Orthotropic hygric and mechanical material properties of oak wood

The present study examines the three-dimensional hygric and mechanical behavior of oak wood. The moisture equilibrium state, characterized by the sorption isotherms, was obtained from measurements taken during adsorption and desorption cycles. Sorption behavior was analyzed with the Dent theory and compared considering the sorption direction (adsorption/desorption cycle). Sorption parameters were provided for possible numerical applications in hygric material models. The corresponding swelling and shrinkage behavior was examined and characterized by the moisture expansion parameters for all anatomical directions. Orthotropic mechanical material behavior was characterized by determining the elastic engineering (Young's moduli, shear moduli, and Poisson's ratios) and the bending, compressive and compressive shear strength material parameters. Influence of moisture content (MC) on the mechanical material properties was studied using Young's moduli, Poisson's ratios, and the investigated strength parameters. A significant difference between the sorption behavior in adsorption and desorption, known as the hysteresis effect, could be proved. Furthermore, swelling and shrinkage behavior did not show any dependency on the adsorption/desorption cycle. The results confirm the significant influence of MC on the Young's moduli and the strength properties, however, did not validate an influence on the Poisson's ratios.     

Habitat prediction model for three-toed woodpecker and its implications for the conservation of biologically valuable forests

We studied habitat selection of three-toed woodpecker (TTW) in relation to forest structural variables, habitat types and hydrological conditions in north-eastern Poland. Based on known locations of 34 breeding pairs and the data on location of forest areas with high conservation value (referred to as Biologically Important Forests), we created a habitat prediction model for TTW using a Maxent algorithm. We found that this species most often selected breeding sites characterized by high contribution of old-growth stands with uneven vertical structure and considerable amount of very old trees of previous generations, as well as boreal spruce-dominated bogs and riverine forests. Such sites were preferred regardless of their actual protection status, which leads to the following conclusion: although existing forest reserves are very important to three-toed woodpecker, suitable habitats with similar characteristics can still be found outside protected areas and are also utilized by the species. However, such sites outside reserves are threatened by fragmentation due to timber extraction. Therefore it is recommended to protect these sites by either including them into existing reserves or putting them under special management schemes.     

Allometric equations for estimating the mass and volume of fresh assimilational apparatus of standing scots pine (Pinus sylvestris L.) trees

The increment of trees depends, primarily, on the size of the assimilation apparatus of the crown and its efficiency to produce organic matter. That is why this study undertook to determine the size of the assimilation apparatus of single trees of Pinus sylvestris L. The authors used the mass (ugc) and volume (ugo) of twigs covered with needles in order to estimate the size of the assimilation apparatus. The performed analysis revealed a significant correlation between easy-to-determine tree variables: breast height diameter—d_1.3, height—h and age—w and the ugc and ugo. This correlation served as a basis for the elaboration of equations which allow determining the size of the assimilation apparatus. The empirical material was provided by the results of measurements carried out on 1808 pine trees growing in mesic forest sites typical for this species in western Poland.     

Responses of Acer saccharum canopy trees and saplings to P, K and lime additions under high N deposition

Heavy atmospheric nitrogen (N) deposition has been associated with altered nutrient cycling, and even N saturation, in forest ecosystems previously thought to be N-limited. This observation has prompted application to such forests of non-N mineral nutrients as a mitigation measure. We examined leaf gas-exchange, leaf chemistry and leaf and shoot morphological responses of Acer saccharum Marsh. saplings and mature trees to experimental additions of non-nitrogenous mineral nutrients (dolomitic lime, phosphorus + potassium (P + K) and lime plus P + K) over 2 years in the Haliburton region of central Ontario, which receives some of the largest annual N inputs in North America. Nutrients were adsorbed in the mineral soil and taken up by A. saccharum trees within 1 year of fertilizer application; however, contrary to expectation, liming had no effect on soil P availability. Saplings and canopy trees showed significant responses to both P + K fertilization and liming, including increased foliar nutrient concentration, leaf size and shoot extension growth; however, no treatment effects on leaf gas-exchange parameters were detected. Increases in shoot extension preceded increases in diameter growth in saplings and canopy trees. Vector analysis of shoot extension growth and nutrient content was consistent with sufficiency of N but marked limitation of P, with co-limitation by calcium (Ca) in saplings and by Ca, Mg and K in canopy trees.     

Mineral nitrogen fertilisers remain a crucial factor even in the ecological intensification of agriculture

The negative impact on the environment caused by intensive agriculture has been extensively discussed for years. In particular, excessive nitrogen application has been associated with biodiversity loss. Many studies have shown the potential to reduce the use of nitrogen without any impact on crop yield. Maintaining crop yield has been the goal, whereas crop quality has not been considered. In this paper, we investigate the effect of the level of soil organic carbon (SOC) and nitrogen fertiliser application on winter wheat (Triticum aestivum) yield and its quality. We show that the absence of nitrogen fertiliser decreased both yield and quality parameters of cereal grain. Quality parameters, such as protein and gluten contents, zeleny value, falling number and hardness were strongly positively influenced by nitrogen fertiliser application. The SOC level had no significant effect on these grain quality parameters. As a result, in the absence of nitrogen fertiliser, grain was not suitable for baking bread. We recommend that in the debate on the potential to limit the use of nitrogen in agricultural production, its impact on grain quality should be taken into consideration, especially at low levels of SOC.     

