The main objective of this study was to reveal variations in the wood structure and to define the location of the boundary between juvenile and mature wood Larix decidua Mill. from fast growing tree plantations. To reach these findings, the samples of wood from four short-rotation plantations in Central Europe (Poland) were selected and compared. The procedure used to determine the demarcation point between juvenile and mature wood resulted in strong correlations between the width of growth rings and the initial cambial age. It was found that the structure of wood from fast-growing trees differs from commercially available timber. The wood derived from plantations revealed wider annual rings than wood from natural forests. The analysis of the variability of wood structure resulted in defining the location of the boundary between juvenile and mature wood. Based on the analysis of structure of annual rings, the boundary of juvenile wood in fast-growing larch is placed between the 12th and 15th annual ring. The investigated material contained high proportions of juvenile wood, which makes up more than 70% of trunk volume. On the microscopic level, no visible changes, indicating the presence of a mature wood zone, were found.
It was shown that incising of veneers (60 -15 m/m 2 ) prior to plywood bonding allowed reduction of pressing time by 8 -9% for a pressing temperature of 90ºC when compared to the controls. Nevertheless, with pressing temperatures lower than normal and shortened pressing times the shear strengths of the plywood met the requirements of the respective standards.
The effects of traditional tillage cultivation (control treatment), no tillage (instead of tillage the soil was loosened with scruff), and direct sowing (with a special drill into unploughed soil) on the health of spring barley cultivar. Klimek were compared in three-field crop rotation (field bean, winter wheat, spring barley) in an experiment performed in the years 1997-1999 on the soil of a good wheat complex. The results of phytopathological observations carried out over the vegetation season are presented in the form of an injury index. The following diseases were recorded on spring barley: net blotch (Drechslera teres) - net type and spot type, powdery mildew (Blumeria graminis), leaf blotch (Rhynchosporium secalis), eyespot (Tapesia yallundae) and foot rot (fungal complex). Tillage system had no a significant influence on the occurrence of both types of net blotch. The intensity of powdery mildew and leaf blotch was the highest in the case of traditional tillage cultivation, and the lowest - in that of no tillage. Direct sowing was conductive to the development of eyespot, and no tillage - to foot rot. Fungi of the genus Fusarium, mainly F. culmorum, and the species Bipolaris sorokiniana, were isolated most frequently from infested stem bases. The weather conditions differed during spring barley grown in the three years analyzed. Mean air temperature in 1997 and 1998 was similar to the many-year average for the city of Olsztyn and its surroundings (13.8°C). In the vegetation season 1999 mean air temperature reached 14.6°C, and was considerably higher than the many-year average. Taking into account total precipitation and distribution in the three-year experimental cycle, 1997 and 1998 can be considered average, and 1999 - wet.The weather conditions had a significant effect on the intensity of all diseases observed on spring barley. The highest yield grain was obtained in the case of traditional tillage cultivation (on average 3.06 t·ha-1 for the three years analyzed), and the lowest - in that of direct sowing (2.18 t·ha-1). No tillage occupied a middle position (2.55 t·ha-1)
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