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Abstract The presence, abundance, and distribution of aquatic macrophytes and their growth forms in the river Krka in Slovenia were studied. The studied slow‐flowing lowland River Krka is also called a »green river« since it is overgrown with macrophytes from its source to its outflow to the river Sava. The environmental parameters of the river ecosystem were also assessed using the modified version of the RCE (Riparian, Channel, and Environmental Inventory) method. Within 24 sections reaching from 100 to 250 m, 23 taxa of macrophytes were found. Sections were distributed noncontinuously from the source to the outflow more or less equally along the river course. The invasive alien species Elodea canadensis reached the highest relative abundance, followed by Ranunculus trichophyllus, Potamogeton crispus, Myriophyllum spicatum, Ceratophyllum demersum, and Potamogeton nodosus. Potamogeton crispus was present in most of the studied sections followed by Nasturtium officinale and M. spicatum. The river offers suitable conditions for the high diversity of macrophytes regarding the type of substrate, low flow velocity, heterogeneity of habitats, and relatively high concentrations of nutrients. In comparison to the survey performed in 2003, when the river Krka was surveyed continuously from the source to the outflow, we found that seven of the submerged and natant macrophytes were not detected in 2020. Macrophytes, growing in the river Krka, indicated meso‐ to eutrophic conditions. Five species recorded in the river Krka are listed on the Red list of endangered species in Slovenia, indicating the need to conserve the river ecosystem.

Ponds are important habitats for aquatic plants and other biota, particularly in regions where the quality of aquatic ecosystems is deteriorating or even disappearing. Ponds provide refuge for many species and serve as foraging places for others. The ponds studied are located in the Brdo Estate and are under special protection to maintain their educational and other ecosystem services. This study examined the temporal differences (20 years) of the plant communities in eleven ponds concerning eutrophication and/or other human pressures. Various measurements were taken between the two surveys to improve the quality of inflowing water. The selected ponds’ physical and chemical parameters, water depth, and transparency were measured. According to our results, water transparency and temperature significantly shaped the structure of the plant community and significantly influenced the presence and abundance of aquatic plants. The changes were reflected in the disappearance of four species of the genus Potamogeton, namely P. filiformis, P. lucens, P. pectinatus, and P. trichoides, which were recorded in 2001 but not in 2021. Secondly, the average number of plant species in the ponds has slightly increased in 20 years, mainly due to emergent plants. The construction of wastewater treatment plants in the catchment area prevented the eutrophication processes.

The diversity of macrophytes and macroinvertebrates in small standing waters of different origins and characteristics was investigated. This survey covered 19 ponds in the Drava field in northeastern Slovenia. The influence of the macrophytes on the macroinvertebrates was investigated and the main environmental factors that had the most significant influence on the composition of the two communities were identified. Sixty-seven taxa of macrophytes and seventy-three families of macroinvertebrates were identified. We found that a diverse macrophyte community has a positive effect on the macroinvertebrate community. In contrast, the dominance of a single macrophyte species has a strong negative influence on the richness of the macroinvertebrate community. The taxonomic richness and abundance of the macroinvertebrate community in the natural ponds was statistically significantly higher than that in artificial ponds. The significant differences in the environmental characteristics between the natural and artificial ponds, such as the macrophyte cover, conductivity, and riparian zone width, may account for these differences. Our study suggests that a greater diversity of macrophyte and macroinvertebrate communities in natural ponds is enabled by abundant but diverse macrophyte cover, low phosphorus content, and wide riparian zones, which require appropriate management of ponds and their catchments.

In alpine Lake Bohinj, which is an LTER site and a part of the national park, the occurrence and depth distribution of submerged and emerged aquatic macrophytes were analyzed. Nine submerged and one emergent macrophyte taxa were found in the lake: Myriophyllum spicatum, Chara virgata, Chara aspera, Potamogeton lucens, Potamogeton alpinus, Potamogeton crispus, Potamogeton perfoliatus, Potamogeton pusillus, Ranunculus circinatus with the synonym Batrachium foeniculaceum and the emergent species Phragmites australis. The depth of the vegetation zones was measured using a depth meter and their coordinates were recorded using a GNSS antenna with RTK receiver. These data were used along with a DEM of lake depths to accurately map the potential zone of macrophyte growth, which was based on the depths of macrophyte distribution. The potential zone of macrophyte growth consisted of 28 different transects and covered 240.14 ha of the lake. The macrophytes covered 5.55 ha. The most common and abundant species was M. spicatum. A significant difference in macrophyte cover was found between the south and north shores of the lake, with the south shore having more patches with a larger total area. A clear difference in macrophyte cover was also noted between the main inflow and outflow of the lake. The presence of macrophytes and their diversity varied in different parts of the lake due to differences in slope, depth and type of substrates.

