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Technische Universität Berlin (2020)

Land-use effects on plant biodiversity and carbon cycling in seasonally dry tropical forests in north-eastern Brazil

Schulz, Katharina

Titre : Land-use effects on plant biodiversity and carbon cycling in seasonally dry tropical forests in north-eastern Brazil

Auswirkungen der Landnutzung auf die Pflanzendiversität und den Kohlenstoffkreislauf in tropischen Trockenwäldern in Nordostbrasilien

Auteur : Schulz, Katharina

Université de soutenance : Technische Universität Berlin

Grade : Doktor der Naturwissenschaften - Dr. rer. nat. - 2020

Résumé partiel
One of the most threatened ecosystems of Brazil is the so-called ‘Caatinga’. It is the seasonally dry tropical forest located in north-eastern Brazil. Due to the semi-arid climate, livestock husbandry (mainly goats) is the main economic sector. However, besides high stocking densities free roaming animals aggravate the degradation of this ecosystem. In areas near the Itaparica Reservoir, irrigation farming is conducted with perennial plants such as coconut, banana, guava, and mango and annual crops such as onion and melon being the most common crop species. Here, typical problems such as a high usage of agrochemicals and an improper irrigation, often leading to salinisation of the soils, occur.

The present thesis analyses the effect of different land-use practices and intensities on the plant diversity and organic carbon stocks in an area of Caatinga seasonally dry tropical forest.

The data assessment was carried out on 45 permanent study plots in the Caatinga dry forests (Itacuruba and Floresta) and on 21 agricultural areas in the irrigation schemes Apolônio Sales and Icó-Mandantes (Petrolândia). In the dry forests, the grazing intensity was quantified for each plot. The diversity of perennial plant species was recorded on a 20 m × 20 m plot (abundance). Herbaceous species were assessed on four subplots (each 2 m × 2 m) using the Braun-Blanquet cover-abundance scale. Further, the aboveground carbon stocks of woody plants (subplot, 10 m × 10 m) and herbaceous species (two subplots, each 2 m × 2 m) were assessed. For analysing soil organic carbon stocks, three samples of the topsoil and samples of two soil profiles were taken in each Caatinga plot.

On the agricultural fields, two study plots (each 5 m × 5 m) were established. On these plots, vegetation relevés of weed species were carried out (cover-abundance scale according to Braun-Blanquet). Further, crop plants were measured to estimate the biomass per crop plant. Soil organic carbon stocks were determined by analysing two samples of the topsoil per study plot.

Mots clés  : semi-arid ; seasonally dry tropical forest ; land use ; plant biodiversity ; organic carbon ; semiarid ; tropischer Trockenwald ; Landnutzung ; Pflanzendiversität ; organischer Kohlenstoff

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