The effects of forest patch size and ownership structure on tree stand characteristics in a highly deforested landscape of central Poland

Forest structure is influenced by the origin, history and manner of forest management. All these aspects may affect the occurrence of many forest dwelling organisms. We investigated the simultaneous impact of forest patch size and ownership structure on selected forest characteristics in central Poland. We sampled stand composition, the DBH of particular tree species, basal area, species number and species diversity in all 32 forest patches found in a farmland-dominated area of 150 km². Forest ownership status was linked to patch size: large patches were state-owned and small ones were private. Ownership status also affected the average DBH and basal area of all tree species pooled, with lower DBH and basal area found in private forests. The share of deciduous trees was negatively affected by forest size, while pine was positively affected, which could suggest that forest management and economic interests may be related to this factor. The share of non-native species was higher in state forests. Our results showed that forest patch size could be associated with its ownership status, which is commonly ignored in research on the relationship between forest size and species occurrence. Historical as well as sociological aspects related to private forests in Poland are also presented.     

Forest as a place for recreation but also the source of allergenic plant pollen: to come or avoid?

For many years, we have observed a significant rise in urban population, the spatial development of cities, and an increase in urbanized areas. More and more people feel the need to have contact with nature. The interest in forest recreation is growing, though the forest is a serious source of allergenic plant pollen. The aim of the present study was to compare two forest types in the context of their recreational potential and the effect strength of aeroallergens. This study was conducted in SE Poland in a Nemoral Scots pine forest (RB) and in a Central European submountainous beech forest (TH). Their recreational potential was assessed. Samples of moss containing plant pollen were collected under the canopy, from forest clearings and forest edges as well as in an open area. Based on the number of pollen grains deposited in moss pollsters, the forest impact on humans was calculated. The recreational potential values for both sites studied are evidence of the high recreational suitability of these forests, but the recreational capacity of RB is lower compared to TH. Palynological analysis showed that the pollen deposition is higher in BR and that the plant pollen risk is lowest under the canopy, regardless of the forest type. The beech forest was found to be characterized by greater recreational potential and a weaker actual effect of pollen allergens than the pine forest. In assessing forest recreational potential, palynological data should form the basis for modification of the degree of recreational suitability. Such information would also be useful in controlling recreational traffic since, as we have proved, visiting appropriate places in a forest allows the exposure of allergen sensitive people to be reduced.     

The epidemiology,molecular characterization and clinical pathology of circovirus infections in pigeons – current knowledge

The first cases of circovirus infections in pigeons were documented less than 25 years ago. Since then, circovirus infections have been reported on nearly all continents. The specificity of pigeon breeding defies biosecurity principles, which could be the reason for the high prevalence of PiCV infections. PiCV infections in pigeons lead to atrophy of immune system organs and lymphocyte apoptosis. Infected birds could be more susceptible to infections of the respiratory and digestive tract. PiCV has been associated with the young pigeon disease syndrome (YPDS). PiCVs are characterized by high levels of genetic diversity due to frequent point mutations, recombination processes in the PiCV genome and positive selection. Genetic recombinations and positive selection play the key role in the evolution of PiCV. A protocol for culturing PiCV under laboratory conditions has not yet been developed, and traditional vaccines against the infection are not available. Recombinant capsid proteins for detecting anti-PiCV antibodies have been obtained, and these antigens can be used in the production of diagnostic tests and subunit vaccines against PiCV infections. However, YPDS has complex etiology, and it remains unknown whether immunization against PiCV alone will contribute to effective control of YPDS.     

Effects of short-term thermomechanical densification on the structure and properties of wood veneers

The effects of short-term thermomechanical (STTM) densification temperature and pressure on the changes in surface roughness, wettability, mass loss (ML), thickness and density of alder, beech, birch, and pine wood veneer with low moisture content (~5%) were investigated. The anatomical structure of veneers was also observed. Veneer sheets were densified using pressure levels of 4, 8 and 12 MPa at three temperatures: 100°C, 150°C and 200°C for 4 min. The results were compared with those of the non-densified veneers. The obtained results show that STTM densification of veneers similarly to long-term densification of solid wood causes irreversible changes in their properties. The STTM-densified veneer surfaces became smoother and more hydrophobic, ML increased slightly while roughness and thickness values decreased significantly, the cell lumens collapsed and a certain amount of fractures in cell walls developed with increasing densification temperature and pressure. All of the investigated wood species showed higher density values after densification. It was found that an even STTM densification of veneers provides stable properties under normal atmosphere conditions; in particular, the thickness and contact angle values were stable for 24 hours after densification, which is an important consideration for industrial applications.