Inland wetlands are one of the most vulnerable ecosystems on Earth and have one of the highest rates of decline in surface and biodiversity [...]

The structure of phytobenthic diatom communities was studied to reveal differences between natural and channelized river sections in Slovenia. As part of the national monitoring of surface waters, samples of phytobenthos were collected at 85 sites throughout the country according to standard protocols. At the same time, basic environmental parameters were also assessed. Trophic (TI) and saprobic (SI) indices were calculated based on diatoms and other algae, while diversity indices and gradient analyses were performed only for the diatom community. The results showed that channelized rivers harbor significantly more diverse benthic diatom communities than natural sections, mainly due to the significantly higher number of motile diatom taxa that are able to take advantage of more nutrient-rich and less-shaded river sections because of their high adaptability. Selected environmental parameters explained 34% of the variability in diatom community structure when taxa were classified into ecological types. The removal of Achnanthidium minutissimum yielded clearer results (24.1%) than the total species matrix (22.6%). Therefore, we suggest excluding this taxon from calculations of TI, SI, or other indices when it is determined as A. minutissimum complex, because A. minutissimum complex was most abundant in both types of reaches in our study and has a wide ecological amplitude, which reduces the indicative power of the diatom community in the evaluation of environmental conditions and ecological status.

Metals stored in sediments of lakes can bioaccumulate through the food chain, posing a risk to the environment and human health. Alpine lakes are supposed to be less affected by pollution than lowland lakes and are vulnerable to any changes and impacts in their catchment areas because of their remote position and ultra-oligotrophic character. Therefore, we used a model Alpine lake, Bohinj (in the Triglav National Park, Julian Alps, Slovenia), to evaluate the load of metals in the abiotic and biotic compartments of the ecosystem, in order to assess the spatial distribution of metals, and finally, to determine whether past and present human activities in the lake’s catchment area may be causing pollution. To this aim, the contents of Cu, Pb, Cr, Cd, Co, Mn, Fe, Zn, Hg and Ni in the sediment, water, and macrophyte samples were determined. The results showed that the average content of some toxic elements, especially in the sediments (Cd 0.52 mg/kg; Hg 0.03 mg/kg) and plants (Co 0.71 mg/kg; Cr 5.88 mg/kg) was elevated compared to natural background values. High Hg contents could be connected with natural geological sources, while other elements were probably of anthropogenic origin. High levels of all elements in the eastern part of the lake indicated long-term pollution, which could be a consequence of past iron extraction and military activities in the vicinity. On the other hand, high contents of elements in the water suggests that intensive touristic activities in the area may cause temporal pollution in the summer. The study sheds light on complicated processes governing the distribution of trace metals in Alpine lakes.

This contribution discusses the use of field measurements and remotely sensed data in an exploration of the effects of environmental parameters on the riparian and littoral stands of the common reed (Phragmites australis) in an intermittent wetland in Slovenia. For this purpose, we created a normalized difference vegetation index (NDVI) time series extending from 2017 to 2021. Data were collected and fitted to a unimodal growth model, from which we determined three different stages relating to the reed’s growth. The field data consisted of the above-ground biomass harvested at the end of the vegetation season. Maximal NDVI values at the peak of the growing season exhibited no useful relationship with the above-ground biomass at the end of the season. Intense and long-lasting floods, especially during the period of intense culm growth, hindered the production of common reeds, while dry periods and temperatures were helpful before reed growth began. Summer droughts exhibited little effect. Water level fluctuations exerted a greater effect on reeds at the littoral site due to more pronounced extremes. In contrast, more constant and moderate conditions at the riparian site benefited the growth and productivity of the common reed. These results can prove useful for decision making regarding common reed management at the intermittent lake Cerknica.

