J. Lousada

Proximate analysis, backwards stepwise regression between gross calorific value, ultimate and chemical analysis of wood.

The gross calorific value (GCV), proximate, ultimate and chemical analysis of debark wood in Portugal were studied, for future utilization in wood pellets industry and the results compared with CEN/TS 14961. The relationship between GCV, ultimate and chemical analysis were determined by multiple regression stepwise backward. The treatment between hardwoods-softwoods did not result in significant statistical differences for proximate, ultimate and chemical analysis. Significant statistical differences were found in carbon for National (hardwoods-softwoods) and (National-tropical) hardwoods in volatile matter, fixed carbon, carbon and oxygen and also for chemical analysis in National (hardwoods-softwoods) for F and (National-tropical) hardwoods for Br. GCV was highly positively related to C (0.79 * * *) and negatively to O (-0.71 * * *). The final independent variables of the model were (C, O, S, Zn, Ni, Br) with R(2)=0.86; F=27.68 * * *. The hydrogen did not contribute statistically to the energy content.

Characterisation of the bending stiffness components of MDF panels from full-field slope measurements

This paper deals with the characterisation of bending stiffness components of medium density fibreboard (MDF) by carrying out a single plate bending test. The approach couples full-field slope measurements with an inverse identification method. MDF panels manufactured with different fractions of Eucalyptus fibres and sugarcane bagasse particles were used. The slope maps generated across the plate surface were measured by the deflectometry technique. The curvature fields of the deformed plate were reconstructed by numerical differentiation afterwards. The virtual fields method was then implemented for material parameter identification under the framework of Kirchhoff–Love plate bending theory. The elastic properties obtained from the proposed data reduction (i.e. simultaneous identification of modulus of elasticity, Poisson’s ratio and shear modulus) were compared with values determined from classical three-point bending tests and reported in the literature. The set of properties were found in relatively good agreement.

Measurement of intra-ring wood density by means of imaging VIS/NIR spectroscopy (hyperspectral imaging)

Abstract This paper reports a novel application of hyperspectral imaging (a spectroscopic technique) for measuring wood density profiles at the growth ring scale. The measurements were performed with a spatial resolution of 79 µm. In the present case, hyperspectral imaging was used to measure wood sample reflectance for light in the wavelength range between 380 and 1028 nm, with a resolution of approximately 0.6 nm. The work was performed with 34 samples collected from 34 trees of Pinus pinea. A total of 34,093 density points were used to create and validate a partial least-squares (PLS) regression that converts spectroscopic reflectance data into density values. The coefficient of determination value between the present method and X-ray microdensitometry is 0.810 with a root mean squared error of 6.54×10-2 g.cm-3.

Management of chestnut plantations for a multifunctional land use under Mediterranean conditions: effects on productivity and sustainability

Chestnut plantations for fruit production in Northern Portugal have been subjected to intensive management system, including soil tillage, mineral fertilization and pruning. Some of these practices have no positive effect on productivity and soil–plant–water relations. Other systems (e.g., no tillage with maintenance of grass cover) have been adopted, aiming a multifunctional land use, exploiting nuts, pasture and edible mushrooms. Thus, an experimental trial was installed to assess the effects of such systems on productivity, sustainability and annual net income, as compared with the conventional system, over a six-year period. The treatments were: conventional soil tillage (CT); no tillage with permanent spontaneous herbaceous vegetation cover (NV); no tillage with permanent rainfed seeded pasture cover (NP); and as NP but with irrigation (NIP). Production of nuts, forage and edible mushrooms were measured and sustainability was assessed by production and diversity of fungal sporocarps. Annual net income was estimated by the difference between the annual gross outputs (market values for nuts, forage and edible commercial mushrooms) and the annual input costs. The greatest nut and edible mushroom production and sporocarp biodiversity were achieved in the NIP and NV and the smallest in the CT treatment. The highest annual gross output was estimated for the NV and NIP treatments, whereas the highest annual net income was obtained for the NV. No tillage with maintenance of spontaneous grass cover showed to be the most favourable management system, as it has increased productivity and biodiversity.

