Growing up at Different Altitudes: Changes in Energy Content of the Abies religiosa Wood

Wood is considered an important renewable energy resource with a variable elemental chemical composition, which may change according to environmental conditions (e.g., temperature, precipitation, altitude). In this study, we evaluated how heating value (HV), elemental chemical composition, and main thermoenergetic parameters of Abies religiosa wood change along an altitudinal gradient. To evaluate these parameters, wood samples were collected from six independent trees in an altitudinal gradient (3000-3500 masl) every 100 m of altitude (36 trees) and their respective HV (higher and low), thermogravimetric and immediate analysis, specific carbon energy (SCE), and fuel value index (FVI) were determined. We found that the higher and lower heating values, elemental chemical composition and the majority of the studied parameters were significantly different (p < 0.05) between altitudes. Our results suggest that A. religiosa wood from 3300 masl has more energy content than wood from 3200 and 3500 masl. Additionally, FVI showed that wood from 3500 masl is the best feedstock in order to use as a solid biofuel. Finally, the results suggest that the altitude at which A. religiosa is grown significantly affects the energetic content of their wood and throughput as a solid biofue

Desarrollo y evaluación de un método racional y no destructivo para la toma de muestras de maderas blandas utilizadas en análisis químicos

ABSTRACT Wood has been a natural resource widely used by mankind. Particularly, conifer wood is important because of its ecology, economy and geographic distribution in comparison with others taxa. Usage of different timber species is based on the evaluation of their physical properties and also on the analysis of their main chemical properties. Thus, in order to achieve good chemical determinations, it is required an optimal methodology for sample collection of wood (SCW) in standing trees. This kind of methodologies are scarce, moreover just a few of them consider ahead of time the amount of wood needed for chemical analysis (rational sample collection) and at that at the same time they are a nondestructive sample collection (without cutting down trees). For that reason, the aim of this study was to develop a new methodology which describe SCW of conifers in a rational and nondestructive way. This SCW methodology was evaluated in Abies religiosa along of different sampling sites and consists of four steps: 1) To define the amount of wood needed; 2) To determine the basic density of wood (main parameter in the precision of subsequent calculations); 3) To estimate the volume to extract and 4) To take samples of wood in field. Our results showed that with this methodology we obtained greater amount of A. religiosa wood than the needed without showing significant differences (P>0.05) between sampling sites. In conclusion, this methodology was successful for this conifer, however future studies are required in order to determine if it can be applied in other softwood species.RESUMEN La madera ha sido un recurso natural ampliamente utilizado por la humanidad. Particularmente, la madera de coníferas destaca por su importancia ecológica, económica y distribución geográfica en comparación con otros taxa. Algunos usos de las diferentes especies maderables se basan en la evaluación de sus propiedades físicas, así como en el análisis de sus principales propiedades químicas. Para esto último, es deseable una metodología óptima para la toma de muestra de madera (TMM) en árboles en pie. Estas metodologías son escasas y pocas consideran anticipadamente en conjunto, tanto la cantidad necesaria de madera para las determinaciones químicas (toma de muestra racional) como también una toma de muestra no destructiva (sin talar los árboles). Por esta razón el objetivo del presente estudio fue desarrollar una metodología paso a paso que describa la TMM de coníferas de forma racional y no destructiva. La metodología TMM se evaluó en Abies religiosa a lo largo de diferentes sitios de muestreo y consiste en cuatro pasos: 1) Definir la cantidad de madera necesaria; 2) Determinar la densidad básica de la madera (parámetro más importante en la precisión de posteriores cálculos); 3) Calcular el volumen a extraer y 4) Tomar las muestras de madera en campo. Los resultados mostraron que la cantidad de madera de A. religiosa obtenida con la metodología fue mayor a la necesaria, sin presentar diferencias significativas (P ˃ 0.05) entre los sitios de muestreo. En conclusión, la metodología fue exitosa para esta conífera, sin embargo, se requieren estudios posteriores para determinar si podrá aplicarse en otras especies de maderas de coníferas