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Universitat Hamburg (1999)

The scale-dependent variability of topsoil properties reflecting ecosystem patchiness in drylands of Southern Africa

Herpel, Nicole

Titre : The scale-dependent variability of topsoil properties reflecting ecosystem patchiness in drylands of Southern Africa

Auteur : Herpel, Nicole

Université de soutenance : Universitat Hamburg

Grade : Doktorgrades der Naturwissenschaften 1999

Résumé
A part of the ecosystem, soils control the composition and abundance of plants and animals and vice versa. Thus biodiversity and pedodiversity are directly linked and also reflect geologic, topographic, climatic and anthropogenic influences. In drylands, small scale patchiness of soil properties and vegetation affects the distribution of water and nutrients and therefore ecosystem functions. However, despite this obvious significance, processes linking pattern and scale are not yet completely understood in these environments. Therefore, this work aims at investigating the variability of topsoil properties, their scale-dependent patterns, their drivers and underlying processes with the focus on the micro- (dm2 - 1 m2) and the mesoscale (1 m2 - 1000 m2). The work was conducted within the scope of the BIOTA Southern Africa project and ties in with the work of Petersen (2008), who analysed soils on a habitat and landscape scale on the same sites. Field work was conducted on or in direct vicinity to three standardised BIOTA observatories of which the "Soebatsfontein" observatory was located in the Succulent Karoo of South Africa and "Gellap" and "Nabaos" in the Namibian Nama Karoo. The study sites were comparable in terms of geologic and geomorphologic diversity and the annual amount of precipitation ; yet they differed in rain regime (Succulent Karoo : winter rain, Nama Karoo : summer rain), vegetation and landscape dynamics. The two sites in the Nama Karoo were furthermore differentiated by contrasting landuse practices (Nabaos : communal open access farming, Gellap : commercial land management with fenced camps and grazing control). A special feature of Soebatsfontein is the occurrence of fossil termite mounds, so-called "heuweltjies", in the landscape that exhibit

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