Effects of Recent Minimum Temperature and Water Deficit Increases on Pinus pinaster Radial Growth and Wood Density in Southern Portugal

Western Iberia has recently shown increasing frequency of drought conditions coupled with heatwave events, leading to exacerbated limiting climatic conditions for plant growth. It is not clear to what extent wood growth and density of agroforestry species have suffered from such changes or recent extreme climate events. To address this question, tree-ring width and density chronologies were built for a Pinus pinaster stand in southern Portugal and correlated with climate variables, including the minimum, mean and maximum temperatures and the number of cold days. Monthly and maximum daily precipitations were also analyzed as well as dry spells. The drought effect was assessed using the standardized precipitation-evapotranspiration (SPEI) multi-scalar drought index, between 1 to 24-months. The climate-growth/density relationships were evaluated for the period 1958-2011. We show that both wood radial growth and density highly benefit from the strong decay of cold days and the increase of minimum temperature. Yet the benefits are hindered by long-term water deficit, which results in different levels of impact on wood radial growth and density. Despite of the intensification of long-term water deficit, tree-ring width appears to benefit from the minimum temperature increase, whereas the effects of long-term droughts significantly prevail on tree-ring density. Our results further highlight the dependency of the species on deep water sources after the juvenile stage. The impact of climate changes on long-term droughts and their repercussion on the shallow groundwater table and P. pinaster’s vulnerability are also discussed. This work provides relevant information for forest management in the semi-arid area of the Alentejo region of Portugal. It should ease the elaboration of mitigation strategies to assure P. pinaster’s production capacity and quality in response to more arid conditions in the near future in the region.

Impact of the pinewood nematode, Bursaphelenchus xylophilus, on gross calorific value and chemical composition of Pinus pinaster woody biomass

The pinewood nematode (PWN), Bursaphelenchus xylophilus, the causal agent of the pine wilt disease, has been detected in several regions of Portugal affecting Pinus pinaster, a coniferous species of a great economic value. The nematodes, migrating through resin canals and feeding on parenchyma cells, induce rapid metabolic changes in ray parenchyma cells, cavitation areas, and denaturation and necrosis of parenchyma and cambial cells. To understand how anatomic changes and biochemical incidences of tree defense reactions affect the technological parameters of the wood, the gross calorific value (GCV) and chemical composition of PWN-infected and -uninfected P. pinaster wood were evaluated. The GCV was determined using Parr 6300 Automatic Isoperibol Calorimeter, and chemical composition analysis was performed by determining the contents of carbon, hydrogen, nitrogen, sulfur and Ash on complete and instant oxidation of samples by “flash” combustion. The Student’s t test with Welch correction was used for statistical data analysis. The difference between the GCV and chemical composition for PWN-infected and -uninfected P. pinaster wood was statistically significant for the GCV and for hydrogen and nitrogen contents. The carbon, oxygen, sulfur and Ash contents did not differ statistically. The GCV of PWN-infected wood varied between the highest value of hardwood and the lowest value of softwood. This interdisciplinary study stresses the important technological and economic aspects, namely the impact of PWN on wood properties and the suitability of infected P. pinaster wood for use in the wood-processing and energy industries.

Initial growth and fruiting of ‘Summit’ sweet cherry (Prunus avium) on five rootstocks

Abstract The sweet cherry (Prunus avium) cultivar ‘Summit’ still fits the standard of excellence for its typical characteristics, including large fruit size and cordate shape. This study was undertaken in Vila Real, northern Portugal, with ‘Summit’ scions raised in a nursery on five rootstocks. The orchard trials were set up in 1999, and tree growth, yield, and fruit size were monitored up to the 6th leaf. At this phase, the rootstock trunk cross‐sectional areas (TCSAs) for Maxma 14, Cab 11E, Edabriz, and Gisela 5 were 79.7%, 60.2%, 37.9%, and 29.3% of that of Mazzard, respectively. Cumulative yield was higher on Gisela 5, but it did not differ significantly from Cab 11E Maxma 14, Edabriz, and P. avium attained only 56%, 50%, and 36% of Gisela 5 cumulative yield per tree, respectively. This latter rootstock also induced higher cumulative yield efficiency when compared with the other rootstocks. Average fruit weight varied significantly according to year, rootstock, and year × rootstock interaction, which accounted for 62.6%, 13.2%, and 19.1% of the total variation, respectively. In 2002, it was Gisela 5 that permitted the cultivar to bear the best‐sized fruits (9.8g), but in 2003 (6th leaf) this rootstock produced the lowest sized fruits(10.2g). Conversely, on Edabriz, Cab 11E, and P. avium average fruit weight increased 29%, 26%, and 24%, respectively. Trees on Gisela 5 had 5.6 leaves (190 cm2) per fruit, whereas on Edabriz, Cab 11E, and P. avium they had 1.6, 2.3, and 6.4 times that value, respectively. Gisela 5 and Edabriz were very efficient in controlling vigour, having induced precocity and high cumulative yield efficiency. Leaf area/fruit ratio, however, limited fruit growth on Gisela 5, where initial high productivities demand appropriate tree nutrition to allow complete fruit, leaf, and limb growth and development on the current and subsequent season. Cab 11E was not so precocious, but proved to be productive and induced the best fruit growth. Suitable cultural practices must be adopted to fit rootstock requirements to optimise the balance between yield, fruit size, and economic value, especially for the most dwarfing.

