Th is study explores the invasive alien fl ora of Lozenska Mountain, southwestern Bulgaria (maximum height 1190 m, area 80 km 2 ). Th e aims were to (i) describe the taxonomic and ecological structure of the invasive alien fl ora in Lozenska Mountain, and (ii) provide data on the local distribution of the globally most widespread invasive species. Ten transects of diff erent lengths (from 4 to 12 km) in diff erent parts of the mountain covering the most characteristic habitats were surveyed between April 2017 and October 2018. Altogether, 27 invasive alien species (IAS) and 4 potentially invasive alien species (PIAS) belonging to 17 families of fl owering plants were encountered. Th ese represent 3.46% of the fl ora of Lozenska Mountain, and 45% of all the IAS in Bulgaria. Seven species (Acer negundo, Ailanthus altissima, Amorpha fr uticosa, Bidens fr ondosus, Fallopia × bohe mica, Opuntia humifusa and Robinia pseudoacacia) are highly aggressive. In the biological spectrum of IAS, therophytes predominate (29%), followed by hemicryptophytes (19.4%). Th e majority of IAS originates from America (65.6%) and Asia (19.5%). 64.5% of the IAS were deliberately introduced. Th e established invasive species on the territory of the mountain are predominantly heliophytes (90.3%); microthermophytes (71.0%); high humidity species (38.7%); mesophytes (54.8%), mesooligotrophs (58.1%) and basophilic species (80.6%). Th e most widespread species are Robinia pseudoacacia, Erigeron canadensis and Xanthium italicum. Most of the IAS were found in one transect only. Th e highest percentage of species cover (over 80%) was reached by plants adapted to specifi c habitats: aquatic (Elodea canadensis), riparian (Impatiens glan dulifera, Fallopia × bohemica) and anthropogenically heavily disturbed terrains (Sorghum halepen se). Th ere is a substantial threat of IAS irruption on the territory of Lozenska Mountain for the following habitat types (reference codes according to Annex I of the Directive 92/43/EEC): 3150 (Natural eutrophic lakes with Magnopotamion or Hydrocharition vegetation) and 3270 (Rivers with muddy banks with Chenopodion rubri p.p. and Bidention p.p. vegetation) included in Natura 2000.
In the last decades, invasive plant species have rapidly settled on the islands in the Danube River. This process is closely related to anthropogenic activities, such as felling and cultivation of soil for affor-estation of Euro-American poplar trees throughout the Danube River basin. In this regard, it is im-portant to: (i) determine the speed and scope of invasive vegetation establishment and (ii) determine more precisely the ongoing successional dynamics. Monitoring in permanent plots is needed to track the changes and assist in decision-making processes for the management of protected areas on the islands in the Danube River. The aim of the study is to describe and justify an innovative approach to analyse the dynamic of the invasion species occurrence and development as related to site conditions and management across the islands in the Danube River. The following methodological approach was considered: (1) selection of islands with well-preserved and sufficient in area covered by natural forest vegetation; (2) differentiation of strata by forest type, age and canopy cover; (3) setting up permanent sample plots for long-term monitoring in natural riparian forests.
In 2020, the health status of urban forests in Etropole and Pravets municipalities was monitored based on remote sensing data and field assessment. The study provides information for early detection and identification of pests and pathogens causing damage in different forest types. Three forest stands were assessed: Scots pine (Pinus sylvestris) plantation near the town of Etropole, European beech (Fagus sylvatica) natural stand near Etropole Monastery, and Quercus spp. coppice stands in ‘Nebesnite Pasbishta’ forest park near Osikovitsa village. In two sample plots (town of Etropole and Osikovitsa village), remote sensing data were obtained by a ‘Parrot Sequoia’ multispectral camera integrated with a specialized professional system eBee ‘Flying Wing’. Normalised difference vegetation index (NDVI) was assessed by digital mixing of imagery, captured in the red and near-infrared range. It was established that the Scots pine plantations were weakened, with NDVI values between 0.66 and 0.75. The oak stands in the area of Osikovitsa village were in better health condition (NDVI mainly 0.79-0.98). Symptoms of diseases and pest damage were found during the field verifications. Severe deterioration caused by the invasive fungal pathogen Dothistroma septosporum had destroyed the pine plantation near Etropole. The pathogen caused premature needle defoliation, resulting in loss of timber yield and, in severe cases, tree death. In oak stands, damage was caused mainly by the invasive insect pest – oak lace bug (Corythucha arcuata). In Fagus sylvatica forests damage was caused mainly by abiotic factors (snow and wind), and wood destroying fungus Fomes fomentarius.
The study covers Phase 2 of the ecological-phytogeographic analysis of the dendroflora of Lozenska Mountain. Its purpose is to characterize 15 species-edificators of tree and shrub communities in the mountain and to point out the indicators that most determine the assessment of their ability to long-term adaptability to mountain conditions (convertibility). The performed characterization of the edificators with respect to the reference species shows some heterogeneity in the influence of the factors and the distribution of the groups of species. Indicators, which determinate the most convertibility assessments of edificators are cryoclimatic factor, edaphic regimes and soil pH.
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