The contribution discusses macrophyte communities in natural and man-made waterbodies located on the active floodplain along the Drava river (Slovenia). We presumed that these different types of wetlands host a great number of macrophyte species, but this diversity may be affected by the presence of alien invasive species Elodea canadensis and E. nuttallii. Presence, relative abundance, and growth forms of plant species along with selected environmental parameters were monitored. Correlation analyses and direct gradient analyses were performed to reveal the possible relations between the structure of macrophyte community and environmental parameters. Number of macrophytes in surveyed water bodies varied from 1 to 23. Besides numerous native species we also recorded Elodea canadensis and E. nuttallii, which were present in 19 out of 32 sample sites, with E. nuttallii prevailing. The less invasive E. canadensis was absent from ponds and oxbow lakes but relatively abundant in side-channels, while E. nuttallii was present in all types but dominant in ponds. The most abundant native species were Myriophyllum spicatum and M. verticillatum, Ceratophyllum demersum and Potamogeton natans. Correlation analyses showed no negative effect of the invasive alien Elodea species to the species richness and diversity of native flora. Positive correlation between the abundance of E. nuttallii and temperature of the water was obtained.

The aim of this study was to reveal the changes of macrophyte community over time and along the course of the Ižica River. In 1996, 2000, and 2016, we surveyed the distribution and abundance of macrophyte species in the lowland Ižica River, which originates in the town of Ig and then flows through an agricultural landscape. We calculated the River Macrophyte Index (RMI), which reflects the ecological status of the river. In 2016, ecomorphological conditions of the river, using the Riparian, Channel and Environmental inventory, were also assessed. In just 10.5 km of the river, we identified 27 taxa of macrophytes, among which Potamogeton natans, Sagittaria sagittifolia, and P. perfoliatus were the most abundant. Detrended correspondence analysis showed that, in 1996, the surveyed stretches differed more according to macrophyte composition than in the following years. The assessed environmental parameters explained 43% of the variability of the macrophyte species; riverbank stability explained 20%, riverbed structure 10%, while vegetation type of the riparian zone and bottom type explained 7 and 5%, respectively. The species composition of the macrophyte community revealed significant changes over the years of the riverine ecosystem. Comparison of RMIs in 1996 revealed better conditions in the upper and middle part of the river, while in 2016, the situation was the opposite, since the conditions in the upper part deteriorated significantly over time, while the lower part of the river had the best ecological status. These changes may be due to a considerable increase in the population of the settlement Ig, while better status in the lower course of the river may be a consequence of improvements in the infrastructure and the use of sustainable agricultural practices in the catchment due to the establishment of a formal area of protection.

Water is not only the essence of life and medium of organisms but also the environmental factor that shapes biocenoses, including plant communities [...]

The aim of this research was to investigate the structure of the benthic diatom community and its relations to selected environmental parameters. We collected samples in 16 karst ponds in the alpine region of Slovenia, where the Alpine karst is found. Since the predominating substrate in these ponds was clay, the epipelic community was analyzed. Hydromorphological characteristics, and physical and chemical conditions were also measured at each site. We found 105 species of diatoms, which belonged to 32 genera. The most frequent taxa were Gomphonema parvulum (Kützing) Kützing, Navicula cryptocephala Kützing, Sellaphora pupula (Kützing) Mereschkowsky (species group) and Achnanthidium pyrenaicum (Hustedt) Kobayasi. The pond with the lowest diversity was found at the highest altitude, while, on the other hand, the most species-rich pond was found at the lowest altitude. Regarding the ecological types, the most common were motile species. We confirmed a positive correlation between the number of diatom species and the saturation of water with oxygen, while correlation between species richness and NH4-N was negative. The content of NO3-N and NH4-N explained almost 20% of the total variability of diatom community. Unlike our expectations, we calculated a negative correlation between the diversity of macroinvertebrates and diatoms, which is probably a consequence of different responses to environmental conditions.

The present research aimed to determine the diversity of macrophyte taxa in the Ljubljanica River and its relationship with environmental parameters. In each of the 19 river sections, the presence and abundance of plant taxa were recorded, and basic physical and chemical parameters were measured. Additionally, selected environmental parameters were assessed using a modified version of the Riparian, Channel and Environmental (RCE) method. We compared the obtained data set with survey data from the year 2004. In 2019, a total of 34 macrophyte taxa were recorded. The dominant taxa with the highest abundance were Sparganium emersum, Callitriche sp., and the invasive alien species Elodea canadensis. The species richness and diversity of macrophytes decreased with distance from the source, an increase in pH, and alterations of the riverbed structure due to interference in the riverine ecosystem in the lower part of the Ljubljanica River and its catchment. The comparison of 2004 and 2019 surveys revealed a decrease in the overall presence and abundance of P. natans and in the frequency of occurrence of the species Myriophyllum spicatum and an increase in the presence and abundance of the invasive alien species Elodea canadensis.

