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Taper models are used to determine the diameter along the trunk and allow to determine the tree trunk volume or volume of any part of it. The paper presents the method of determining the thickness of bark along the trunk using compatible taper models. Four taper models with different levels of complexity were analyzed based on data from 13 sample plots and 39 sample trees measured in black locust (Robinia pseudoacacia L.) stands from west Poland. For modelling the over and under bark diameter and bark thickness along the trunk seemingly unrelated regression of independent equations was applied. During the analyzes, the logical assumption that the thickness of the bark at any place on the trunk is determined in a difference of over and under bark diameter was applied. It was found that selected models fit the shape of the trunk with different accuracy. The worst results were obtained with the use of a polynomial model. The best fit for modelling bark thickness along the trunk was characterized by variable−form taper models. However, regardless of the complexity and quality of fit to the trunk shape, all analyzed models allowed determining the bark thickness along the trunk without systematic error and with practically acceptable accuracy.
Within the framework of work on the anatomical structure and durability features of wood, as well as analyses of radial growth, a preliminary analysis was carried out in regard to variation in the heartwood within Black locust trees. The research was carried out in three stands of straight-stemmed trees in western Poland. The variation displayed by the heartwood around its circumference and the eccentricity of the trunks was characterised with reference to: the heartwood radial index (HRI), the cross-sectional shape factor for heartwood (CSsf) and the pith eccentricity index (PEcc). The results confirmed a relationship between the degree of variation around the circumference of the heartwood and the mean age of the stands, while at the same time making clear the high level of differentiation in radial variation at the level of the individual tree. The findings suggest that the fertility of the habitat does not exert much of an influence on the generation of heartwood in Black locust trees. No statistically significant relationship was obtained when the circumferential variation of the heartwood was set against the total height or diameter at breast-height. Only in the case of crown length, and then only at the Wołów site, was there a moderate negative correlation with the coefficients of circumferential variation.
In Poland black locust grows generally in parks, gardens and along roads and in forests as well. During dendrological inventories specialists often need information about age of a tree. Simple noninvasive methods utilize mainly relation between age and size of a tree. One of such methods is mathematical formula describing relation between tree's diameter (or circumference) and its age. The main objectives of the presented paper is to elaborate such formulae for trees growing either in forests stands or in an open space (single tree, trees alley or small groups). Relations between tree's age and circumference were analyzed on the background of measured trees growing in forests administrated by the State Forests National Forest Holding from a whole territory of Poland. The formulae describing relation between tree's age and circumference were developed based on 20,302 database records for trees growing in forest stands and 6267 records for trees growing in an open space. In both cases power functions showed the best matching (tab. 1) in 95% confidence interval and which lead to construction of the age tables (tab. 2 and 3). Both elaborated formulae were tested and checked out with four series of measurement data. Three control series (1 – 'Siemianice', 2 – 'WPN' and 3 – 'Zielonka') show compatibility with analysed formulae, while the fourth one (4 – ‘Poznan') differed substantially. The probable reason of such situation lies in the fact that this series represented trees growing in urban conditions and having completely different growth rate.
Increased nitrogen deposition and biological invasions may be two crucial consequences of global change. Exotic plants often have adverse effects on native plants. However, there are reports of occasional positive interaction between them. Increased nitrogen deposition enhances nitrogen availability in soil, which may facilitate the growth of some exotic plant and decrease the competitive advantage of native plants because of their adaptation to low-nutrient environments. Consequently, increased nitrogen deposition may regulate the relationship between exotic and native plants. A greenhouse experiment was, thus, conducted to examine the effects of increased nitrogen deposition on the relationship between the native Quercus acutissima and the exotic Robinia pseudoacacia, which are both widely distributed in North China. Seedlings of both species were grown in monoculture and mixture arrangements in a pot experiment with different nitrogen addition levels (i.e., 0, 2, 5, and 10 g N m–2 a–1). Nitrogen addition altered the biomass partitioning of Q. acutissima and R. pseudoacacia seedlings, with more biomass allocated to leaves and less to roots. Although R. pseudoacacia seedlings always had growth predominance over Q. acutissima seedlings, Q. acutissima was not threatened by R. pseudoacacia at the four levels of nitrogen addition during the three-month duration of the experiment. A positive interaction between the seedlings of R. pseudoacacia and Q. acutissima was found, and increased nitrogen deposition did not affect the positive interaction. Further studies are necessary to determine whether or not R. pseudoacacia is harmful to native ecosystems and should be limited for forestation in North China.
The objective of the study was to determine the quantitative and valuable potential of wood resources of black locust (Robinia pseudoacacia) and Douglas fir (Pseudotsuga menziesii) in individual regional directorates of the State Forests (RDSFs) in Poland. We used data from the State Forests Information System database (values for the end of 2014) to determine the amount of the resources of the analysed species in forests under the State Forests management. The monetary value of black locust and Douglas fir resources was determined using both the indicator method and on the basis of sales prices of individual assortments. The occurrence, and hence the resources of black locust and Douglas fir in our country are characterized by considerable spatial diversity. Generally speaking, studied tree species are of minor importance in Polish forests as far as area and volume are concerned, but both species can the most often and in the large abundance be found in the western and northern Poland. The average sale price of wood of the tested species varied a lot in individual regional directorates of the State Forests (fig.). In the case of black locust the average sale price ranged from 99 PLN/m³ in RDSF Szczecinek to 151 PLN/m³ in RDSF Krakow, while for Douglas fir the values from 59 PLN/m³ in RDSF Łódź to 277 PLN/m³ in RDSF Katowice were obtained. The total value of black locust timber resources was assessed by the sale price method at PLN 262.4 million, and by the indicator method at PLN 186.4 million. In the case of Douglas fir timber, these values were much higher and amounted to PLN 375.0 and 309.2 million, respectively. The highest value of the studied species stands was noted in the RDSF with the largest amount of their resources.
A 60-day feeding experiment was conducted to study the effects of including 0, 20, 40, or 60 g · kg–1 leaf meal of tetraploid Robinia pseudoacacia (TRLM) in diets on performance, egg quality, and apparent nutrient and amino acid digestibility of hens. Egg mass and egg weight were both higher when feeding 40 g · kg–1 TRLM than the other three diets, the egg shape index linearly increased (P < 0.05). No significant effects of diet were seen on the other hen performance or egg quality parameters. Apparent nutrient and amino acid digestibilities increased at first and subsequently decreased with increasing inclusion of the foliage, but no significant differences were observed in dry matter or glycine. Digestibility of crude protein, ether extract, gross energy and acid detergent fibre increased up to 20 g · kg–1 TRLM and subsequently decreased, and similar trends were observed for 13 amino acids, but the digestibility of neutral detergent fibre decreased up to 40 g · kg–1 TRLM and subsequently increased. A significant linear decrease (P < 0.05) in the digestibility of proline was observed with increasing inclusion of TRLM into the diets. Tetraploid Robinia pseudoacacia leaf meal could be a potential supplementary protein source in laying hen diets at inclusion levels not exceeding 60 g · kg–1.
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