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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.
Naturalness is one of the most important criteria in nature conservation. This paper examines the fundamental concepts underlying the definition and assessment of naturalness. Its role in nature conservation and forest management under conditions of global change is also discussed. The degree of naturalness may be defined in ordinal classes. The “static” concept of the potential natural vegetation (pnV), developed in the 1950ies, is mostly used as the reference state. In other cases, its reversed concept, the hemeroby (degree of articifiality) is assessed, based on the intensity and frequency of human impacts. Since the 1970ies, more attention has been given to natural dynamics than in earlier approaches, e.g. in forest succession models. At the end of the 1980ies, the previous importance was increasingly stressed of natural browsing by large herbivores and the role of predators. These large herbivors are extinct today in most cultural European landscapes. It is assumed, that they open up the canopy, and create park-like forest structures which contain a diversity of habitats for other types of organism (birds, insects). Changed and permanently changing environments and altering patterns of competition between species continue to modify natural processes today. Some of the more conspicuous effects are the extinction of native species and immigration of species to new regions. Long-lived ecosystems like forests are however not able to adapt quickly to such changes and may be unable to find a new balance with the environment. Today, such changes occur very rapidly, and are reducing the original naturalness of ecosystems. Because of this, the criterion “naturalness” must be downweighted. Conversely, more importance should be attached to other criteria: particularly originality (= original naturalness) and restorability. Forestry is contributing to this accelerated change of biocoenoses by increasing disturbances and introducing exotic tree species. Naturalisation of some exotic tree species modifies the natural processes and creates a “new allochthonous naturalness”. Because of this, forest planning should try to preserve or restore stands with attributes of the “original forest”. Exotic species should not be planted, or only in a very restricted way.
Die Literaturstudie befasst sich mit Bewertungsmöglichkeiten der Natürlichkeit von Ökosystemen anhand biotischer und abiotischer Merkmale verschiedener Kompartimente. Schwerpunktmäßig wird die Indikatoreignung des Bodens berücksichtigt. Es wird festgestellt, dass durch die meisten Untersuchungsansätze nur der aktuelle Zustand der Ökosystemkompartimente oder ihre Beziehungen untereinander und damit der Hemorobiegrad des Systems (des Bestandes) abgeschätzt werden können. Demgegenüber ist die Analyse von Bodeneigenschaften geeignet, die Natürlichkeit auch in historischer Perspektive, also die Naturnähe i. e. S., festzustellen. Vor dem Hintergrund des mehrstufigen biologischen Diversitätskonzeptes von Whittaker (1972) wird der Frage nachgegangen, ob sich im Hinblick auf die einzelnen Kompartimente (1) das Auftreten spezifischer Merkmale (Merkmalspräsenz), (2) die Intensität, Menge, Abundanz (Merkmalsausprägung), (3) die Variabilität des Merkmals (alpha-Ebene) und (4) die räumliche Heterogenität bzw. Verteilung des Merkmals (beta-Ebene) zur Bewertung von Natürlichkeit eignen. Die genetische Variabilität der bestandesbildenden Baumart kann ein Merkmal für Naturnähe und Autochthonie sein, wenn die jeweilige Populationsbiologie berücksichtigt wird. In der Literatur werden tierische und pilzliche Urwaldzeigerarten beschrieben, während sich einzelne Gefäßpflanzen sowie die Artenanzahl (alpha- von Pflanzen, Pilzen und Tieren nicht zur Indikation eignen. Eine geklumpte Verteilung biologischer Arten (beta-Diversität) innerhalb des Ökosystems stellt ein gutes Natürlichkeitskriterium dar. Bei den Kompartimenten Bestandesstruktur und Boden können sehr viele Merkmale verschiedener Hierarchieebenen herangezogen werden, um Natürlichkeit abzuschätzen. Da Bodendiversität und -heterogenität i. d. R. verschiedene Ursachen haben, werden diese in ihrem Bezug zu Naturnähe bzw. Hemerobie erläutert. Keywords: naturalness, genetics, flora, fauna, fungies, stand structure, soil properties, α-diversity, β-diversity, variability, heterogeneity, autocorrelation, archive function