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Wenig bekannte Trockenrasen-Gesellschaften in den Flußtälern am Südostrand der Böhmischen Masse
(1997)
Drei wenig bekannte Festuco-Brometea-Gesellschaften aus den kristallinen Tälern der Flüsse Krems, Kamp, Thaya/Dyje, Rokytná, Jihlava, Oslava und Svitava (Südostrand der Böhmischen Masse, Österreich und Tschechische Republik) werden beschrieben. Sie kommen teilweise auf den natürlichen Waldlichtungen südexponierter Felskanten vor, teilweise auch auf sekundären Standorten. Das Inulo oculi-christi-Stipetum pulcherrimae Vicherek et Chytrý in Chytrý et Vicherek 1996 (Festucion valesiacae) ist ein Trockenrasen basischer Böden, vor allem über Marmor und permokarbonischem Konglomerat in wärmeren Teilen des Untersuchungsgebietes. Das Genisto tinctoriae-Stipetum joannis ass. nova (Festucion valesiacae) ist ein Trockenrasen, der das Inulo oculi-christi-Stipetum pulcherrimae in kühleren und niederschlagsreicheren Lagen ablöst. Sein Vorkommen ist auf Amphibolit, Marmor und Kalkstein konzentriert. Das Centaureo stoebes-Allietum montani ass. nova (Alysso-Festucion pallentis) ist ein relativ offener Trockenrasen der von beständiger Bodenerosion beeinflußten Felsterrassen auf verschiedenen (meistens basischen) Gesteinen.
A systematic survey of grassland communities in central Slovakian sub-montane and montane regions (including the Kremnické vrchy Mts., Starohorské vrchy Mts., Veľká Fatra Mts., and Zvolenská kotlina Basin) was performed between 1996 and 2007. The main aim was to identify main environmental gradients in the studied vegetation and to estimate the most important individual variables responsible for the variation of their species composition. Along with the floristic composition, the environmental variables were either recorded in the field (altitude, slope, aspect), calculated (solar radiation, climatic data, and phytochorological affinity), or derived from available maps or GIS digital data layers (type of bedrock, soil parameters). These environmental variables were used as supplementary in the detrended correspondence analysis (DCA) or explanatory in the canonical correspondence analysis (CCA). The affiliation of individual phytosociological relevés to associations was estimated by an electronic expert system for Slovak grassland communities. Altogether, 15 xero-, sub-xero- and mesophilous grassland associations were distinguished. Wet and fen meadows were analysed at the level of alliances. Unconstrained ordination revealed moisture and nutrient gradients as most important for the data set. By means of constrained ordination, the variability of the studied vegetation could be explained by a set of geological, topographic, phytochorological and derived climatic variables, although the percentage of explained variance was rather low and did not exceed 12% for all significant factors combined. Among individual variables, the geological bedrock type, climatic water balance, solar radiation, and slope played the most important role in determining the distribution and variability of individual grassland communities. Affinity to phytochorions determined according to local air temperature gradients was also significant. Soil properties played only a subordinate role in our analyses. The analysis of a more homogeneous subset of the data without wetland relevés gave similar results as the analysis of the complete data set. The differences in results of constrained and unconstrained ordinations are discussed together with the potential reasons for extremely high proportion of unexplained variance revealed by the variation partitioning methods.
