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The role of socioeconomic factors influencing the dietary habits of students of medical academies was analysed. The following factors were considered: social class, socioeconomic status, place of residence. The study was carried out among students of the medical academies in Gdansk, Poznan and Warsaw. Of the analysed factors the greatest differentiating influence on the dietary habits was exerted by the residence during the studies and economic status. Students living in students’ hostels or private rooms and having lower economic means had less adequate dietary habits. The abnormalities included, in the first place, irregularity of meals, lower number of meals with animal, protein lower frequency of consumption of fruit, vegetables and coarsely ground cereals.
The study compared basic density, compressive strength along the grain, static bending strength and modulus of elasticity of juvenile wood in pines from different Kraft’s classes. Analyses were conducted in 8 mature pine monocultures in north-western Poland. In each experimental site a total of 9 trees were selected, thus the analyses were conducted on 72 model trees (with 24 for each social class of tree position in the stand). The highest values of analysed technical parameters were recorded for wood of co-dominant trees, the lowest were found for predominant trees, while intermediate values were recorded for wood of dominant trees. All the reported differences were statistically significant. Similar dependencies were observed when comparing wood from different sections of stems, with the greatest disproportions, frequently statistically significant, found in their lower sections.
Presented analyses were connected with modelling foliage biomass of Scots pine (Pinus sylvestris L.) growing in northern and western Poland. In order to realize the study, a total of 38 one-hectare experimental plots were established in commercial pine monocultures growing on sites optimal for this species at a given geographical location. A total of 114 trees aged 32-114 years were felled and their needle weight and the weight of needles and young, 1-year old twigs were measured. Since social variation in the stand could affect the fit of the model, for each social class of tree position an individual allometric equation was proposed, based on easily measurable biometric traits of trees. Analysis of stepwise backward regression was conducted in order to determine variables in these equations. It turned out that to estimate foliage biomass of predominant and dominant trees, it seems most appropriate to apply diameter at breast height and tree age. In turn, for co-dominant trees, apart from diameter at breast height and tree age, the model needs to include additionally tree height and crown length. Moreover, due to the fact that the dependence between needle weight and the weight of needles and young twigs is practically linear, prediction was conducted for the biomass of foliage with young twigs. From the practical point of view, this makes it possible to precisely determine needle biomass on the basis of the weight of needles with young, 1-year-old shoots.
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