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Die Makrophytenvegetation eines stillgelegten Kanalabschnittes ("Alte Fahrt") bei Senden in Westfalen hat sich seit Beginn der 90er Jahre drastisch verändert. Aus einem typischen Potamogetonetum lucentis sind Reinbestände von Myriophyllum spicatum geworden, denen stellenweise Ceratophyllum demersum beigemischt ist. Die Ursachen für diese gravierenden Vegetationsveränderungen sind nicht klar. Da es sich um einen der bedeutendsten westfälischen Standorte des Potamogetonetum lucentis, einer in Nordrhein-Westfalen stark gefährdeten Pflanzengesellschaft, handelte, sind weiterführende Untersuchungen und Versuche zur Wiederansiedlung zu fordern.
In West African savannas, human land use affects the density of woody species seedlings and saplings (juveniles) by altering the state of the physical, chemical, and biological characteristics of the land resulting in different land-cover types. We determined juvenile densities of 25 characteristic woody savanna species on non-arable sites, in fallows and in a protected area (in total 39 plots), and analyzed the influence of land use on juvenile densities. We further related the influence of land use on juvenile densities to 23 environmental parameters describing soil properties and vegetation structure. Soil acidity, particle size distribution of the soil, and vegetation structure differed between land-cover types. In terms of human impact, we detected five groups of species responding similarly to land use. Although we detected significant differences in soil properties, their direct effects on juvenile densities are less pronounced than their indirect effects. By altering the availability of resources, soil properties affect height and cover of all plants growing in the surrounding of a young woody plant, increasing the competition for light, water and nutrients during the establishment and initial growth. These effects are intensified by human land use and vary between land-cover types.
In spite of enormous climatic differences between Burkina Faso and Germany, 20 species belong to the spontaneous flora of both countries, i.e. 1% of the flora of Burkina Faso and 0.15 % of the German flora. All of them are either ruderal and segetal species (16) or water and reed plants (4). All of the 16 ruderals/segetals are therophytes. From a recent point of view, most of the 20 species can be classified as cosmopolitan, because they cover three and more floristic zones, and/or at least three climatic zones, and/or are represented in at least three continents. Although Burkina Faso has a semi-arid climate, none of the species can be called a sclero- or xerophyte. Therefore, in Burkina Faso, all are more or less bound to habitats at least temporarily flooded or to humid soils. In Germany, however, the concerned ruderals, with one exception, are indicators of medium dry or dry habitats.
Particularly in savannas, termites are ecosystem engineers and a keystone group in ecology. For the understanding of the savanna vegetation, mound building termites are of particular interest. Due to their special soil chemistry and physical structure, termite mounds often host other plants than the surrounding savanna. As our knowledge of the specific contribution of mound-building termites to overall savanna diversity and ecosystem dynamics doubtlessly is not complete, this paper summarises the state of the art in order to stimulate further research. According to the research interest of the authors, focus is laid on the West African savanna and on the genus Macrotermes.
Dem Wandel rechtzeitig begegnen : Landesförderung ermöglicht richtungsweisende Klimafolgenforschung
(2008)
Ohne das Eingreifen des Menschen wäre Mitteleuropa fast ein reines Waldgebiet. Noch heute beheimaten die Wälder eine große Vielfalt an Pflanzen und Tieren, die für diese Region spezifisch sind. Regionale Besonderheiten gehen aber verloren, je mehr Menschen in die Ökosysteme eingreifen: So unterscheiden sich die Pflanzenarten auf der North Charles Street in Baltimore nur wenig von denjenigen der Mainzer Landstraße in Frankfurt. Gleichzeitig verdrängen zugewanderte und eingeschleppte Arten heimische Tiere und Pflanzen. Allerdings gibt es auch im Frankfurter Stadtgebiet echte Horte der Biodiversität.