Many current approaches to the formal definition of vegetation units have the disadvantage of leaving a large amount of relevés unclassified. In this paper I propose a new method for the unambiguous assignment of relevés, which is based on the summarised cover value of diagnostic species. In the first step, a relevé is assigned to the class with the highest cover score. For this purpose, the character and differential species of the class as well as the character species of all subordinated syntaxa are considered diagnostic. Once the class has been determined, the assignment proceeds successively to the lower ranks. This method, which may be called “summarised percentage cover approach”, uses solely the diagnostic species of syntaxa for the assignment of relevés to vegetation units, making additional formal definitions unnecessary. As a test data set, I used 487 relevés of fringe vegetation and grasslands of nutrient-poor sites sampled in the Vienna Woods (Wienerwald), Austria. All relevés were provisorily classified at alliances level, mostly following the assignment of the original authors. TWINSPAN and DCA were applied to evaluate this preliminary classification. Diagnostic species for both the alliance and the class level were identified using the total cover value ratio as fidelity measure. The subjective classification was largely confirmed by the numerical methods. On basis of the summarised cover of Trifolio-Geranietea and Festuco-Brometea species, between 64% (Geranion sanguinei) and 99% (Seslerio-Festucion pallentis) of the relevés were reassigned to the same class as in the original classification. The fact that a considerable amount of relevés originally classified as Geranion sanguinei was reassigned to grasslands reflects the problems in delimiting fringe communities rather than a poor performance of the assignment method. The “summarised percentage cover approach” allows not only for the unequivocal assignment of relevés to an existing classification system, but may also help to improve classifications by clarifying the delimitation of higher syntaxa.
In this paper we aim to present data on current state of steppe-like grasslands dominated by feather grasses (Stipa spp.) in the Transylvanian Lowland (Romania), and to investigate whether management type affects species composition, biodiversity, or the occurrence of rare and endangered vascular plant species in these grasslands. Twelve grassland stands, originating from nine areas and belonging to two associations, Stipetum lessingianae and Stipetum pulcherrimae from the alliance Stipion lessingianae (Festucetalia valesiacae, Festuco-Brometea), were investigated by phytosociological sampling. Our data set contains 60 relevés originating from differently managed grasslands: grazed and abandoned stands as well as former grasslands afforested with Pinus nigra. Transylvanian stands of the Stipion lessingianae occur on steep, south-facing slopes. The species composition has an accentuated sub-continental character, including several steppe elements of Siberian and Pontic origin, many of them reaching the western edge of their distribution in this region. By comparing the species composition of the two associations, we identified 12 differential species for the Stipetum lessingianae and 19 for the Stipetum pulcherrimae, but these associations also contained many species in common, which underlines their close syntaxonomic relatedness. Grazing vs. abandonment had only a slight influence on species composition and vegetation structure, while afforestation with pines resulted in strong transformations: decreased cover of the herb layer, increased cover of litter, decreased representation of diagnostic (i.e. typical) species of the two associations but increased frequency of woody, ruderal, and mesophytic grassland species. As the Stipion lessingianae belongs to the priority habitats of the Habitats Directive, these alterations call for grassland restoration measures. Our study revealed a lack of high-quality data on the vegetation of steppe-like dry grasslands in southeast Europe, where they have their largest and best-developed stands on the continent. Thus, we emphasize the need for compiling such data and for developing a consistent supranational vegetation classification of Festucetalia valesiacae communities in this region.
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.