Rivers and streams are heterogenous ecosystems that host a great number of vascular plant communities. The territory of Slovenia is highly diverse regarding geomorphologic, geologic, climatic, and edaphic conditions. We presumed that environmental variability will also affect the distribution of hygrophilous vascular plants in running waters and consequently the structure of plant communities they form. We analyzed macrophyte, spatial, and environmental parameters in 906 stretches of the watercourses occurring in the Dinaric, Pannonian, and Po lowland hydro-ecoregions. We determined 87 vascular plant taxa. The most abundant were Myriophyllum spicatum, Phalaris arundinacea, and Potamogeton nodosus. Submerged macrophytes presented about one third of total species abundance, while amphiphytes were somewhat less abundant. Canonical correspondence analysis (CCA) revealed that distance from the source explained 15.1% of the growth form type variability, and current velocity and latitude explained 4.1% each. With the assessed parameters, we explained 31.6% of the variability. When CCA was run with taxa, only 20.9% of their variability was explained with statistically significant parameters. We distinguished 25 different plant associations belonging to five classes and nine alliances. The majority of defined plant communities were distributed in different watercourses belonging to different hydro-ecoregions. Only seven communities had a narrower distribution range, three of them on karst poljes. Among them, the new association Mentho aquaticae-Oenanthetum fistulosae from the river Mali Obrh on the Loško polje was described in this contribution.

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.

The article deals with wet meadow plant communities of the alliance Trifolion pallidi that appear on the periodically inundated or waterlogged sites on the riverside terraces or gentle slopes along watercourses. These plant communities are often endangered by inappropriate hydrological interventions or management practices. All available vegetation plots representing this vegetation type were collected, organized in a database, and numerically elaborated. This vegetation type appears in the southeastern part of the Pannonian Plain, which is still under the influence of the Mediterranean climate; its southern border is formed by southern outcrops of the Pannonian Plain and its northern border coincides with the influence of the Mediterranean climate (line Slavonsko Gorje-Fruška Gora-Vršačke Planine). Numerical analysis established four plant associations—Trifolio pallidi–Alopecuretum pratensis, Ventenato dubii–Trifolietum pallidi, Ranunculo strigulosi–Alopecuretum pratensis, and Ornithogalo pyramidale–Trifolietum pallidi. Each association was elaborated in detail: diagnostic plant species, nomenclature, geographical distribution, climatic and ecological conditions, and possible division into subassociations. Results are presented in a distribution map, figures resulting from numerical analysis, and a synoptic table. The hydrological gradient was found as the most important factor shaping the studied plant communities. The article also brings new field data on this vegetation type, which has not been sampled for decades and is in process of evaluation to be included as a special habitat type in the Habitat Directive.

The aim of the research was to investigate the influence of environmental factors on the structure of epilithic diatom communities in the Sava River from the source to the state border 220 km downstream. The river had numerous human influences along its course, such as municipal and industrial wastewater, agriculture, hydroelectric power plants, etc. The main objective of the research was to find out the influence of human pressure on the structure of the epilithic diatom community under winter and summer conditions. Winter and summer samples were taken at nine sites. At each sampling site, a set of abiotic factors was measured and another set of environmental parameters was evaluated. The analyses showed that nitrogen and phosphorus concentrations increased downstream. We identified 118 different species of diatoms. The most common taxa were Achnanthidium minutissimum and A. pyrenaicum. Planktonic species Cyclotella meneghiniana was only found in the samples of the lower part of the Sava, which is unusual for the epilithic community. The composition of the epilithic diatom community was significantly influenced by conductivity and water temperature, pH and distance from the source. The similarity between diatom communities closer to the source of the river was higher than between communities from the lower part of the Sava River. The values of the trophic and saprobic indices increased downstream and showed that the pollution of the river with nutrients and organic matter increases with the distance from the source. Both indices were significantly higher in winter and showed a more impaired river ecosystem during the winter.

Hydromorphological alterations influence a wide range of environmental conditions as well as riparian vegetation and the structure of the macroinvertebrate community. We studied relationships between the structure and diversity of the macroinvertebrate community and hydromorphological and other environmental conditions in the river Gradaščica (central Slovenia). The Gradaščica river is a pre-Alpine torrential river that has been morphologically altered by humans. A selection of abiotic factors was measured, the ecomorphological status of the river was assessed, vegetation in the riparian zone was surveyed and benthic macroinvertebrates were sampled. Correlations between diversity and the structure of the macroinvertebrate community, environmental parameters and occurrence of invasive alien plant species in the riparian zone were identified. The significance of the influence of environmental parameters on the structure of the macroinvertebrate community was examined. We found that hydromorphological alterations in the river have had a significant influence on the diversity and composition of the macroinvertebrate community because of changes of flow velocity and the spread of invasive alien plant species that has followed those changes. Factors that also significantly influence the composition of macroinvertebrate community are distance from the source and conductivity. Our findings suggest minimization of further human hydromorphological changes of watercourses could prevent the loss of biodiversity of riverine ecosystems.

