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Central European temperate forests are – with the exception of floodplain forests – relatively little invaded by alien plants. However, despite substantial recent progress, there is still a lack of using vege-tation plot data for analyzing spatio-temporal patterns of alien tree species invasions.
We calculated relevé-based metrics of tree species’ ecological preferences using 19,413 phytosociological forest relevés of the Austrian vegetation database. We focused on the five most widely distributed alien trees, i.e. two archaeophytes (Castanea sativa, Juglans regia) and three neophytes (Acer negundo, Ailanthus altissima, Robinia pseudoacacia). For each of these species we analyzed the mean cover in the tree layer and the occurrence in the herb and shrub layers in relevés colonized by adult trees as a measure for persistence. Further, we evaluated the intergenerational ecological plasticity (= the ability of young trees to grow under different site conditions than adults) for the tree species, and the mean relevé indicator values for light, nutrients, moisture and hemeroby. We then compared these alien and native tree species metrics.
We found that A. altissima and R. pseudoacacia build up high mean cover values in invaded forests, but this was not the case for the other alien trees. Thus, both species strongly affected forest communities of invaded sites. Similarly, the two species were common in the lower vegetation layers indicating recruitment under the canopy of adult conspecifics; this was facilitated by their ability to produce root suckers. Highest values of inter-generational ecological plasticity occurred in native pioneer trees and species of softwood floodplain forests, while alien trees had moderately high (A. negundo, A. altissima, J. regia) to low values (C. sativa, R. pseudoacacia). With the exception of C. sativa, all alien species showed high mean Ellenberg indicator values for light and nutrients, and were more common in sites with high hemeroby and high mean Ellenberg indicator values for temperature. Distinct from the ecological preferences of alien trees, and thus rarely invaded, were montane beech forests, coniferous mountain forests and forests at extremely dry sites, as well as swamp and bog forests dominated by willows and ash.
We conclude that relevé-based metrics of the behavior of alien tree species allow new insights into the spatio-temporal dynamics of invasion of woody species in forests. Future work should expand this approach, e.g., by considering the role of life history traits and actual site conditions.
Durch einen Vergleich nach ca. 30 Jahren wiederholter Vegetationsaufnahmen von Glatthaferwiesen an Straßenrändern des Raumes Halle/S. konnten die in der Zwischenzeit stattgefundenen anthropogenen Veränderungen der straßenbegleitenden Vegetation am konkreten Beispiel belegt werden. Zur Interpretation der Veränderungen in der Artenzusammensetzung wurden besonders Zeigerwert-, Hemerobie- und Strategietypenspektren herangezogen. Veränderungen äußern sich vor allem in einer Abnahme der Diversität durch Zunahme euryöker Ubiquisten und einer Erhöhung des Hemerobiegrades. Die Ursachen für diesen Wandel sind besonders in der Intensivierung der Produktion auf den angrenzenden landwirtschaftlichen Nutzflächen und einer weitestgehenden Auflassung der Nutzung der Straßenränder selbst zu sehen, die sich in deren Eutrophierung äußern.
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.
The Feldbach district is situated near the town of Feldbach in the southeastern province of Styria, Austria. Since 2007, a climate observation network of 151 climate stations within an area of approximately 20 x 15 km (grid cell 1.4 × 1.4 km) has provided a unique collection of spatial and temporal meteorological data. Examining short-lived ruderal and arable weed communities, we search for correlations and spatial patterns between the community composition and climate data. Do such plant communities respond to temperature differences within an agricultural landscape and on a regional scale? Data of 277 relevés from short-lived weed communities were collected across the investigated area during the summer of 2011. Relevés were assigned to the corresponding climate stations and classified. Average Ellenberg indicator values for temperature were calculated for each relevé and community cluster. Measured temperature data were assigned and correlated with community data by applying linear regression and redundancy analyses (RDA). The classification resulted in six associations; the two most frequently observed associations were divided into subtypes resulting in 13 vegetation clusters that could be analyzed further. A significant relationship could be found only between the clusters of arable weed communities and the average winter temperatures. Site variables explain twice as much variance as measured climate variables; this ratio changes to 50 : 50 when we analyzed only arable field community data. No clear spatial patterns concerning mean annual temperature were visible. However, the Setaria faberi subtype of the Echinochloo-Setarietum and the Sorghum halepense subtype of the Convolvulo-Agropyretum show a tendency toward a temperature-induced spatial pattern, such that both were sensitive to winter temperature. On a regional scale, the occurrence and composition of short-lived ruderal plant communities correlated weakly with climate variables. However, the studied arable weed communities showed a certain tendency to follow small-scale temperature differences, especially those of average winter temperature. We conclude that short-lived weed communities have the potential to be indicators for global warming, but the spatial temperature gradients are not clear enough in our approach to allow the production of better regression models and elucidation of distinct spatial patterns.
Unter diesem Titel trafen sich mehr als 180 Tagungsgäste aus allen botanischen Gruppierungen - Naturschutzfachvereinigungen, Universitätsinstitute, Sammlungen, Behörden und Ämter sowie Freiberufliche - vom 18. bis 20. November 2005 im Göttinger Albrecht-von-Haller-Institut für Pflanzenwissenschaften der Georg-August-Universität. Eingeladen hatte die Abteilung Vegetationsanalyse und Phytodiversität (Erwin Bergmeier) des AvH-Instituts und der Bundesfachausschuss Botanik des NABU in Zusammenarbeit mit den botanischen Vereinigungen der Länder (Christian Berg, Michael Ristow). Ausgangspunkt der Tagung war die Einsicht, es mangele in Deutschland zunehmend an Strukturen, um Konzepte und Ziele aufzugreifen, die im internationalen Naturschutz angestoßen worden sind, und sie als Chancen zu nutzen. So sind die Ziele der ,Globalen Strategie zum Schutz der Pflanzenwelt' (Global Strategy for Plant Conservation, GSPC), dem wohl wichtigsten Instrument des internationalen Florenschutzes, bei uns noch viel zu wenig bekannt. Auch fehlt ein nationales Forum, in dem Ideen und Erfahrungen im botanischen Naturschutz ausgetauscht werden können. Ziel der Tagung war es daher, Wege zur Umsetzung der GSPC zu diskutieren und allgemein einen Prozess in Gang zu bringen, um den Informations- und Ideenaustausch zu verbessern, eben ein Netzwerk für alle, die dem Florenschutz verpflichtet sind, zu fördern.