Innerhalb geschlossener Waldbestände existieren im Naturraum Harth der elsässischen Rheinebene (Frankreich, Haut-Rhin) Lichtungen, die von artenreichen Trockenrasen-Gesellschaften bewachsen sind. Nachdem bisher von einer weitgehenden Natürlichkeit der Trockenrasen-Lichtungen in den Wäldern ausgegangen wurde, kann dieser Sachverhalt anhand von eigenen pedologischen Transektuntersuchungen und einer Aufarbeitung der vegetationsprägenden Nutzungsgeschichte differenziert betrachtet werden. Das trockene Klima wirkt im Naturraum als prägender Faktor für die Vegetation und Bodenentwicklung und läßt das pflanzenverfügbare Wasser zur entscheidenden Größe werden. Im Gebiet liegt die Grenze für lückige Waldbestände mit Lichtungen innerhalb der Colmarer Trockenzone mit durchschnitlich 600 mm Jahresniederschlägen bei rund 50 mm/m3. Die Bodenbildung wurde durch die Vegetation stark beeinflußt. Schwach saure, skelettreiche Pararendzinen und Basenreiche Braunerden ohne Kalkausfällungshorizont und mit fehlender Rubefizierung weisen bei gleichzeitig sehr geringer nutzbarer Feldkapazität (rund 50 mm/m3) auf natürlich waldfreie Standorte hin. Nur ein geringer Teil der Bodenprofile unter Lichtungen entspricht diesen Kriterien, die überwiegende Zahl der Freiflächen ist deshalb anthropogen. In zwei untersuchten Wäldern sind nach einem Luftbildvergleich 75-80% der Trockenrasen in den letzten 40 Jahren von Gebüschen bewachsen worden, was den zooanthropogenen Ursprung der Lichtungen unterstreicht. Die Trockenrasengesellschaften werden auf der Basis von 250 Vegetationsaufnahmen charakterisiert und verglichen. Im Zentrum der Untersuchung steht das Agrostio-Brometum Issler ex Oberdörfer et Korneck 1978 (V Koelerio-Phleion), das neu gefaßt wird. Syntaxonomisch gefaßt wurden aus der Klasse Festuco-Brometea das Mesobrometum Br.-Bl. ap. Scherr. 1925, eine Xerobromion-Fragmentgesellschaft und das im Gebiet an seiner westlichen Verbreitungsgrenze stehende Adonido-Brachypodietumpinnati (Libb. 1933) Krausch 1961. Das Festuco-Genistetum sagittalis Issl. 1927 (Nardo-Callunetea Prsg. 1949) des Naturraums wurde in eine eigene Subassoziation von Filipéndula vulgaris gestellt und vermittelt zu den Trockenrasen der Festuco-Brometea. Stark basen- bis kalkliebende Arten können im Naturraum nur durch die Veränderung der natürlichen Bodenhorizontierung Vorkommen. Die entsprechenden Pflanzengesellschaften (Xerobromion-Gesellschaft, Adonido-Brachypodietum pinnati) wurden durch den Menschen stark überformt. Abschließend diskutiert wird die zukünftige Entwicklung der Waldlichtungen mit Trockenrasen.
Die Steppenrasen des NSG „Badraer Lehde–Großer Eller“ werden hier erstmalig beschrieben und analysiert. 156 Originalaufnahmen wurden über eine Clusteranalyse in sieben Assoziationen und zwei ranglose Gesellschaften innerhalb der Verbände Alysso-Sedion, Seslerio-Festucion pallentis, Festucion valesiacae, Xerobromion und Cirsio-Brachypodion gegliedert. Die Auswertung alter Luftbilder zeigt, dass die beiden ranglosen Gesellschaften junge Steppenrasen auf ehemaligen Ackerflächen darstellen, während die Assoziationen überwiegend alte Steppenrasen repräsentieren. Der erste floristische Gradient nach einer NMDS in der Vegetation wird durch Variablen erklärt, die die Temperatur und die Wasserversorgung der Standorte anzeigen. Der zweite floristische Gradient kann durch das Alter der Flächen erklärt werden. Alte Steppenrasen enthalten signifikant mehr gefährdete Pflanzenarten als junge Steppenrasen, während sich der Gesamtartenreichtum zwischen jungen und alten Beständen nicht signifikant unterscheidet. Ein CSR-Strategietypenspektrum zeigt in einer Gesellschaft auf ehemaligen Ackerflächen eine höhere Bedeutung der C-Strategie, sonst aber kaum Unterschiede zwischen den Syntaxa. Die beiden Xerobromion-Assoziationen sind besonders artenreich und enthalten überdurchschnittlich viele gefährdete Pflanzenarten. Eine Gesellschaft auf ehemaligen Ackerflächen enthält durchschnittlich viele und die andere fast keine gefährdeten Arten. Der Artenreichtum der Gefäßpflanzen ist am stärksten positiv mit der Bodengründigkeit, der Deckung der Krautschicht und dem Ellenberg-Zeigerwert für Bodenreaktion und negativ mit dem Zeigerwert für Temperatur korreliert. Unsere Studie zeigt die hohe Bedeutung des NSG für den Trockenrasenschutz. Diese beruht vor allem auf der allgemein hohen Artenvielfalt und Diversität an Gesellschaften sowie auf der sehr hohen Zahl gefährdeter Arten.