Lake Cerknica is an intermittent wetland ecosystem with extreme water level fluctuations. It hosts extensive reed stands that have colonized different habitat types. Two different stands were compared: a lake stand not directly influenced by the intermittent River Stržen and a riparian stand near River Stržen. Reed productivity (growth and assimilate allocation) was monitored for these reed stand types over 13 years (2007–2019), and this measurement was compared to monthly water levels and air temperatures. Reeds from the lake reed stand were significantly shorter with a lower shoot density, overall biomass production, and ratio of flowering plants. A correlation analysis revealed stronger and more numerous significant correlations between environmental and reed productivity parameters for the lake reed stand compared to the riparian reed stand. The variabilities of the growth and assimilate allocation parameters in the lake reed stand were both mostly explained by the combined water levels for June and July, which explained 47% and 52% of the variability, respectively. The most influential temperatures were in May, which explained 29% and 19% of the variability of growth and assimilate allocation parameters, respectively. For the riparian reed stand, water levels and temperatures out of the vegetation season appeared more important. Therefore, habitats with permanent water are more suitable for reeds than those with fluctuating water. However, fluctuating water conditions are expected to become more common due to climate change.

We investigated the presence and abundance of invasive alien plant species (IAS) in the riparian zones of rivers in relation to different environmental parameters. We surveyed the spatial and human-influenced characteristics of the riparian zones, river channels, and land use along seven Slovenian rivers. We further monitored the presence and abundance of IAS with different natural properties and different human impacts to define the characteristics of non-infected and heavily infected reaches. Special attention was given to different life forms of IAS. The presence and abundance of IAS positively correlated with distance from river source, current velocity, and water depth, and negatively correlated with altitude, naturalness of the land use, width and completeness of the riparian zone, height and structure of its vegetation, and condition of the riverbed and banks. Annuals prevailed among IAS at 48%, with 37% herbaceous perennials and 15% woody species. The vine Echinocystis lobata was the most abundant IAS, which was found in 179 out of the 414 river reaches analysed, followed by the annual Impatiens glandulifera and the herbaceous perennial Solidago gigantea. E. lobata was spread over the native riparian vegetation and was affected by the natural gradients of the rivers in terms of altitude and distance from the river’s source. Reaches without IAS significantly differed from reaches colonised with IAS in the width of riparian zone, vegetation height and structure, land-use next to the river, and distance from the source. As IAS in riparian zones affect riparian and aquatic communities, there is the need for management practices to maintain and establish complex riparian zones that are resistant to IAS colonisation.

The catchment area in urban and agricultural landscapes is greatly influenced by human activities that reflect also in physical and chemical characteristics of water as well as in species diversity in water bodies. The diversity and the species composition of epilithic diatom communities in the Savinja River, as well as basic environmental parameters were analysed. Sampling sites were selected in reaches subjected to different influences from the catchment area and with different physical and chemical characteristics. Samples were collected at the site where the Savinja River enters the urban area of the town Celje, at the end of urban landscape and downstream of the Celje waste water treatment plant outflow. The most common and dominant diatom species in the periphyton community was Achnanthes biasolettiana. Other common diatom taxa that were found in all samples and at least in one sample exceeded relative abundance of 10% were Nitzschia fonticola, Amphora pediculus and Nitzschia dissipata. The results of the redundancy analyses (RDA) revealed that the variance of the epilithic diatom community was explained by O2 saturation(35%) and saprobic index (33% of TVE). Diatom species richness was positively correlated with O2 saturation. Shannon-Wienerdiversity index was positively correlated with saprobic index values based on all algae and trophic index calculated on the base of diatoms indicating a relatively low organic matter and nutrient input into the river system. The results showed that no significant changes in epilithic diatom species composition and no negative impacts on diversity of epilithic diatom community in the Savinja River were detected on its flow through the urban landscape. Moreover, changes between the seasons were more evident than changes between sampling sites, confirming the importance of sampling date for monitoring.

