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The work concerned the ascomycetous fungus Eutypella parasitica, which for several decades has been present in North America, where it attacks various species of maple. In 2005, for the first time it was recorded in Europe, in Slovenia. Later on it was found in Austria, Croatia, Germany, Hungary and the Czech Republic. In 2016 for the first time the species was reported in Poland, in the Polish−Czech border region. The work includes fieldwork and laboratory research on disease symptoms and the causal pathogen. The research was conducted in August 2016 in the Ustroń Forest District. In 16 randomly selected stands, the health of Acer spp. trunks was analyzed, especially in terms of Eutypella parasitica infection. Of the 16 trees, where extensive necrosis and cankers were found, the material was collected for laboratory analyses. In the laboratory, the fruit bodies of fungi on necrotic lesions were examined and the fungi isolates were performed on 2% malt−agar extract. Identification of representative E. parasitica isolates was confirmed based on the ITS rDNA sequence. Within the 16 stands, where the maples were analyzed, individuals with symptoms of trunk infestation by E. parasitica were found in 8 stands. Based on in situ produced fruiting bodies and isolated cultures, the presence of E. parasitica was finally confirmed on 14 trunks, including 13 Acer pseudoplatanus trunks and one A. campestre. All cankers were located in the butt section of the trunk, below 3 meters, reaching from 21 to 252 cm in length. Fungal fruit bodies were present within the necrotic lesions. Morphological characteristics of asci, ascospores and colonies isolated on malt−agar extract are given. The phytosanitary risk for Acer pseudoplatanus and other maples is also discussed. Moreover the preliminary actions that should be taken by the foresters are indicated.
The processes determining the formation and structure of grassland community are realised at threee levels: the genetic individual (genet, clone), the population and the community. Clonal plants are the dominant species in a grassland community. Clonal growth, modular structure of the plants, as weil morphological and physiological properties and adaptations such as: modification of shoots to form stolons and rhizomes, morphological and physiological integration of modules (ramets), disintegration of the clone and independence of rooted ramets, and growth and death of ramets in the life cycle of clonal plants, inlfuence the life span of the genet, the way of the clone's spreading and the position in the community. The above traits have a significant influence on the regeneration of plants after mowing and grazing, as weil as on the resistance to environmental disturbances. The possibility of increased population abundance through generative and vegetative reproduction is a characteristic trait of clonal plants. Clonal growth of plants, the pattern of spatial formation of the clone, interactions and reciprocal compromises between the species in the neighbourhood have a significant influence on the coexistence of various species in a grassland community. Clonal plants are adapted to mowing and grazing. The abandonment of seminatural grassland causes unfavourable changes to the community structure and its species composition.
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