The Transylvanian Plateau in Romania is well known to host large areas of a variety of dry grassland types, still traditionally managed by low-intensity mowing or grazing. While this natural heritage is now under threat from changes in agricultural practices, the diversity of Transylvanian dry grasslands is still little understood. There is a lack of both field data sampled with standardised methods and a syntaxonomic treatment with modern statistical methods and supra-regional perspective. Therefore, the European Dry Grassland Group (EDGG) carried out its first international Research Expedition in Transylvania 2009 to study syntaxonomy, vegetation-environment relationships, and biodiversity patterns of these communities. In various locations across Transylvania, we sampled 10-m² vegetation plots (n = 82) and nested-plot series from 0.0001 m² to 100 m² (n = 20), including all vascular plant, bryophyte, and lichen species, as well as structural and soil data. The vegetation classification was carried out with modified TWINSPAN, followed by determination of diagnostic species with phi values and a small-scale re-assignment of relevés with the aim of crispness maximisation. Both TWINSPAN and ordination revealed three major groups of syntaxa, which were matched to three orders from the class of basiphilous dry grasslands, Festuco-Brometea, represented by one alliance each: rocky dry grasslands (Stipo pulcherrimae-Festucetalia pallentis: Seslerion rigidae); xeric grasslands on deep soils (Festucetalia valesiacae: Stipion lessingianae) and meso-xeric grasslands on deep soils (Brachypodietalia pinnati: Cirsio-Brachypodion pinnati). We accepted nine association-level units plus two that potentially merit association status but were only represented by one relevé each. Most of the units could be identified with one or several previously described associations. To support nomenclatural stability, we provide a nomenclatural revision and designate nomenclatural types where previously there were none. Further, we used DCA ordination and analysis of variance to determine the main environmental drivers of floristic differentiation and to determine ecological and structural differences between the vegetation types. The strongest differentiation occurred along the aridity gradient with the dense, particularly diverse stands on more or less level sites on the one hand (Brachypodietalia pinnati) and the more open, less diverse stands on steep south-facing slopes on the other end of the gradient (Stipo pulcherrimae- Festucetalia pallentis, Festucetalia valesiacae). The two xeric orders were then separated along the second DCA axis, with the Stipo pulcherrimae-Festucetalia pallentis inhabiting the stone-rich sites at higher altitudes while the Festucetalia valesiacae occur on soft, deep substrata at lower altitudes. The analysed dry grassland communities have extraordinarily high -diversity at all spatial scales for all plants and for vascular plants, but are relatively poor in bryophytes and lichens. Some formerly mown stands of the Festuco sulcatae-Brachypodietum pinnati (Brachypodietalia pinnati) are even richer in vascular plant species than any other recorded vegetation type worldwide on the spatial scales of 0.1 m² (43) and 10 m² (98); the respective relevés are documented here for the first time. Also, the b-diversity of the grasslands was unexpectedly high, with a mean z-value of 0.275. Despite its limited extent, the methodological thoroughness of this study allows us to shed new light on the syntaxonomy of dry grasslands in Romania and to raise the awareness that Transylvania still hosts High Nature Value grasslands that are bio - diversity hotspots at a global scale but at the same time are highly endangered through changes in agricultural practices.
