Ecology of Elodea canadensis Michx. and Elodea nuttallii (Planch.) H. St. John-Insights from National Water Monitoring in Croatia.

Elodea canadensis Michx. (common waterweed) and Elodea nuttallii (Planch.) H. St. John (Nuttall's waterweed), two invasive aquatic plants from North America, have coexisted in European water bodies since the early 20th century. New localities for both species in Croatia continued to be discovered during a study that ran from 2016 to 2023 as a part of the annual implementation of Water Framework Directive monitoring that covered the entire territory of Croatia (786 sampling points in total). Based on these data, the distribution and ecology of both species were analysed. Elodea canadensis was found at 30 sampling points, mostly in rivers, and E. nuttallii at 15 sampling points, mostly in artificial canals. Nearly three-quarters (72.5%) of all elodea sampling points were in the Pannonian Ecoregion. Elodea canadensis was discovered for the first time in the Continental-Dinaric and Mediterranean-Dinaric Subecoregions. To study the ecology of the species, for each sampling point, vegetation relevés were performed and monthly measurements of physico-chemical parameters were collected. The most common accompanying species for both elodeas are presented, and the difference in species assemblages between the sites with E. canadensis and E. nuttallii was confirmed with the ANOSIM test. Furthermore, Indicator Species Analysis revealed eight species characteristic of E. canadensis sites and eleven species characteristic of E. nuttallii sites. Fitting multivariate models (CCA and NPMR) to species abundance revealed the ecological reaction of E. canadensis and E. nuttallii to environmental descriptors. The most strongly contributing environmental descriptors that influence the distribution of both Elodea species are biochemical oxygen demand, electrical conductivity and total phosphorus. In Croatia, the replacement of E. canadensis with E. nuttallii was observed in several water bodies with high nutrient loads.

Diversity, Ecology and Phytogeography of Bryophytes across Temperate Forest Communities-Insight from Mt. Papuk (Croatia, SE Europe).

It has been widely documented that the complex structure of forest ecosystems supports considerable bryophyte species and functional diversity. In this study, we assessed the diversity, distribution and ecological and phytogeographical features of bryophytes across a gradient of temperate forest types on Mt. Papuk. This is the largest and highest mountain in the lowland, Pannonian part of Croatia, with high geological diversity and various temperate forests covering 95% of the mountain. According to the predominant tree species (oak vs. beech), geological bedrock (calcareous vs. siliceous) and soil reaction (alkaline vs. acidic), 21 study plots were classified into four distinct forest types. In all, 184 bryophyte species (35 liverworts and 149 mosses) were recorded. Although the forest types investigated did not differ significantly with respect to species richness, each was characterized by a considerable number of diagnostic bryophyte species. According to our results, one of the main ecological factors determining the variability of the forest bryophyte composition was geological bedrock and the associated soil reaction. Basiphilous forests developed on carbonate bedrock harbored more thermophilous and nitrophilous bryophytes and were characterized by southern-temperate and Mediterranean-Atlantic biogeographic elements. In contrast, acidophilous forests growing on silicate bedrock were characterized by wide-boreal and boreo-arctic-montane elements, i.e., bryophytes indicating cooler habitats and nitrogen-deficient soils. Based on the results, we hypothesized that the main latitudinal biogeographic distinction between southern and northern biogeographic elements is driven more by geological substrate than by the main tree species in forest communities. The present study confirmed previous findings that bryophytes are good and specific habitat indicators and show associations with different forest types, which can help to understand the complexity, ecological microconditions and biogeographic characteristics of forest communities.

Ecological Preferences and Indication Potential of Freshwater Bryophytes-Insights from Croatian Watercourses.

A comprehensive survey of Croatian watercourses covering the whole of the national territory and investigating inherent watercourse heterogeneity was conducted to explore the ecological responses of the most frequent freshwater bryophytes with respect to water chemistry variables and land use within the catchment area. Direct multivariate ordination (CCA) of vegetation data paired with 18 environmental variables revealed that freshwater bryophytes and their assemblages were segregated along the gradients of water chemistry and the proportion of natural and urban area within the catchment. Generalized additive models (GAM) were employed to explore the ecological responses of individual species. The results showed that most of the investigated species preferred natural, clean, well-oxygenated watercourses, with low nutrient and organic matter content, as well as with low electrical conductivity. Species such as Palustriella falcata, Eucladium vertcillatum, Dichodontium flavescens and Jungermannia atrovirens had narrow ecological niches and were restricted to pristine watercourses, while the most frequent and widely distributed species, such as Fontinalis antipyretica, Rhynchostegium riparioides, Cratoneuron filicinum, Fissidens crassipes, Cinclidotus fontinaloides and C. riparius, had a wide ecological tolerance. Riccia fluitans and Leptodyctium riparium had wide ecological ranges, but with optima in hypereutrophic waters with high nutrient and organic content, as well as high electrical conductivity. Furthermore, these two species were frequently associated with a high share of intensive agriculture and a low share of natural land within the catchment.

Environmental Gradients Shaping the Freshwater Bryophyte Communities of Croatia (Western Balkans).

