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Evidence for increasing homogenization and de-ruralization of the Central European village flora
(2013)
In this study, the spontaneous flora of North Rhine-Westphalian villages (NW Germany) recorded in the periods 1980–1984 and 2004–2005 was analyzed. We asked: (i) Did the similarity of the village flora increase with time and to what extent did non-native species contribute to this? (ii) Is the ongoing trend of urbanization reflected in the village flora? (iii) Regarding the species composition and β-diversity: are there differences between the results of a repeated survey and of a type comparison? In both periods, 200 villages were visited once, using consistent criteria for village selection and floristic investigation. Of these, a subset of 61 villages was investigated in both time periods and the rest were selected randomly for the second survey but with respect to the same criteria as used in the first. Using different β-diversity indices (Sørensen index of dissimilarity, Simpson index of dissimilarity and nestedness resultant index) to disentangle pure species turnover and nestedness of species assemblages, we tested whether the similarity among the villages increased over the years. This was done by calculating all pairwise comparisons among the villages of each time period, i.e. their spatial turnover. Additionally, different ecological groups were defined (e.g. "neophytes", "C-strategists" or "urbanophilous species") using the subgroups of species traits (floristic status, Grime's life strategy and urbanity) to indentify urbanization and compositional changes. Our results show that the traditional village flora (species of the Arction lappae, Bidention tripartitae and Potentillion anserinae) is further blurred towards unspecific ubiquitous assemblages found in the periphery of man and that the floristic urbanization is still ongoing. Supported by nearly all ecological groups regarded, our results corroborate that the species composition of Central European villages underwent a considerable degree of homogenization. To some extent this is caused by structural homogenization of villages. Regarding the considerable increase of common ubiquists and α-diversity in general, however, changes in weeding practices seem to be the main reason. Based on the reinvestigated subset we could show that comparable results can be obtained by a consistent use of criteria for the selection of villages, even if unpaired samples were used.
In September 2005, one male specimen of the wolf spider genus Alopecosa was discovered and photographed in heathland near Haltern, North Rhine-Westphalia, Germany. It was identified as A. barbipes (Sundevall, 1833), as it showed the species- and sex-specific tibial hair-brush absent in the sibling species A. accentuata. Three years later, two other specimens of A. barbipes were collected in the same area. These findings indicate that the species is more widespread than originally thought. Some details concerning the distribution of A. accentuata and A. barbipes and the problem of synonymy are discussed.
Im westlichen Teil des Ballungsraumes Ruhrgebiet hat sich trotz der Flächenansprüche seit der Industrialisierung ein großflächiges Altwaldgebiet mit einer Vielfalt unterschiedlicher naturnaher Waldgesellschaften erhalten. Im Rahmen einer floristisch-vegetationskundlichen Untersuchung dieses „Duisburg-Mülheimer Waldes“ wurden schwerpunktmäßig die Birkenbruch- und Erlenbruchwald-Bestände bearbeitet (FUCHS 2003).
Das Carici elongatae-Alnetum muss als durchweg gestört betrachtet werden, weist aber im Gegensatz zum Birkenbruch ein erstaunlich vollständiges Artenspektrum auf. Deutlich lässt sich ein nährstoffarmer Flügel als Carici elongatae-Alnetum betuletosum pubescentis, ein nährstoffreicher Flügel als C.-Al. iridetosum sowie das C.-Al. cardaminetosum auf quelligem Standort abgrenzen. Das Betuletum pubescentis ist aktuell im Untersuchungsgebiet lediglich als Fragmentgesellschaft vorzufinden.Vor dem Hintergrund der Beeinträchtigungen und Belastungen durch den Ballungsraum werden der Zustand, das Potenzial und die Entwicklungstendenzen der Birken- und Erlenbruchwälder diskutiert. Mit der teilweisen Wiedervernässung und einer gezielten Besucherlenkung wird es für möglich gehalten, den Status quo der Birkenbruchwälder zu stabilisieren und den Zustand der Erlenbruchwälder zu verbessern. Auf diese Weise könnten auf lange Sicht die Birkenbruch- und Erlenbruchwälder für den Ballungsraum Ruhrgebiet erhalten werden.