Turkey oak (Quercus cerris L.) is a thermophilic oak species that is gaining importance in the context of ongoing climate change because of its better resistance to climatic extremes and drier conditions. Therefore, this article focuses on Turkey oak’s role and growth properties in the coppice forests of Southern Europe (Italy, Bulgaria) compared to similar site conditions in Central Europe (Slovakia, Czechia). The aims are to evaluate the basic dendrometry indicators, stand biodiversity, growth dynamics, and the effect of climatic factors on tree-ring increment on specific site chronologies. We found that the tree density in coppices of 50–60 years varied between 475 and 775 trees ha−1, and the stand volume ranged from 141 to 407 m3 ha−1. The complex stand diversity of all plots ranged from a monotonous to uniform structure. The size of tree-ring growth was closely related to indicators of stand density. The lowest influence of climatic factors on tree-ring growth was found in sites in Italy and the highest in Slovakia. The primary limiting factor for growth was the lack of precipitation during the growing season, especially in June and July. In contrast, temperature had a marginal effect on radial growth compared to precipitation. The radial growth in research plots in Southern Europe goes through longer 6 to 8-year growth cycles, and in Central European sites, it goes through shorter cycles of 2.4 to 4.8 years, which confirms better growth conditions in this region. The studied coppice stands exhibit a stable reaction to climate change. Yet, regarding cyclical growth, the Central European stands benefit from an advantageous climate and grow better than in Southern Europe. As part of the changing environmental conditions, Turkey oak is becoming an important tree species that can achieve high production potential even in drier habitats due to its regeneration characteristic as coppice and may play a critical role in its northerly introduction in Europe.
Bark cankers accompanied by symptoms of decline and dieback are the result of a destructive disease caused by Phytophthora infections in woody plants. Pathogenicity, gas exchange, chlorophyll a fluorescence, and volatile responses to P. cactorum and P. plurivora inoculations were studied in field-grown 10-year-old hybrid poplar plants. The most stressful effects of P. cactorum on photosynthetic behaviour were found at days 30 and 38 post-inoculation (p.-i.), whereas major disturbances induced by P. plurivora were identified at day 30 p.-i. and also belatedly at day 52 p.-i. The spectrum of volatile organic compounds emitted at day 98 p.-i. was richer than that at day 9 p.-i, and the emissions of both sesquiterpenes α-cubebene and germacrene D were induced solely by the Phytophthora inoculations. Significant positive relationships were found between both the axial and the tangential development of bark cankers and the emissions of α-cubebene and β-caryophyllene, respectively. These results show that both α-cubebene and germacrene D are signal molecules for the suppression of Phytophthora hyphae spread from necrotic sites of the bark to healthy living tissues. Four years following inoculations, for the majority of the inoculated plants, the callus tissue had already closed over the bark cankers.
The increasing probability of Taxus baccata (L.) decline given climate change brings forth many uncertainties for conservation management decisions. In this article, the authors present the effects of applying regeneration cuttings since the year 2000 on the viability of the understory yew population. By collecting data from a stand located at the centre of the largest population of European yew in Slovakia, containing approximately 160,000 individuals, and analysing tree-ring records from 38 sampled trees, the improved performance of yews, including stem growth, seed production, and number of regenerated individuals, was revealed. Thinning the canopy by removing 15% of the growing stock volume per decade, combined with the subsequent irregular shelterwood cuttings, was assessed as a useful strategy. Moreover, lower radial growth of females compared to males, but simultaneously their similar response to climate, suggests a possible trade-off between reproduction and growth. Release cuttings of up to 30% of the standing volume in the vicinity of the female trees, executed in the rainy summers following warmer winters, and consistent elimination of deer browsing, can further enhance the positive effects of applied cuts on yew viability. Overall, the suggested active measures could be considered as an effective option to preserve the unique biodiversity of calcareous beech-dominated forests in Central Europe.
Forest–steppe ecosystems represent a heterogeneous small-patch landscape important as a biodiversity hotspot and habitat for many endangered species. In this work, we examine threatened forest–steppe communities using structural indices, browsing intensity and indices that consider herbivorous game preferences. The study aims to assess the abundance of natural regeneration and the browsing intensity in relation to different stand structures and to identify woody species threatened by selective browsing at three study sites on the Krupina Plateau in the southern part of central Slovakia. At each study site, three circular permanent research plots (PRPs), each 500 m2 in size, were established for stand structure analysis. Within each PRP, nine circular subplots with a radius of 2 m were established for detailed analysis of natural regeneration. The results of this study suggest that forest patches in the forest–steppe mosaic suffer from a long-term lack of natural regeneration, which is induced mainly by increasing aridity and ungulate pressure. Positive effects on the amount of natural regeneration were noted in association with the aggregated structure of forest patches and the presence of dead wood. Differentiated stand structure influenced the regeneration number in a negative way and at the same time significantly increased browsing intensity. In relation to a more advanced regeneration, shrubs had a protective effect against browsing. The feeding preferences of the animals can positively modulate the species composition and eliminate the imbalances in the regeneration in favor of the increasingly rare Quercus pubescens Willd.