UXAFORES-Artigos
http://hdl.handle.net/10347/15615
2024-03-28T09:20:02ZComparison of two enthalpic models for the thermodynamic characterization of the soil organic matter in beech and oak forests
http://hdl.handle.net/10347/33101
Comparison of two enthalpic models for the thermodynamic characterization of the soil organic matter in beech and oak forests
Barros Pena, Nieves; Pérez Cruzado, César; Molina Valero, Juan Alberto; Martínez Calvo, Adela; Proupín Castiñeiras, Jorge; Rodríguez Añón, José Antonio
The thermodynamic characterization of the soil organic matter could be achieved by different enthalpic models little explored for soil. This paper compares two of them for calculating the enthalpy change, the Gibbs energy change and the entropy change of the soil organic matter combustion reaction, by simultaneous differential scanning calorimetry and thermogravimetry. Soil samples were collected in beech and oak forests from different geographical areas, and at different depths to represent the L/F horizon and the mineral soil, at each sampling site. The thermodynamic state variables were calculated using two different enthalpic models, to examine how they differed in relation to different types of SOM and different forest ecosystems. Both models yielded thermodynamic variables, which although closely and significantly correlated, were statistically significantly different. All the thermodynamic variables depended on the different forest types and the different nature of the soil organic matter under study. Results allowed to discern which of the models applied better to the SOM combustion reaction designed.
2023-01-01T00:00:00ZDeveloping customized fuel models for shrub and bracken communities in Galicia (NW Spain)
http://hdl.handle.net/10347/33083
Developing customized fuel models for shrub and bracken communities in Galicia (NW Spain)
Vega, José Antonio; Álvarez González, Juan Gabriel; Arellano Pérez, Stéfano; Alonso Rego, Cecilia; Ruiz González, Ana Daría
Geospatial fire behaviour and fire hazard simulators, fire effects models and smoke emission software commonly use standard fuel models in order to simplify data collection and the inclusion of complex fuel scenarios. These fuel models are often mapped using remotely sensed data. However, given the great complexity of fuelbeds, with properties that vary widely in both time and space, the use of these standard fuel models can greatly limit accurate fuel mapping. This affects fuel hazard assessment, fuel reduction treatment plans, fire management decision-making and evaluation of the environmental impact of wildfire. In this study, we developed unique customized fire behaviour fuel models for shrub and bracken communities, by using k-medoids clustering analysis based on both fuel structural characteristics and potential fire behaviour. We used an original database of 722 destructive sample plots in nine different shrub and bracken communities covering the entire distribution area in Galicia (NW Spain), one of the regions in Europe most affected by forest fires. Measurements of cover, height and fuel fractions loads differentiated by size and vegetative state (live or dead) were used to estimate the potential rate of fire spread with five different models including fireline intensity, heat per unit area and the flame length for each sampling site and considering extreme environmental conditions. The optimal number of clusters was established by combining practical knowledge about the shrubland communities under study and their associated fire behaviour, with maximization of the mean value of the silhouette variable and minimization of the within-cluster sum of squares. The structural characteristics of the medoids derived from the analysis were associated with each of the proposed customized fuel models. Finally, a simple dichotomous classification based only on shrub height was developed to enable construction of spatially explicit fuel model maps based on remotely sensed data. Thus, the methodology applied allows generation of a more realistic representation of fuel distribution in the landscape, based on fuel structure measurements of natural regional ecosystems rather than on the use of standard models. We believe that the proposed methodology is generally applicable to communities composed of other shrub and fern species in different biogeographical regions.
2024-01-01T00:00:00ZStacking factor in transporting firewood produced from a mixture of Caatinga biome species in Brazil
http://hdl.handle.net/10347/31869
Stacking factor in transporting firewood produced from a mixture of Caatinga biome species in Brazil
Antunes Santana, Otacílio; Imaña Encinas, José; Riesco Muñoz, Guillermo
The energetic requirements of the Brazilian gypsum industry are mainly provided by firewood transported by road. The cost of transporting firewood is greatly affected by the stacking factor. In this study, we determined how the stacking factor for trailer trucks varied for the firewood harvested from forest species in the Caatinga biome, Brazil. For this purpose, the following steps were carried out: i) the logs were stacked in a frame (volume, 1 stere) and weighed; ii) the solid over bark volume of each log was obtained by scanning and by xylometry (immersion in water); iii) the stacked volume of logs on the truck was measured; and iv) the stacking factor, the stacking density and the apparent density of the unpeeled wood were computed for each of 60 truck trips. The stacking factor was, on average, 1.12. This value is lower than reported for other species; the greater compaction of the timber represents an advantage in terms of transport costs. However, the maximum variation in the load weight was 20 %, which is not negligible from an economic point of view because of the associated loss of energy efficiency in the supply chain for the lowest loads.
This is an Accepted Manuscript version of the following article, accepted for publication in International Journal of Forest Engineering. It is deposited under the terms of the Creative Commons Attribution-NonCommercial License (http://creativecommons.org/licenses/by-nc/4.0/), which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited.
2023-01-01T00:00:00ZPrediction of shear strength parallel to grain in clear wood of oak (Quercus robur L.) on the basis of shear plane orientation, density and anatomical traits
http://hdl.handle.net/10347/31868
Prediction of shear strength parallel to grain in clear wood of oak (Quercus robur L.) on the basis of shear plane orientation, density and anatomical traits
Riesco Muñoz, Guillermo
Oak wood is popular for use in construction and as flooring. Evaluating the mechanical strength of oak timber is difficult and time consuming. Therefore, models for predicting mechanical properties, based on easy-to-obtain variables, may be useful. The purpose of the study was to build models for predicting shear strength parallel-to-grain in oak clear wood. With this goal, the shearing resistance was tested on 198 defect-free specimens (target dimensions 50 × 50 mm in tested section) obtained from a sample of 40 oak trees felled in north-western Spain. The mean shear strength of the sampled oak wood provenance was 15 N mm-2, which was almost equal to the highest mean value reported in previous studies. Analysis of the relationships between the variables tested enabled development of a model relating shear strength parallel to grain at 12% moisture content, with air-dry wood density and angle between tangential and shear plane as predictor variables (R2adj = 0.61, p < 0.01, bias= -0.80%, RMSE= 13.66%, for wood with wavy grain;R2adj = 0.36, p < 0.01, bias= -1.46%, RMSE= 17.22%, for wood without wavy grain). The independence of shear strength relative to the presence/absence of sapwood or the annual growth ring width was also demonstrated.
2021-01-01T00:00:00Z