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Shater Z.,Tishreen University | De-Miguel S.,University of Eastern Finland | Kraid B.,University of Aleppo | Pukkala T.,University of Eastern Finland | Palahi M.,Castella
Annals of Forest Science | Year: 2011

Pinus brutia Ten. subspecies brutia, which occurs in the Eastern Mediterranean region, is the main forest species in Syria and important for multi-purpose forestry. In this study, 6,631 10-year past growth diameter increment measurements were taken in 83 temporary sample plots. The current breast height diameter of all trees was measured and a sample of trees was measured for height and age. The plots were placed so as to capture the whole range of variation in site quality, stand age and stand density. The data were used to develop the following models: • Dominant height model: the guide curve method was used to fit an anamorphic site index model between stand age and dominant height. • Individual-tree diameter increment model: future 10-year diameter increment was modelled as a function of site index, stand basal area, basal area of trees larger than the subject tree, slope, aspect and diameter at breast height (dbh). • Tree height model: tree height was modelled as a function of dbh, dominant height and dominant diameter. • Self-thinning: the plots which have reached the selfthinning limit were selected and the (maximum) number of trees per hectare was modelled as a function of mean diameter and site index. The set of models enables the simulation of forest stand dynamics on an individual-tree basis. © INRA and Springer Science+Business Media B.V. 2011. Source


Gonzalez-Olabarria J.R.,Center Tecnologic Forestal Of Catalonia Ctfc | Mola-Yudego B.,University of Eastern Finland | Pukkala T.,University of Eastern Finland | Palahi M.,Castella
Annals of Forest Science | Year: 2011

Introduction: This article explores the possibility of including multiple spatial scales into a mixed model for predicting the density of human-caused fire ignitions in Catalonia (North-East Spain). Methods:The location of the ignitions of all humancaused forest fires recorded in Catalonia during the period 1994-2007, including 7,847 human-caused fires, was considered as modeling data. Three spatial scales were considered in the modeling. The first or small spatial scale was defined by tiling 3,003 hexagonal plots of 1,000 ha each. The two remaining spatial scales were defined by the inclusion of the plots within municipality and county (comarca) borders. Fire ignition density was estimated at plot level using proxy variables as predictors (elevation, presence of roads, density of pathways, and dominant land-use patterns). The administrative borders of municipality and county were used to allocate the spatial variation of ignition density not explained by the plot-level estimation. Conclusions: The results of the study highlight that human-caused ignitions present clear spatial aggregation patterns at different spatial scales, and that an analysis at a single spatial scale ignores explanatory factors affecting other scales. © INRA and Springer Science+Business Media B.V. 2011. Source


Mehtatalo L.,University of Eastern Finland | Comas C.,Jaume I University | Pukkala T.,University of Eastern Finland | Palahi M.,Castella
Canadian Journal of Forest Research | Year: 2011

The diameter distribution of a forest stand is of great interest in many situations, including forest management planning and the related prediction of growth and yield. The estimation of the diameter distribution may be based on, for example, a measured sample of diameters or the application of previously estimated parameter prediction models (PPMs), which relate the parameters of an assumed distribution function to some stand characteristics. We propose combining these two information sources. The approach is adopted from the mixed-effects modelling theory. The PPMs are treated as mixedeffects models, the residuals being stand effects. These stand effects are predicted using a small sample of tree diameters with the best linear predictor. A study conducted with a Spanish pine data set showed that in a situation where the predictors of the PPM include errrors, the prediction can be improved even by using a sample plot of as few as five sample trees. Vice versa, a distribution based on a sample plot of 3-15 sample trees can be significantly improved by utilizing existing PPMs. An additional simulation study was conducted to further investigate how the violation of different underlying assumptions of the method affects the performance. Source


Lopez-Buendia A.M.,Spain Technological Institute for Construction | Lopez-Buendia A.M.,University of Valencia | Romero-Sanchez M.D.,Castella | Climent V.,Lafarge | Guillem C.,Castella
Cement and Concrete Research | Year: 2013

Surface treatments on a polypropylene (PP) fibre have contributed to the improvement of fibre/concrete adhesion in fibre-reinforced concrete. The treatments to the PP fibre were characterized by contact angle measurements, ATR-IR and XPS to analyse chemical alterations. The surface topography and fibre/concrete interaction were analysed by several microscopic techniques, namely optical petrographic, and scanning electron microscopy. Treatment modified the surface chemistry and topography of the fibre by introducing sodium moieties and created additional fibre surface roughness. Modifications in the fibre surface led to an increase in the adhesion properties between the treated fibres and concrete and an improvement in the mechanical properties of the fibre-reinforced concrete composite as compared to the concrete containing untreated PP fibres. Compatibility with the concrete and increased roughness and mineral surface was also improved by nucleated portlandite and ettringite mineral association anchored on the alkaline PP fibre surface, which is induced during treatment. © 2013 Elsevier Ltd. Source


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Castella | Date: 2016-03-30

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