Abstract A revision of the Taraxacum section Erythrosperma in the Republic of Moldova, based on fieldwork and the study of herbarium specimens, has revealed two new species, T. parnassicum and T. persicum , for the country’s flora, confirmation of the occurrence of the sexually reproducing species T. erythrospermum s. str., and records of plants belonging to the T. scanicum group, previously never reliably documented in the Republic of Moldova. These findings are supplemented or supported by descriptions of the species and their distribution, photographs of herbarium specimens, and chromosome numbers and ploidy information. The chromosome number of T. persicum , 2n = 24, is reported here for the first time. An identification key to T. sect . Erythrosperma in Republic of Moldova, compiled based on the newly collected material, is presented.

In the valley of Espot in the central Iberian Pyrenees, two species of juniper, Juniperus communis and J. sabina, co-occur in the same habitats, showing a similar encroaching ability as prostrate shrubs expanding on former rangeland. Outside of this valley, however, J. communis is widespread from the regional to the Holarctic level whereas J. sabina is only sparsely found in mutually distant Palaearctic regions, where it remains restricted to scarce locations. We set out to analyse the dynamics of both species as drivers of landscape transformation and to unveil which differences may explain their contrasting biogeographic performance. To do so, we analysed them in terms of plant traits, phenology, primary growth, population structure and their role in the landscape, all along an elevation gradient. Juniperus communis and J. sabina showed similar strong investment into stress resistance, according to the functional traits measured (SLA, LDMC, leaf lifespan), and both species expanded laterally at similarly noticeable ratios. Along the elevation gradient, we found shifts in functional traits and performance that respond to environmental differences. The populations of J. communis included more balanced age classes and showed good recruiting ability. By contrast, J. sabina exhibited a poor recruiting ability, with populations lacking juveniles and including notably old shrubs. The longevity and clonal performance of this species would explain its persistence only in particular locations scattered over distant regions. Therefore, the contrasting plant distribution and ecology of the two species (i.e. a widespread and active colonizer vs a relict growing in secluded locations) appears to be based on a few interspecific developmental and reproductive differences.

Invasive clonal species may exhibit different growth strategies than their native clonal competitors. In this study, we examined the spatial distribution of tiller outgrowth and the bud bank by comparing the investment in phalanx versus guerilla growth of a native and invasive perennial grass in North America. We also examined the effect of altered precipitation frequency, clipping, and competition on their clonal growth strategies. Investment in phalanx and guerilla growth was assessed by examining live propagule and tiller production from the plant crown versus its rhizomes. Although invasive Bromus inermis and native Pascopyrum smithii exhibited similar clonal growth strategies as young seedlings, their clonal growth strategies significantly differed by the end of their first growing season. Pascopyrum smithii invested in dual phalanx and guerilla tiller outgrowth and bud placement, and B. inermis primarily invested in phalanx tiller outgrowth and bud placement. Competition rather than intra-annual precipitation variability and clipping altered the clonal growth strategy of these species. Intra- and inter- specific competition did not alter tiller outgrowth for either species. However, inter-specific competition caused both species to alter their bud placement. Bromus inermis shifted more buds from phalanx to guerilla positions while P. smithii shifted in the opposite direction. This may enable invasive B. inermis to expand while confining native P. smithii to more localized areas in the future. Clonal growth strategies appear to be species specific and responsive to inter-specific competition. Investigating the belowground bud aspect of clonal growth can reveal the mechanism driving the future aboveground clonal growth strategy of native and invasive rhizomatous grasses and help inform the patterns of invasion within a plant community.

Most hemiparasitic plants are generalists with a broad host range, but they grow better in the presence of some plant species than with others. In mixed communities of hosts, hemiparasites prefer some hosts over others, but it is not yet known if hemiparasite roots can distinguish between the roots of different plant species and show directed growth (host tropism). We performed host choice experiments, exposing seedlings of Rhinanthus alectorolophus in agar plates simultaneously to seedlings of grass and legume species known to be hosts of good or poor quality for the parasite, and measured directed root growth and haustoria formation. Parasite roots did not show directed growth towards the roots of a good compared to a poor host species within a host functional group. However, parasite roots grew more strongly in the direction of legume than grass roots. The probability to form haustoria with host roots did not differ between host species, and microscopy revealed that functional haustoria were formed even with a very poor host, the grass Anthoxanthum odoratum. Our results show that growth experiments in agar plates are a suitable approach to study early host choice of hemiparasites. Our finding that hemiparasites can (initially) form functional haustoria even with very poor hosts emphasizes that the quality of a plant species as a host depends on several independent processes, including early host recognition, haustoria formation, resource supply and competition.

