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Ambrosia artemisiifolia is an invasive annual herb infamous for the high allergenicity of its pollen, which is related to increasing medical costs. Additionally, it can cause serious yield losses as agricultural weed. Common ragweed seeds accumulate in the soil and can remain therein viable for decades, which poses a problem for the sustainable management of these populations. A long term management should thus target a reduction of the soil seed bank. We observed the influence of four different mowing regimes on the ragweed soil seed bank at six roadside populations in eastern Austria. The mowing regimes were based on methods from common roadside management practice and specifically adapted to reduce seed production. After three years of application, the soil seed bank was indeed reduced by 45 to 80 percent through three of the four mowing regimes tested. Therefore, we suggest that the best mowing regime for the most effective reduction of the size of the soil seed bank is the one consisting of one cut just after the beginning of female flowering (around the 3rd week of August in Eastern Central Europe), followed by a second cut 2–3 weeks later.
The vast majority of European grasslands strongly depend on the regular removal of aboveground biomass by agricultural land use, mostly grazing or mowing or a combination of both. These specific management schemes have strong influence on plant diversity and vegetation composition, depending on their particular characteristics and their intensity. For example, the presence or absence of fertilization will favour some species over others, changing plant communities accordingly. Additionally, the farmer’s choice of a specific management scheme will also depend on the abiotic site conditions. This leads to a complex set of associated factors potentially affecting the structure and diversity of grasslands.
In this study, we compiled a unique dataset of 169 differently managed grasslands (in total 202 plots), which were sampled in five regions across Germany. For each plot, we documented management characteristics, measured plant diversity and functional group composition, recorded endangered species according to red lists, and calculated Ellenberg indicator values. We assessed patterns in vegetation composition and diversity in relation to the particular management scheme, which was categorized as meadow, meadow with autumn or winter grazing (with mowing as predominant management), mown pasture (where mowing and grazing are used at roughly equal intensity), seasonal pasture (with grazing as predominant management) and year-round pasture.
Our study showed that grasslands of different management schemes significantly differed in diversity, structure and functional composition. However, it also became obvious that vegetation composition was not strictly distinguished by management alone. Local and regional characteristics such as soil conditions, size of the grassland species pool or land-use history, often played a more prominent role than land use alone. Assumingly, the interplay of those local and regional characteristics with the proportion of grazing and mowing at a particular site inhibit clear differences among our predefined management schemes. Nevertheless, species richness was the lowest in year-round pastures, moderate in meadows and highest in seasonal pastures. In contrast, year-round pastures harboured the highest mean numbers of endangered species. The dependency of a certain management scheme on site-specific environmental factors such as soil fertility, further complicated the clear separation of management effects from those of the environmental background. In summary, modern grassland management strongly shaped grassland vegetation, but today’s combination of different management practices complicated the assessment of specific land-use effects on plant diversity. Thus, neither mowing nor grazing turned out to be “the one and only” management for nature conservation. Although our results challenge long-term prognoses for future vegetation development under modern grassland management, we clearly showed that low-intensity management and the absence of fertilization promoted plant diversity, with higher values in pastures compared to meadows and mown pastures.
Semi-dry grasslands were once widely distributed communities, but today they represent some of the most vulnerable habitats in Central Europe. European and national legislation and non-governmental organizations have managed to protect some of the remaining fragments. However, despite their status as Natura 2000 habitats, they are often endangered due to improper management, fragmentation and edge effects from adjacent croplands. By using a sample of 44 semi-dry hay meadows in the south-eastern Alpine Foreland of Styria, we investigated how species-richness and trait composition of semi-dry grassland species respond to variation in patch size, connectivity, abiotic site factors and management regimes. We used linear regression models to identify the most important drivers for richness of typical semi-dry grassland species and thus conservation value. The number of typical semi-dry grassland species was highest in well-connected fragments, i.e. units that shared two or more borders with neighbouring species-rich grasslands. Furthermore, large semi-dry grasslands (> 8000 m²) had highest numbers of semi-dry grassland species and highest relevance for conservation; no difference was found among smaller fragment sizes. Unregular management was associated with increased presence of competitive species which replaced stress-tolerant specialists. Our study indicates that under eutrophication, small fragment size and isolation, only large semi-dry grasslands can sustain a high number of species with high conservation value. The conservation value of smaller semi-dry grassland fragments could be improved by buffer zones, adapted mowing treatments and periodical sheep grazing.
