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    Dendrochronological data from twelve countries proved definite growth response of black alder (Alnus glutinosa [L.] Gaertn.) to climate courses across its distribution range
    (Sciendo, 2022) Vacek, Zdenek; Vacek, Stanislav; Cukor, Jan; Bulusek, Daniel; Slavik, Martin; Lukacik, Ivan; Stefancik, Igor
    Black alder (Alnusglutinosa [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.
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    Effect of InvasiveRhododendron ponticumL. on Natural Regeneration and Structure ofFagus orientalisLipsky Forests in the Black Sea Region
    (Mdpi, 2020) Vacek, Zdenek; Vacek, Stanislav; Esen, Derya; Yildiz, Oktay; Kral, Jan; Gallo, Josef
    Biological invasions threaten global biodiversity and forest ecosystems; therefore, it is necessary to use appropriate strategies for combating the spread of invasive species. Natural regeneration of eastern beech (Fagus orientalisLipsky) is considerably limited by an aggressive invasive shrub, pontic rhododendron (Rhododendron ponticumL.), in the Black Sea Region of Turkey. Therefore, the future character of the region's forests is uncertain. The aim of this research was to evaluate the structure of beech forests with different management regimes of rhododedron and to determine the interaction among tree layer, rhododendron cover, and natural regeneration in Duzce Province using the FieldMap technology. The following variants of forests were compared: without intervention (control) and three and six years after rhododendron clearance. The results showed that tree density ranged between 175-381 trees ha(-1)and stand volume between 331-589 m(3)ha(-1). The horizontal structure of the tree layer was mostly random, and the spatial pattern of natural regeneration was aggregated. Recruit density and height in the beech stands were significantly differentiated due to the influence of presence or absence of invasive rhododendron. Rhododendron cover ranged between 81%-97%, and woody stems amounted to 72,178-86,884 ha(-1)in unmanaged forests. Canopy in the overstory did not have a significant effect on the density of regeneration and rhododendron cover. Tree layer had a significant negative influence on natural regeneration within a 4 m radius on the plots without rhododendron. However, on the plots with dense rhododendron cover, tree layer had a positive influence on regeneration within a 1.5 m radius. Natural regeneration density was significantly higher when rhododendron was cleared than the plots without intervention. On the plots without woody clearance, there was an insufficient regeneration (113-619 recruits ha(-1)); however, they had higher mean height compared to the sites without rhododendron. After three and six years of rhododendron clearance, the numbers of recruits in natural regeneration were 63,981 ha(-1)and 105,075 ha(-1), respectively. In conclusion, invasive spread of rhododendron was a limiting factor of the prosperous regeneration and tree species diversity, and manual clearance of rhododendron is recommended in managed beech forests of the study region.
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    European Ash (Fraxinus excelsior L.) Dieback: Disintegrating forest in the mountain protected areas, Czech Republic
    (Osterreichischer Agrarverlag, 2015) Vacek, Stanislav; Vacek, Zdenek; Bulusek, Daniel; Putalova, Tereza; Sargıncı, Murat; Schwarz, Otakar; Moser, W. Keith
    European ash (Fraxinus excelsior) is an important tree species in most temperate forests in Europe. Its future is threatened however, especially by an invasive fungus, Hymenoscyphus fraxineus (Hymenoscyphus pseudoalbidus, Chalara fraxinea). The current study is focused on the health of ash in the Krkonose Mountains National Park, Czech Republic. On permanent research plots containing mixtures of ash and other species, the stands' health condition was evaluated annually in 2009-2015, by using radial increment and foliage of 350 trees as indicators, with emphasis on the cenotic arrangement and morphological type of the crown. The results show mean annual decrease in foliation of 1.6-2.7% for live trees and 2.4-4.6% in all live and dead trees, with an overall mortality of 16.3% of trees. During the latter half of the study, the defoliation dynamics and dieback accelerated, especially at lower altitude and waterlogged sites. In 2012-2015, the mean annual decrease in foliation reached 3.9% in live trees and 6.3% in all trees. The mean radial increment was significantly lower 2 years after the purported fungi attack and the mean foliage density was significantly lower 6 years after the attack compared to healthy trees. Based on the evaluation of the results and the literature, a set of practical guidelines was established for management strategies and conservation of threatened European ash in similar stand conditions.