A comprehensive field survey of 527 sites on 293 watercourses across Croatia revealed 76 sites (14.42%) in which bryophytes were the dominant part of the macrophyte vegetation. Using classification and ordination analyses, we obtained five community types segregated across the gradients of several climatic, physiographic and water chemistry parameters. The Didymodon tophaceus-Apopellia endiviifolia and the Berula erecta-Cratoneuron filicinum communities were mostly confined to the clean and basic karstic rivers of the Dinaric Ecoregion under the influence of the Mediterranean climate, with the Didymodon tophaceus-Apopellia endiviifolia community being a tufa-forming community associated with the seasonally dry watercourses of small catchment areas and cascades along the larger karstic rivers, while the Berula erecta-Cratoneuton filicinum community was mostly associated with rivers with larger catchment areas and permanent flow. On the other hand, the Oxyrrhynchium hians-Chiloscyphus pallescens community and the Fissidens pusillus-Veronica beccabunga community were associated with eutrophic water restricted to small rivers of the Pannonian Ecoregion under the influence of the temperate climate and flowing over silicate bedrock. The most represented and widespread in Croatia was the Cinclidotus community, displaying the widest ecological range in the study. It was mostly associated with the relatively clean karstic rivers of large catchment areas belonging to the Dinaric Ecoregion, with the majority of the sites under the influence of a temperate climate with higher precipitation during the warm period of the year. The geographical patterns of the freshwater bryophyte communities showed that the relatively clean, fast and cold karstic rivers belonging to the Dinaric Ecoregion provide habitats that harbour a greater diversity of bryophyte communities than the watercourses of the Pannonian Ecoregion, where bryophyte-dominated communities are restricted to a small number of small lowland and semi-montane rivers and predominantly occupy periodically flooded microhabitats such as river margins.

Green Christmas: bryophytes as ornamentals in Croatian traditional nativity scenes.

BACKGROUND: The bryophytes are a plant group that is smaller than and not as well known as the vascular plants. They are less used and are almost completely neglected in ethnobotanical studies. Traditional nativity scenes depicting the birth of Christ are commonly decorated with both vascular plants and bryophytes. The aim of this study was to document the diversity of decorative bryophytes sold during the Advent season at farmers' markets in Croatia (Southeastern Europe, Balkan Peninsula). METHODS: Twenty-eight farmers' markets in the two largest Croatian cities (Zagreb in the continental part and Split in the Mediterranean part) were studied in the search for local vendors selling bryophytes during the pre-Christmas season. The bryophytes collected were identified and analysed with respect to families, growth type, life forms and threat status. RESULTS: Among 275 collected specimens, 43 moss and four liverwort species were identified. The mean number of species per vendor was 3.5. The most frequent species were Hypnum cupressiforme, Homalothecium sericeum and Ctenidium molluscum. Mats, wefts and tufts were the most common life-forms, while pleurocarpous prevailed over acrocarpous mosses, as they are usually pinnately branched and form large carpets, suitable for decorations. The overall selection of bryophytes and the decorations made of them were more diverse and abundant in inland Croatia, where 49 vendors at 15 farmers' markets sold goods containing 43 species. In Mediterranean Croatia, at six farmers' markets only 29 vendors sold goods, which contained 18 species. A considerable number of species that are less attractive to harvesters were collected non-intentionally, entangled in carpets of other, more frequent species. Among them, Rhodobryum ontariense and Loeskeobryum brevirostre are rare and insufficiently recorded in Croatia so far. CONCLUSIONS: The present study provided a first perspective on the use of bryophytes in traditional nativity scenes in Croatia and Southeastern Europe, contributing to scarce ethnobotanical documentation of the decorative use of bryophytes in Christmas festivities in Europe and globally.

Croatian freshwater bryoflora-diversity and distribution.

An extensive macrophyte field survey of running and standing waters was conducted from 2016 to 2021 at 786 sampling sites across Croatia as a part of the implementation of the Water Framework Directive. This survey is the first to present a comprehensive floristic catalogue of the freshwater bryoflora, along with an analysis of the distribution and diversity patterns on a national level. In all, 83 bryophyte species (68 mosses and 15 liverworts) were recorded in the 228 sites, with average species richness of 4.17 species per site. The most frequent species were Fontinalisantipyretica, Rhynchostegiumriparioides, Leptodictyumriparium and Cratoneuronfilicinum. The majority of the species encountered were rarely found, with over 70% of species recorded on less than 10 sampling sites and the majority of the species not being truly aquatic, rather being classified as facultative aquatics. The Dinaric Ecoregion, characterised by clean, cold, fast-flowing karstic rivers, especially in the Continental Subecoregion, supported higher freshwater bryophyte diversity than the lowland Pannonian Ecoregion, with mostly slow, eutrophic lowland watercourses with unstable sandy and gravelly alluvial sediments. Chorological comparison of Croatian eco- and subecoregions revealed the expected dominance of circumpolar and European elements, i.e. temperate chorotypes, as well as some biogeographical differences. The most frequent life forms were aquatic trailings and turfs. Amongst the recorded species, perennials and colonists were the most represented life strategies. The analysis of both the life-form and life-strategy spectra showed some differences amongst the Croatian regions, supporting the fact that the Dinaric Ecoregion provides more truly aquatic habitats and microhabitats suitable for the freshwater bryophytes, while in the Pannonian Ecoregion freshwater bryophytes dominantly inhabit the periodically submerged riparian zones, for example shaded lowland forest streams and rivulets or gently sloping margins of rivers and lakes.