Cryophytic steppes in the Minusinskaya intermountain basin containing plant species that are predominantly distributed in the alpine zone such as Androsace dasyphylla, Dryas oxyodonta, Festuca sphagnicola, Kobresia myosuroides, K. filifolia, Minuartia verna, Oxytropis bracteata, Sagina saginoides, Papaver nudicaule, Patrinia sibirica, Pedicularis lasiostachys, Pulsatilla ambigua, Saussurea schanginiana, which are considered remnants of the Pleistocene vegetation. Based on 89 relevés, we classified cryophytic steppes using the Braun-Blanquet method within two phytosociological classes: Central Asian steppes of the Cleistogenetea squarrosae and West Palearctic steppes of the Festuco-Brometea. Three associations (Androsaco dasyphyllae-Caricetum pediformis, Pulsatillo patentis-Caricetum pediformis and Bupleuro multinervi-Helictotrichetum desertori) with three subassociations and three variants were described with respect to their phytosociological affinities and ecology. DCA ordination showed floristic differences between syntaxa, while correlations of DCA axes and floristic and environmental variables detected substrate type and temperature regime as presumably main drivers for vegetation differentiation. Another driver for vegetation differentiation seems to be continentality of the climate. Small scale distribution of cryophytic steppes were mapped using satellite images with resolution of 1.8 m. Cryophytic steppes always occupy only small areas in landscapes, on convex parts of undulated microrelief of mountain slopes and summits characterised by drought in summer and deep soil freezing in winter. These special micro-ecological conditions play an essential role for the existence of alpine flora in the Minusinskaya intermountain basin.
Im Rahmen eines Forschungsprojektes wurde die Vegetation der inselartig verteilten Porphyrkuppen im unteren Saaletal bei Halle/S. pflanzensoziologisch untersucht. Insgesamt wurden 50 Pflanzengesellschaften unterschieden, von denen nur die 13 Gesellschaften, die weitestgehend das Bild dieser Porphyrkuppenlandschaft prägen, beschrieben werden. Die Übersicht beinhaltet zum einen die für diese Landschaft typischen naturnahen Xerothermrasen (Sedo-Scleranthetalia, Festuco-Sedetalia, Festucetalia valesiacae) und Zwergstrauchheiden (Vaccinio-Genistetalia) sowie die stärker anthropo-zoogen geprägten Pflanzengesellschaften (Agropyretalia repentis, Arrhenatheretalia elatioris, Sisymbrietalia officinalis). Für die wertvollen Trocken- und Halbtrockenrasen sowie Zwergstrauchheiden lagen detaillierte Untersuchungen von MAHN (1965) und SCHUBERT (1960) vor, die für einen Vergleich des Strukturwandels der Vegetation innerhalb der letzten vier Jahrzehnte herangezogen werden konnten. Der sich vollziehende Klimawandel sowie der globale und lokale luftgetragene Stickstoffeintrag werden verschiedentlich für Artenverschiebungen sowie Vegetationsveränderungen verantwortlich gemacht. Obwohl auch wir eine Erhöhung der Gesamtartenzahlen, vor allem durch das Eindringen von Ruderalarten feststellen konnten, kann jedoch eine Gefährdung der Gesellschaften dadurch nicht konstatiert werden, da die eingewanderten Arten meist nur sporadisch und mit geringen Individuenzahlen auftreten. Dies liegt vor allem in der relativ hohen Stabilität der standörtlichen Verhältnisse begründet. Vielmehr scheint die flächenhafte Ausdehnung von Dominanzbeständen von verschiedenen Grasarten im Zusammenhang mit der seit 1990 aufgelassenen Beweidung im Zusammenhang zu stehen, die mittel- bis langfristig zu einem Umbau zu monotonen, artenarmen Gesellschaften führen kann. Für eine genaue Klärung müsste sich jedoch ein Biomonitoring der untersuchten Pflanzengesellschaften anschließen. Für die nachhaltige Entwicklung der artenreichen Xerothermvegetation ist die Wiedereinführung der traditionellen Bewirtschaftungsweise (extensive Schafbeweidung) dringend erforderlich.