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Black alder (Alnus glutinosa [L.] Gaertn.) is an important component of riparian and wetland ecosystems in Europe. However, data on the growth of this significant broadleaved tree species is very limited. Presently, black alder currently suffers from the pathogen Phytophthora and is particularly threatened by climate change. The objective of this study was to focus on the impact of climatic variables (precipitation, temperature, extreme climatic events) on the radial growth of alder across its geographic range during the period 1975–2015. The study of alder stands aged 46–108 years was conducted on 24 research plots in a wide altitude range (85–1015 m) in 12 countries of Europe and Asia. The most significant months affecting alder radial growth were February and March, where air temperatures are more significant than precipitation. Heavy frost and extreme weather fluctuations in the first quarter of the year were the main limiting factors for diameter increment. Within the geographical setting, latitude had a higher effect on radial growth compared to longitude. However, the most important variable concerning growth parameters was altitude. The temperature’s effect on the increment was negative in the lowlands and yet turned to positive with increasing altitude. Moreover, growth sensitivity to precipitation significantly decreased with the increasing age of alder stands. In conclusion, the growth variability of alder and the number of negative pointer years increased with time, which was caused by the ongoing climate change and also a possible drop in the groundwater level. Riparian alder stands well supplied with water are better adapted to climatic extremes compared to plateau and marshy sites.

Norway spruce (Picea abies [L.] Karst.) and silver fir (Abies alba Mill.) are main tree species of Central Europe that are currently highly vulnerable in times of global climate change. The research deals with the effect of climate and air pollution on radial growth of silver fir and Norway spruce in mixed age-varied (56 – 146 years) forests in the Jeseníky Protected Landscape Area, the Czech Republic. The objectives were to evaluate biodiversity, structure and production, specifically interaction of radial growth of fir and spruce to air pollution (SO2, NOX, tropospheric ozone) and climatic factors (precipitation, air temperature). Concentration of SO2 and NOX had negative effect on radial growth of fir, while radial growth of spruce was more negatively influenced by tropospheric ozone. Fir showed higher variability in radial growth and was more sensitive to climatic factors compared to spruce. On the other hand, fir was relatively adaptable tree species that regenerated very well when the pressure of stress factors subsided (air pollution load, Caucasian bark beetle, frost damage). Low temperature was a limiting factor of radial growth in the study mountainous area, especially for fir. Fir was significantly sensitive to late frost, respectively, spruce to winter desiccation and spring droughts with synergism of air pollution load. Generally, older forest stands were more negatively influenced by air pollution load and climatic extremes compared to young trees.

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In Central Europe, the dynamics of mountain forests has been for a long time most influenced by wind storms. The aim of this study was to obtain knowledge about the structure and dynamics of secondary succession in extreme climatic mountain conditions on disturbed areas aft er the Kyrill Hurricane in the eastern part of the Krkonoše Mts, Czech Republic. Density, tree species and growth parameters of natural regeneration and game damage were monitored in period 2007-2018 on three localities on comparable fourteen research plots. In 2007, average number of natural regeneration reached 2,167 recruits ha-1, and 3,637 recruits ha-1 in 2018. Results showed density increase of dominant Norway spruce (Picea abies [L.] Karst.; by 65%) and the significant upturn of deciduous tree species (by 334%), especially in rowan (Sorbus aucuparia L.) during the observed period. In tree species composition, spruce share decreased from 98.4% to 92.9% in favor of deciduous tree species. In 2018, rowan, goat willow (Salix caprea L.) and silver birch (Betula pendula Roth.) accounted 1.0-22.5% of composition. In terms of height structure, the average recruit height was 44.2 cm (± 35.7 SD) in 2009 and 219.2 cm (± 135.3 SD) in 2018 with low increment in 2011, 2017 and 2018. The study also confirmed the negative influence of Calamagrostis villosa on density of the natural regeneration and positive effect of decreasing altitude and increasing slope on height increment of natural regeneration. Moreover, ungulate was significant limiting factor of growth of regeneration (31.9% damage by browsing), especially for willow and rowan (100% damage). [ABSTRACT FROM AUTHOR]