The most extensive study to be carried out in Poland, and one of only a few worldwide, regarding the influence of location, tree age and forest habitat type on the basic fuel properties of silver birch (Betula pendula Roth.) wood was conducted in 12 Forestry Districts of the Polish State Forests. The field study included trees in three age groups of approximately 30, 50 and 70 years. The research was carried out in a fresh broadleaved forest (FBF) habitat type, where in Poland silver birch stands predominate in respect of coverage area and merchantable volume. Additionally, for five selected Forestry Districts, a comparative study was conducted in a fresh mixed broadleaved forest (FMBF), the second most important habitat of this tree species. A total of 306 test trees were examined. For every sample, calorific value and contents of ash, carbon, hydrogen, nitrogen, sulphur and chlorine were determined. The results indicated a statistically significant influence of location on the calorific value (p = 0.0001) and on the contents of ash (p < 0.0001), carbon (p < 0.0001), hydrogen (p < 0.0001), nitrogen (p < 0.0001) and chlorine (p < 0.0001) in the analysed wood. Moreover, statistically significant differences were observed between values of ash content (p = 0.046) and of calorific value (p = 0.0026) depending on the forest habitat type. Tree age was found to have no significant influence on the calorific value of silver birch wood.

The article presents the results of a so far most extensive study on the effect of tree age on variation of the chemical structure of silver birch wood carried out in Poland. Field studies took place in 12 forestry districts distributed throughout the country. In each district, study sites were selected with stands aged approximately 30, 50, and 70 years in fresh broadleaved forest habitats, as well as in five districts in fresh mixed broadleaved forest habitats. Analyses were made of the contents of substances soluble in cold and hot water, ethanol and 1% NaOH, as well as the contents of cellulose, lignin, pentosans and ash, and the pH, of wood from 306 silver birch trees. Tree age was shown to have a significant effect on the contents of cellulose, pentosans, ash, and substances soluble in 1% NaOH. In the case of the other characteristics, age was found to have no significant effect. The cellulose content was lowest in 30-year-old stands and increased with tree age. Similar observations were made regarding ash content. Contents of pentosans and substances soluble in 1% NaOH were highest in the wood of the youngest trees. Since birch wood is used by the pulp and paper, board and energy industries, the knowledge of its chemical composition, depending on the age of the trees, can be of potential practical importance for its further application.

We report on the most extensive study to date in Poland concerning the variability in the chemical composition of silver birch (Betula pendula Roth.) wood depending on the forest habitat type and the location of the forest stand. The research was carried out in 12 forest districts, on two habitat types where silver birch forest stands predominate in respect of coverage area and merchantable volume. Chemical composition analysis was performed on 51 samples from 306 test trees aged approximately 30, 50 and 70 years. In the examined sample material, the sum of the main chemical components for individual locations varied from 89.26 to 91.57%. The content of substances soluble in water and ethanol ranged from 2.30 to 4.03%, and the ash content was measured at between 0.09 and 0.25%. The results showed that the location had a significant influence on the contents of substances soluble in cold water (p = 0.0015), hot water (p = 0.0005), ethanol (p \ 0.0001) and 1% NaOH (p = 0.0014), as well as on the contents of cellulose (p = 0.04), lignin (p = 0.002), pentosans (p = 0.04) and ash (p \ 0.0001) and on the pH value (p \ 0.0001). Notable influence of location on the contents of secondary constituents of birch wood, especially those extractable with water and ethanol, was recorded for the test plots in north-eastern Poland. The obtained results may form a basis for assessment of the industrial utility of birch wood, as well as the optimisation of traditional methods of utilisation and the development of new such methods that are ecological and sustainable.

Centre Scientifique de l'Académie Polonaise des Sciences à Paris est une unité scientifique auxiliaire de l'Académie Polonaise des Sciences (APS/PAN). Sa mission principale est de contribuer à promouvoir en France les travaux issus de la recherche polonaise et de développer les coopérations scientifiques et culturelle franco-polonaises. L'origine historique du centre remonte à la Grande Émigration polonaise en France (XIX e siècle) mais son origine directe est constituée par la séparation en

Large quantity of residual biomass with possible energy and industrial end can be obtained from management operations of urban forests. The profitability of exploiting these resources is conditioned, by the amount of existing biomass within urban community ecosystems. This research was focused on direct and indirect quantification of lignocellulosic waste from urban tree pruning. The treated species, Morus alba, Platanus hispanica, Sophora japonica, Phoenix canariensis and Phoenix dactilifera are widely deployed as ornamental vegetation in Mediterranean countries. Mathematical models for predicting the available amount of pruning residues for each species were developed from easily measurable dendrometric parameters, such as diameter at breast height, crown diameter, total tree height, obtaining coefficients of determination between 0.67 and 0.96. These models can be used for urban inventories and the application of logistic models. On the other hand, Terrestrial Laser Scanner (TLS) technology was applied to improve the estimates of tree architectural parameters obtained by ground-level observations at individual tree level. For this, apparent crown volume was calculated by 4 different methods: global convex hull for the entire point cloud that forms the crown; convex hull by layers of 5cm height in the XY plane; triangulation by XY flat sections, and discretization of the point cloud in small elements of volume (voxel). Finally, residual biomass for each species was classified and characterized according to the UNE norms, including dimensional analysis of the obtained materials, density, moisture content, calorific value as well as carbon, nitrogen, hydrogen, and sulfur content. Models to predict the gross calorific value from the elemental composition were developed for fast indirect determination in industry.PhD Thesis Magdalena Sajdak IX RESUMEN Una gran cantidad de biomasa residual con posible uso energético e industrial puede ser extraída de las operaciones de gestión de los árboles ornamentales de las ciudades. La rentabilidad del aprovechamiento de estos recursos está condicionada por la cantidad de biomasa existente en los ecosistemas urbanos. Esta investigación se ha centrado en la cuantificación directa e indirecta de los residuos biomásicos de la poda de árboles urbanos ornamentales. Las especies estudiadas fueron Morus alba, Platanus hispanica, Sophora japonica, Phoenix canariensis y Phoenix dactilifera las cuales son ampliamente utilizadas como vegetación ornamental en los países mediterráneos. Modelos matemáticos para la predicción de la cantidad residuos de poda disponible han sido desarrollados para cada especie a partir de parámetros dendrométricos de fácil medición, tales como diámetro del tallo a altura del pecho, diámetro de copa o altura total, resultando coeficientes de determinación entre 0.67 y 0.96. Estas ecuaciones pueden ser utilizadas para los inventarios urbanos y la aplicación de los modelos logísticos. Por otra parte, se han analizado técnicas de escaneado con láser terres...