The vines Echinocystis lobata and Parthenocissus quinquefolia are spreading over the natural vegetation in riparian zones, which may significantly affect riparian vegetation properties and the quality of litter for aquatic organisms. We examined leaf morphological, biochemical and optical traits of these invasive alien species, each paired with its host, the willows Salix caprea and S. fragilis, respectively. The vines altered the host radiation environment and the amount of photosynthetic pigments. Both vines had significantly higher specific leaf area and lower leaf tissue density compared to the willows, even though the leaves of P. quinquefolia were significantly thicker. Leaf optical properties varied significantly between vines and willows in some spectral regions. Compared to the willows, the vines reflected less light as UV, and more as green, and transmitted more light as green, yellow and red. The overgrowth of the willows with vines affected the reflectance of the willow leaves. Redundancy analysis of the relationships between leaf biochemical traits and reflectance spectra showed that chlorophyll a, anthocyanins, and UVB- and UVA-absorbing substances explained 45% of the reflectance spectra variability, while analysis with morphological traits revealed that specific leaf area, leaf thickness and upper cuticle thickness explained 43%. For leaf transmittance, UVB- and UVA-absorbing substances, carotenoids and anthocyanins explained 53% of the transmittance spectra variability, while analysis with morphological traits revealed that specific leaf area explained 51%. These data show that invasive alien vines can be discerned from each other and their hosts by their spectral signatures. In addition, the differences in the leaf functional traits between the vines and their hosts indicate significant differences in the quality of the plant litter entering the river.

Invasive alien plants present a threat to diversity of native species. An attempt to evaluation of potential endangerment of specific habitats due to the presence of invasive alien plant species was made and results are presented in this paper. Data about the presence of invasive alien plants in specific habitats were extracted from the database Flora of Slovenia (at the Centre for Cartography of Fauna and Flora). The list of the most frequent invasive alien plant taxa in natural and semi-natural habitats is presented as well as the lists of invasive alien plants with potentially most negative influence on the biodiversity in different habitats. In general, taxa with potentially most negative influence on the biodiversity of natural habitats in Slovenia are: Robinia pseudacacia, Solidago gigantea, Fallopia japonica and F. × bohemica, Rudbeckia laciniata,Helianthus tuberosus. In the dataset the highest number of data about presence of invasive alien plants referred to riparian zones (44%). Thesecond highly infected group of habitats was floodplain woods. According to the Ellenberg indicator values the most of the invasive alien plants prefer nutrient-rich and sunny sites. The negative effect of Fallopia × bohemica on light conditions in established stands andconsequently on the species richness of native plants was also detected.

The paper presents wet meadow vegetation with taxon Molinia caerulea (L.) Moench subsp. caerulea in Slovenia. The main objective of this study was to examine the plant species composition and plant species richness of wet meadow plant communities with the mentioned dominating or co-dominating plant taxon. Vegetation was recorded in accordance with standard Central European method. Vegetation types were classified by means of multivariate analysis. Four associations from the alliance Molinon Koch 1926 were identified and analysed: Plantagini altissimae-Molinietum caeruleae Marchiori & Sburlino 1982, Selino-Molinietum caeruleae Kuhn 1937, Carici davallianae-Molinietum caeruleae Špániková 1978 and Junco-Molinietum caeruleae Preising 1951 ex Klapp 1954. Ecological characteristics, plant species composition and richness of the delimited plant communities are presented, as well as their syntaxonomic position and distribution. For two of the mentioned communities relevés made in Slovenia are published here for the first time.

During the investigations of wetlands in Slovenia over the last decade specific plant communities in spring fens were found. Stands with species Eleocharis quinqueflora occurring in depressions inundated with standing and/or running water were found in the Alpine, pre-Alpine and Dinaric phytogeographic regions of Slovenia. Standard Central European method for vegetation research was used and multivariate analyses were performed using Syn-Tax program. Stands were classified in two different species-poor, small-scale plant communities, most of them into associationEleocharitetum pauciflorae Lüdi 1921. This rare plant community occurs in the Alpine and Carpathian regions and in northern Europe and has not been recorded in Slovenia before. The association Eleocharitetum pauciflorae is a two-layered plant community of calcium-rich fens. It thrives in shallow temporary paddies and on the sandy or stony slopes with seeping water. Smaller group of relevés was classified into association Scorpidio-Utricularietumminoris Ilschner ex T.Müller et Görs 1960. This association thrives in permanent paddies, where the water is deeper as in a case of the first association. Since the dominating species Eleocharis quinqueflora and Utricularia minor, respectively, have the status of a vulnerable species according to Red List of Slovenia, the stands of the studied communities, which represent vital populations, should be preserved as well as the corresponding habitat types.