Steppes used to cover large areas of Hungary, but most of this vegetation has since been destroyed. In Central Hungary, some patches have survived on ridges in wet meadows. These habitat complexes face profound land use changes and their optimal management regime is uncertain. We identified seven annually mown steppe and wet meadow types according to their grazing regime and history and aimed to answer the following questions: (1) Does grazing have beneficial effects on mown steppes and wet meadows? (2) Should the presently homogeneous management of neighbouring steppes and wet meadows be maintained? (3) Is annual mowing sufficient in assisting the recovery of steppes and wet meadows on former croplands?
We selected three localities for each of the seven vegetation types and sampled them with 50 quadrats (50 × 50 cm) in each locality, making a total of 1,050 quadrats. Vascular plant diversity relations were evaluated using the total number of species per habitat type (species richness) and the average number of species per quadrat (microsite diversity). The effect of grazing and history on microsite diversity was tested with linear mixed-effect models. We used Redundancy Analysis to disentangle the role of grazing intensity and management history on species composition. Plant species were then sorted into functional groups, and the proportions of these groups were used to evaluate community structure.
Our results indicate that mowing alone cannot maintain as high a diversity as the combination of the two land use types, thus grazing should be introduced to non-grazed areas. Steppes, however, were found more sensitive to the intensity of grazing than wet meadows. Under heavy grazing, no increased microsite diversity was detected in the steppes and the proportion of disturbance indicators tended to increase. In contrast, the same grazing intensity resulted in only positive effects in wet meadows. Thus, uniform land use on adjacent steppes and wet meadows is not recommended but intensive grazing should be stopped on steppes. Secondary steppes were less diverse than primary ones and their community structure was also poorer, whereas wet meadows had a better regeneration potential. Thus, mowing alone is an incomplete tool to restore the plant diversity of secondary steppes; they should also be grazed and/or should be supported by other active interventions.
The complex topography of floodplains provides conditions for high diversity and density of transitional areas between different grassland plant communities. Nevertheless, transitions have been almost completely neglected in previous studies of diversity patterns in semi-natural floodplain grasslands. We analyzed α-, β- and γ-components of plant species diversity in transitional areas between neighbouring wet and dry grassland communities in two landscapes of the Gauja River floodplain (Latvia) differing in landscape heterogeneity created by land use history and current management type (grazing versus mowing). In total 9 transition areas and their adjacent vegetation were sampled in 1 m wide and 8 to 28 m long belt transects gridded into 0.5 m × 1 m plots. Cluster analysis was used to analyze varia-tion in species composition of transitional areas and adjacent vegetation. Indicator species analysis was used to determine species specific to transitional areas (ecotonal species). Transitional areas of the homogeneous site had a more distinct species composition (clear division in clusters by cluster analysis) and significantly lower β-diversity than those of the heterogeneous site. α-Diversity was significantly higher in transitions than in wet grasslands and lower than in dry grasslands in both sites. Comparing the two sites, α-diversity was significantly higher in wet grasslands of the heterogeneous site, but no differences were found between transitions and dry grasslands in the two sites. Higher β-diversity of transitional areas in the heterogeneous site could be attributed to a higher density of different habitats per unit area in combination with grazing. No species were restricted to transitions, and no differences were apparent in the number of generalist species (indifferent species sensu Ellenberg indicator values for edaphic factors) between transitions and adjacent grasslands. Nevertheless, the total number of generalist species was considerably higher in the investigated flood-plain grasslands than usually reported for respective vegetation types in Latvia. It was concluded that transitions of neighboring floodplain grassland plant communities were more important in shaping β-diversity compared to α- and γ-diversity. Our results suggest that destroying transitional areas between dry and wet grasslands by leveling the ground or by abandonment of the management practices will decrease habitat heterogeneity and lead to less pronounced ecotonal pro-cesses in the whole riverine landscape. Thus further studies about the role of fine-scale transitional areas for biodiversity of floodplains are important for ecological restoration of floodplain grasslands.