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Abstract:The paper deals with the structural diversity and production of a less frequently studied type of alder stands originated on former agricultural lands in the 1950s, established partly by plantation and partly by natural succession in the area of the Krkonoše Mts. and the Orlické hory Mts. (Czech Republic). Four permanent research plots (PRP) were established at sites where Black alder (Alnus glutinosa L. Gaertn.) and Grey alder (Alnus incana L. Moench.) naturally occurs, each plot of 0.25 ha in size. The aim of the study was to evaluate the structure and development of the alder stands with respect to biodiversity, horizontal, vertical and species structure, diameter increment with emphasis on climate factors, and the quantity and quality of timber production. The results document low diversification of the studied stands in the PRPs. The horizontal structure is defined as random and clumped at sites at the highest altitude with high water table. The number of living trees with DBH ≥ 4 cm ranges between 556 to 828 trees ha -1 with the relative stand density index (SDI) 0.67-0.77. The stand volume ranges from 247 to 393 m 3 ha -1, and decreases with higher altitudes. Low temperatures is limiting factor for radial growth in the high mountain areas, respectively low precipitation in the middle lands. Owing to a rather specific site character, as especially the spring area, the stands exhibit only average production, but the production quality is generally high. The quality timber is suitable for industrial use; the rot-affected trunk base parts usable for fuel represent only approximately 16%.

(2016). Structure, regeneration and growth of Scots pine (Pinus sylvestris L.) stands with respect to changing climate and environmental pollution. Silva Fennica vol. 50 no. 4 article id 1564. 21 p. http://dx.doi.org/10.14214/sf.1564. Highlights• Pine forest stands showed positive development of stand structural characteristics related to their diversity, number of regeneration individuals and growth characteristics.• Tree-ring width was positively correlated with precipitation, while it was negatively correlated with temperature in growing seasons.• Mean NO x concentrations showed positive effect on radial growth of pine.• Serious defoliation was caused by SO 2 concentrations and N deposition in combination with extreme climate events. AbstractChanges in the structure and development of managed Scots pine (Pinus sylvestris L.) stands with respect to changing environmental conditions were set for the period 1979-2015. The study was conducted in conditions of natural pinewoods and pine-oak sites on five permanent research plots (0.25 ha) in Eastern Bohemia, Czech Republic (CR). Studied forest stands showed positive development of stand structural characteristics related to their diversity, number of regeneration individuals and growth characteristics. The standing volume of regularly distributed tree layer in 2015 was in the range of 320-434 m 3 ha -1 , which indicates an increase by 5.9-20.0% over 10 years. Correlation between pine radial increment and the amount of precipitation was generally the strongest one. Positive statistically significant correlation between diameter increment and temperature was demonstrated only for the average March temperature of the current year. Within the CR, study site can be characterised as a medium polluted area both for sulphur and nitrogen, despite this SO 2 concentrations and N deposition in combination with extreme climate events caused severe defoliation in pine stands. Conversely, radial growth was positively significantly correlated with mean NO x concentrations. Drought mainly in combination with even medium environmental pollution can further worsen the health status of pine stands in lowland areas of Central Europe. Thus, formulation of silvicultural techniques able to mitigate the impact of these stress factors is needed.

The paper analyzes the stability and failure phenomenon of compressed thin-walled composite columns. Thin-walled columns (top-hat and channel section columns) were made of carbon fiber reinforced polymer (CFRP) composite material (using the autoclave technique). An experimental study on actual structures and numerical calculations on computational models using the finite element method was performed. During the experimental study, post-critical equilibrium paths were registered with acoustic emission signals, in order to register the damage phenomenon. Simultaneously to the experimental tests, numerical simulations were performed using progressive failure analysis (PFA) and cohesive zone model (CZM). A measurable effect of the conducted experimental-numerical research was the analysis of the failure phenomenon, both for the top-hat and channel section columns (including delamination phenomenon). The main objective of this study was to be able to evaluate the delamination phenomenon, with further analysis of this phenomenon. The results of the numerical tests showed a compatibility with experimental tests.

The Jizerské hory Mts. (the Czech Republic) are part of the Black Triangle region strongly affected by a decline and dieback of Norway spruce (Picea abies [L.] Karst.) stands since the 1970s. In the studied peaty spruce stands in the summit parts of the Jizerské hory Mts., the health status, radial growth and foliar nutrient content in relation to air pollution (SO 2 , NO X and O 3) and climate factors (temperature, precipitation) were investigated in 1960-2015. A considerable disturbance of the stand structure induced by an increased mortality was observed in 1981-1983 when more than a half of the tree individuals died. Severe defoliation occurred in 1981 as a consequence of the synergic effects of air pollution, winter desiccation and spruce bark beetle outbreak, as well as in 2015 due to the drought and high temperatures. Tree ring analyses indicated significant growth depression in 1979-1987, a period of the highest SO 2 load, and in 2010-2015. Foliation and diameter increment were significantly influenced by SO 2 and NO X concentrations, the maximum daily concentration being the most negative factor; no significant correlation of the ozone exposure was detected, though. Foliar analyses also document significant negative impacts of air pollutants on the nutrient status of forest stands, mainly in the increase of the sulphur level. Since 1990, a significant increase in calcium and magnesium has been observed, as a result of forest liming. Interaction between radial growth and temperature was stronger compared to precipitation. Low temperatures and high precipitation in growing season were the limiting factors for radial growth in waterlogged mountain areas.