitio de siembra afectaron los parámetros analizados. La densidad de plantación afectó el diámetro y altura de los rebrotes dominantes de tipo proventicio en las cuatro especies estudiadas. La mayor tasa de supervivencia de tocones (97 %), la presentó Eucalyptus nitens en Pipilco Abajo, con 79 % de supervivencia de rebrotes a una densidad de 5 000 árboles/ha. Sin embargo, en densidades de 15 000 árboles/ha, la supervivencia de rebrote fue de 29 %. Acacia dealbata es una especie reconocida por su capacidad de colonización, sin embargo, en La Aguada, con densidades de siembra de 5 000 árboles/ha y 10 000 árboles/ha, mostró baja tasa de supervivencia de tocones (19 % y 18 %, respectivamente) y de rebrotes (57 % y 63 %, respectivamente). La especie Eucalyptus globulus mostró altas tasas de supervivencia de tocones y rebrotes en todos los sitios evaluados, por lo que puede ser considerada como una buena opción para optimizar el sistema de monte bajo.

Abstract Several species of the genera Eucalyptus and Acacia are suitable for biomass production useful in energy generation. The objective of this research was to evaluate the survival and chaof four dendroenergetic species in three population densities. A randomized block design with three replications was used in three sites (Collipulli, La Aguada and Pilpilco Abajo plots) with contrasting edaphoclimatic characteristics. Eucalyptus globulus, Eucalyptus denticulata, Eucalyptus nitens and Acacia dealbata were studied in three plantation densities (5 000 trees/ha, 10 000 trees/ha and 15 000 trees/ha). The survival percentage and characteristics of stump regrowth characteristics of each stump were evaluated. The variables specie, plantation density and planting site affected the analyzed parameters. Plantation density affected the diameter and height of prevalent sprouts of proventic proventitious shoots in all species. Hihest stump survival rate (97 %) was presented by Eucalyptus nitens in Pipilco Abajo, with 79 % shoots survival of sprouts at a density of 5 000 trees/ha. However, at densities of 15 000 trees/ ha, regrowth survival was 29%. The Acacia dealbata is a species characterized by its colonization capacity. However, at La Aguada, which had population densities of 5 000 trees/ha and 10 000 trees/ha, it showed a low stump (19% and 18 % respectively) and shoots (57 % and 63 % respectively) survival rate. The species Eucalyptus globulus showed high stump and shoot survival rates in all sites evaluated, therefore it can be considered a good option to optimize the scrub system.

Biomass estimation equations for mesquite trees in the Americas.

Mesquite trees are the preferred dendroenergy sources in arid and semi-arid forests. In spite of their relative importance, regional aboveground biomass (AGB) equations for mesquite trees are scarce in the scientific literature. For that reason, the aims of this study were to: (a) harvest trees and develop regional biomass equations; (b) contrast measured data with equations developed previously; and (c) test the applicability of the fitted equation for mesquite trees in the arid and semi-arid forests of the Americas. We harvested 206 new mesquite trees from arid and semi-arid forests in northern Mexico (Coahuila, Nuevo Leon, and Tamaulipas) in addition to using two other previously compiled data sets from Mexico (N = 304) to develop a regional equation. To test the validity of this equation, for biomass equations reported for the rest of the country, as well as for North and South American mesquite trees, we contrasted AGB measurements with predictions of fitted equations. Statistical analysis revealed the need for a single, regional, semi-empirical equation as together the three data sets represented the variability of the aboveground biomass of mesquite trees across northern Mexico, as well as mesquite trees in America's arid and semiarid regions. Due to the large quantity of mesquite trees harvested for sampling and their variability, the regional biomass equation developed encompasses all other North and South American equations, and is representative of mesquite trees throughout the arid and semi-arid forests of the Americas.