The Danube is the second-longest river in Europe that is subjected to various man-made alterations, including those related to hydro-power plants. We surveyed and analyzed the presence and abundance of macrophytes in the main channel from 2582 river kilometers (rkm) to 171 rkm. We also assessed selected habitat parameters in the sampled river stretches. Sixty-eight different plant species were recorded along the entire course. Among neophytes, we found Elodea nuttallii, E. canadensis, Vallisneriaspiralis and Azolla filiculoides. Based on similarity analysis, we distinguished 15 plant communities, most of which were defined as associations, which were classified into 5 alliances and represented three vegetation classes, namely vegetation of rooted hydrophytes Potamogetonetea, the vegetation of pleustophytes Lemnetea and vegetation of marshes Phragmitetea. The number and abundance of plant species, as well as plant communities recorded in single stretches, varied along the course. Canonical correspondence analysis (CCA) revealed that environmental parameters explained 21% of plant species composition. CCA runs with neophytes explained 41% of the variance, and current velocity, water transparency, species number and bank structure were significant variables. The present study revealed that the free-running sections of the river are poor in number and abundance of plant species, whereas impounded reaches mainly show an opposite result.

This study was carried out in the Bucegi Natural Park, a protected area of the Romanian Carpathians. It aims at documenting the potential sensitivity of six widespread Natura 2000 habitat types and of all plants with conservative value (200 taxa) in the mountain area, to the changes in temperature and humidity, predicted for this century. Regional expert knowledge and environmental indicator values were considered in assessing the potential habitat’s sensitivity. The results support the evidence that sensitivity to temperature may be potentially higher for habitats at alpine and subalpine levels (bushes and grasslands) and medium for forest habitats. Sensitivity to moisture was detected as potentially high for forest habitats and as medium for bushes and grasslands at high mountain elevation. Microthermophilic plants have shown a greater share (76-79%) in alpine and subalpine communities, and the hydrophilic plants (86-96%) in forest communities. About 80% of plants of conservation value (microthermophilic or hydrophilic plants) may be potentially sensitive to predicted warming and drought and 44% of them (microthermophilic and hydrophilic plants) to the changes of both parameters. Climate scenarios (2011-2100) and sensitivity maps (Sat – image interpretation with GIS for the whole mountain area) are included.

This chapter deals with several potential effects of climate change, addressed to Natura 2000 habitats from the following categories: woodlands, grasslands, brushwoods, rocky habitats, coastal and dune habitats, surface water habitats, peat bogs and moorlands. For these categories seven impact classes were identified: seasonal impact, sea level rise, hydrology, soil, extreme events, CO₂ concentration, cumulative effects that change the quality of environmental conditions. The chapter provides information and examples regarding the actual and anticipated types of impacts on Natura 2000 habitats and underlines some trends which can be predicted for the future.

The current chapter aims to highlight some of the potential threats that alpine habitats in Bucegi Natural Park might face given the anticipated climate changes, to document the potential prediction of vulnerability of one representative alpine grassland (Natura 2000 code 6150) and to promote the need to reduce the anthropic stress as an element of the adaptive management, in conditions of climate change.

Understanding the drivers of invasive species’ success is essential for predicting and managing their ecological impacts. Symphyotrichum squamatum, a South American species first recorded in Bucharest in 2015, is currently expanding into urban and peri-urban areas of Romania, raising concerns about its invasive potential. This study provides a comprehensive assessment of its invasiveness by integrating species distribution modeling, a reproductive trait analysis, and morpho-structural evaluations. To deepen our understanding, we compare S. squamatum with S. ciliatum, a species already invasive in Romania, to identify shared traits potentially driving their invasiveness. Using R software (version 4.3.0) with bioclimatic variables, we modeled the potential distribution of both species. The reproductive success of S. squamatum was evaluated through germination tests on seeds from distinct Romanian populations, while anatomical analyses revealed adaptations potentially linked to invasiveness. Our findings indicate that S. squamatum shares traits with successful invaders, as highlighted by its comparison with the invasive S. ciliatum. However, its expansion in Romania appears to be constrained by environmental factors, with continentality emerging as a key determinant influencing the distribution of both species. This study highlights the importance of combining ecological modeling with trait-based analyses to assess invasive potential, offering a robust framework for managing alien species.