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Die weidewirtschaftliche Nutzung beeinflußt seit Jahrtausenden den Natur- und Kulturraum der westafrikanischen Savanne. Die Beweidung durch die verschiedenen domestizierten Tierarten hat in diesem Zeitraum einen wesentlichen Einfluß auf die Entwicklung der Vegetationszusammensetzung gehabt und das vor allem in der Krautschicht. Übermäßige Beweidung kann - wie zahlreiche Untersuchungen zeigen - zu einschneidenden Veränderungen in der Pflanzendecke führen, die letztlich in einer völligen Zerstörung der Vegetation gipfeln können. Dieser Prozess wird landläufig als Überweidung bezeichnet und gilt als eine der wesentlichen Ursachen für Landschaftsschäden. Die in den letzten Dekaden ständig anwachsenden Tierbestände in Afrika südlich der Sahara haben die Situation weiter verschärft. Folgerichtig konzentrieren sich Meliorationsvorschläge auf eine Verringerung der Besatzdichte auf ein tragfähiges Maß. Angestrebt wird ein geregeltes Weidemanagement, das eine nachhaltige Bewirtschaftung der natürlichen Ressourcen ermöglicht. Trotz teilweise jahrzehntelanger Bestrebungen konnte dieses Ziel bis dato nicht erreicht werden, so daß in jüngerer Zeit Fachwissenschaftler zu der Überzeugung gekommen sind, daß diese Mißerfolge bereits auf Fehler in den grundlegenden Überlegungen zurückzuführen sind. Die aus diesen neuen Überlegungen resultierenden Modellvorstellungen in der Weideökologie sollen an dieser Stelle vorgestellt werden. Dabei wird vor allem auf die Problematik der Beurteilung und Bewertung des Überweidungsprozesses eingegangen.
The study investigates elements influencing agricultural development in villages of the hinterland of Gombe, Gombe State, Nigeria. It aims to discover changes in socio-economic and socio-cultural interactions that exist among household, region, nation and world market. Of special interests are rural households as well as wholesale markets where dynamic processes in the structure of agricultural enterprises and the individual reasons of innovations are recognisable. The final objective of the study is to analyse the agricultural sector in the investigated villages in time and space, by typifying rural households, there strategies of action in relation to different factors: for example, farmsize, cultivation techniques and marketing of agriculture products. The study is also interested in operational profits and costs of farms, income of households as well as expenditures, etc. Because of the fact that statistical work is still going on, it is only possible to present a small portion of the results. Namely, the change in cultivation and marketing of farm products with special emphasis on cash crops during the last 30 years.
Correction to: Apidologie (2020) 51:1182–1198
https://doi.org/10.1007/s13592-020-00796-9
The article Insights into Ethiopian honey bee diversity based on wing geomorphometric and mitochondrial DNA analyses, written by Hailu, T.G., D’Alvise, P., Tofilski, A. et al., was originally published Online First without Open Access. After publication in volume 51, issue 6, page 1182-1198, the author decided to opt for Open Choice and to make the article an Open Access publication. Therefore, the copyright of the article has been changed to © The Author(s) 2020 and the article is forthwith distributed under the terms of the Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution, and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article is included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. Open Access funding enabled and organized by Projekt DEAL.
Within the world’s oceans, regionally distinct ecological niches develop due to differences in water temperature, nutrients, food availability, predation and light intensity. This results in differences in the vertical dispersion of planktonic foraminifera on the global scale. Understanding the controls on these modern-day distributions is important when using these organisms for paleoceanographic reconstructions. As such, this study constrains modern depth habitats for the northern equatorial Indian Ocean, for 14 planktonic foraminiferal species (G. ruber, G. elongatus, G. pyramidalis, G. rubescens, T. sacculifer, G. siphonifera, G. glutinata, N. dutertrei, G. bulloides, G. ungulata, P. obliquiloculata, G. menardii, G. hexagonus, G. scitula) using stable isotopic signatures (δ18O and δ13C) and Mg/Ca ratios. We evaluate two aspects of inferred depth habitats: (1) the significance of the apparent calcification depth (ACD) calculation method/equations and (2) regional species-specific ACD controls. Through a comparison with five global, (sub)tropical studies we found the choice of applied equation and δ18Osw significant and an important consideration when comparing with the published literature. The ACDs of the surface mixed layer and thermocline species show a tight clustering between 73–109 m water depth coinciding with the deep chlorophyll maximum (DCM). Furthermore, the ACDs for the sub-thermocline species are positioned relative to secondary peaks in the local primary production. We surmise that food source plays a key role in the relative living depths for the majority of the investigated planktonic foraminifera within this oligotrophic environment of the Maldives and elsewhere in the tropical oceans.