SAZONALIDADE DO INCREMENTO EM DIÂMETRO DO TRONCO DE ÁRVORES DE Eucalyptus grandis PELO USO DE DENDRÔMETROS

O presente trabalho teve como objetivo avaliar a sazonalidade do incremento em diâmetro do tronco de arvores de Eucalyptus grandis e sua relacao com as variaveis climaticas e de fertilizacao nitrogenada e com lodo de esgoto. As arvores foram plantadas no espacamento de 3 x 2 m e fertilizadas com nitrogenio (plantio, 6, 12, 18 meses) e lodo de esgoto (plantio e 8 meses), sendo selecionadas 20 arvores de eucalipto por tratamento, de acordo com a distribuicao de area basal do povoamento, instalados dendrometros de aco no DAP e mensurado o incremento em diâmetro de fevereiro/2006 a fevereiro/2008. Os resultados permitem concluir que houve efeito das variaveis climaticas na sazonalidade do incremento em diâmetro do tronco das arvores de eucalipto, sendo observado um periodo de defasagem (lag) de 28 dias para a resposta das arvores em relacao as variaveis climaticas. Com relacao ao efeito da fertilizacao, determinou-se que o incremento em diâmetro do tronco foi maior nas arvores de eucalipto com tratamento de lodo de esgoto em relacao a adubacao mineral com nitrogenio.

Within and between-tree variation of wood density components in Pinus sylvestris at five sites in Portugal

Pinus sylvestris is widely distributed in Europe and Asia, and Portugal constitutes its westernmost limit. The reduction of the Portuguese forest area of resinous species has provoked strong constraints on wood industries supply. Therefore, an increase in Scots pine area might be important, namely by reforestations of higher altitude areas, where Pinus pinaster has great difficulties to vegetate and where the risk of pinewood nematode attack is smaller. However, large gaps remain in the knowledge of Pinus sylvestris wood characteristics growing in Portugal. To address this question, the radial wood density and growth were evaluated by X-ray microdensitometric technique, sampling 100 adult trees from five representative sites of P. sylvestris distribution area in Portugal. The results revealed that Portuguese Pinus sylvestris shows good radial growth and denser wood than those found in northern European regions. Among the Portuguese stands, sites at a lower altitude (Gerês and Marão) exhibited denser wood. Regarding density components, it was verified that the differences among sites were more significant in latewood, while the differences between trees/sites were most expressive in earlywood. These facts induce a higher genetic control in earlywood characteristics and a greater dependence of latewood components on environmental and climatic effects. Regarding growth components, Trees and Rings effects were more noticeable than Site effect. Concerning radial patterns, Portuguese Pinus sylvestris shows a downward trend in the first years after the pith, followed by an increase in latter rings for the density traits, while the radial variation of ring width is expressed by a tendency of decrease from the pith to the cambium. Compared to other European regions, Portuguese Pinus sylvestris reveals good wood quality features, namely higher density and ring width values. However, compared to Portuguese Pinus pinaster it shows a relatively lower density and identical or relatively lower radial growth. Scots pine could be a good solution for future reforestations of Portuguese mountainous areas, less favorable to other species.

RELATIONSHIP BETWEEN CLIMATE VARIABLES, TRUNK GROWTH RATE AND WOOD DENSITY OF Eucalyptus grandis W. Mill ex Maiden TREES

Climatic conditions stimulates the cambial activity of plants, and cause significant changes in trunk diameter growth and wood characteristics. The objective of this study was to evaluate the influence of climate variables in the diameter growth rate of the stem and the wood density of Eucalyptus grandis trees in different classes of the basal area. A total of 25 Eucalyptus trees at 22 months of age were selected according to the basal area distribution. Dendrometer bands were installed at the height of 1.30 meters (DBH) to monitor the diameter growth every 14 days, for 26 months. After measuring growth, the trees were felled and wood discs were removed at the DBH level to determine the radial density profile through x-ray microdensitometry and then re-scale the average values every 14 days. Climatic variables for the monitoring period were obtained and grouped every 14 days. The effect of the climate variables was determined by maximum and minimum growth periods in assessing trunk growth. These growth periods were related with precipitation, average temperature and relative air humidity. The re-scaled wood density values, calculated using the radial growth of the tree trunks measured accurately with steel dendrometers, enabled the determination of the relationship of small changes in wood density and the effect of the climatic variations and growth rate of eucalyptus tree trunks. A high sensitivity of the wood density to variation in precipitation levels was found.