The Carex flava aggregate belongs to one of the most taxonomically difficult groups of sedges which colonize diverse habitats, from organic to sandy, from acidic to alkaline, usually humid and moist. The study included 129 vegetation plots and ten soil variables (organic matter, phosphorus, potassium, magnesium, calcium, carbonates, carbon, nitrogen, pH, and the ratio between organic carbon and nitrogen). The main aim was to determine the relationships between the various plant communities C. flava agg. occur in and their soil properties. With the aid of the two-way indicator species analysis and cluster analysis, we delimited nine vegetation types from the Scheuchzerio palustris-Caricetea fuscae, Littorelletea uniflorae, Molinio-Arrhenatheretea and Alnetea glutinosae classes differing in their response to soil properties. The CCA revealed pH, N, K, C, CaCO3, P and Ca to be statistically significant, and to account for 11.55% of the total variance in species composition. The largest differences, both in terms of species composition and in soil conditions, were revealed between communities with C. lepidocarpa and C. demissa. Carex lepidocarpa occurred in calcareous and extremely rich fens (Caricion davallianae) whereas C. demissa was found to occur in poor and moderately rich fens (Sphagno-Caricion canescentis, Caricion canescenti-nigrae). Carex flava grew mostly in calcareous, rich fens and wet grasslands (Caricion davallianae, Calthion palustris). Carex viridula was found in both calcareous, extremely and moderately rich fens and wet grasslands, and in nutrient-poor habitats such as dunes and sandy lake shores. The ecological niche of C. viridula is very wide and this species showed no affinity to any specific syntaxon.

Keystone plant species are known to provide various essential ecosystem services. The Mediterranean keystone species Stipa tenacissima improves soil functioning and facilitates the establishment of different plant species, so it is used in restoration programmes. In this paper, we aimed to predict the impacts of climate (aridity) and soil texture (sand content) on the establishment and development of S. tenacissima (number, cover and width of tussocks) and on soil properties underneath S. tenacissima tussocks. This research demonstrated a significant positive effect of S. tenacissima on LFA (landscape function analysis) indices, revealing the importance of this key species in the soil stabilization, water infiltration and nutrient cycling. Similarly, soil nutrient contents (organic carbon and total nitrogen) and enzyme activities (s-glucosidase and phosphatase) were highly improved underneath S. tenacissima compared to bare ground areas. However, increases of aridity and sand content showed strong negative effects on soil organic carbon, total nitrogen and activities of the hydrolytic enzymes both on bare ground areas and underneath S. tenacissima tussocks. Furthermore, we found that the climate is the main controller of the number of S. tenacissima tussocks, cover and width. Soil sand content influences the colonization of S. tenacissima, as it affects soil water potentials. In general, this study demonstrates the non-sustainability of S. tenacissima under a warmer and drier climate, which will negatively affect its ability to create islands of fertility in South Mediterranean grasslands.

River gravel-bar habitats are highly endangered. They are still well-preserved in the Caucasus, but developing conservation strategies is burdened by the lack of data from this region. We studied vegetation and habitat types on gravel bars of 22 rivers in Georgia, including successional stages from open early-successional herbaceous vegetation to scrub. We distinguished five vegetation types based on vegetation physiognomy and β-flexible clustering of species composition, and described them as phytosociological vegetation units: Early-successional herbaceous vegetation at higher elevations was described as the new association Epilobietum colchici and that at lower elevations as the Petrorhagia saxifraga–Crepis foetida community. The grassland dominated by Calamagrostis pseudophragmites and scrub vegetation were assigned to the associations previously described from Central Europe (Tussilagini farfarae-Calamagrostietum pseudophragmitae, Salici purpureae-Myricarietum germanicae and Salici incanae-Hippophaetum rhamnoidis). We established diagnostic plant species for each type using the fidelity calculation and related these types to environmental variables. We further compared them with the previously published data on gravel-bar vegetation from the Russian part of the Caucasus and with European systems of habitat classification. This study demonstrates that vegetation and habitat types occurring in Georgia correspond to those recognized earlier in Europe, and can be easily linked to the European systems of habitat classification. Unlike in other parts of Europe, these habitats are still well-preserved on rivers with natural hydrological dynamics, but they are threatened by plans of dam building and other river regulations. Our study provides baseline data for developing conservation strategies for the Caucasian gravel-bar habitats.