Tropentag, September 11 - 13, 2024, Vienna "Explore opportunities... for managing natural resources and a better life for all"

Short-term effect of water regimes and defoliation on sahelian vegetation dynamics using stable isotopes

¹Cheikh Anta Diop University of Dakar (UCAD), Senegal
²Georg-August University Göttingen, Dept. of Crop Sciences, Grassland Science, Germany
³Centre de coopération Internationale en Recherche Agronomique pour le Développement (CIRAD), UMR SELMET, France
⁴Georg-August University Göttingen, Dept. of Crop Sciences, Grassland Science, Germany
⁵CIRAD, 34060, France, UMR Eco&Sols,, France
⁶Georg-August University Göttingen, Department of Crop Sciences, Grassland Sciences, Germany
⁷Cheikh Anta DIOP University, Department of Plant Biology, FST/UCAD, Senegal

Abstract

Grasslands in semi-arid ecosystems play an essential role in livestock production. In the Sahel, pastoral livestock production mainly relies on vegetation dynamics for livestock feeding. However, the feed resources are predicted to be affected by increased drought conditions and increased human exploitation. This study aimed to understand the effects of variable rainfall patterns and defoliation on herbaceous vegetation in the Sahel region. A rainout shelter experiment was conducted at the natural rangeland in Dahra, Senegal during the rainy season (May to October 2022). The experiment consisted of a factorial combination of four water regimes (WR) with or without defoliation and one control (C, natural rainfall, 306 mm), replicated twice. The WR refers to two wet treatments that received more than the natural rainfall (differing by water application interval, W1 and W2, 562 mm) and two dry treatments that received less than the natural rainfall (differing by periods of break D1 and D2, 200 mm). The results showed that the accumulated aboveground (AGB) and belowground (BGB) biomass were influenced by WR only (p < 0.01, p = 0.02, respectively). This is indicated by higher AGB and BGB under the wet treatments. Moreover, the isotopic analysis i.e. δ¹³C values for AGB and BGB and δ¹⁵N BGB were not influenced by neither WR nor defoliation (p > 0.05). However, δ¹⁵N AGB values were strongly influenced by WR (p < 0.01). The allometric relationships showed significant correlation between AGB and BGB in one part, and between δ¹⁵N AGB and δ¹⁵N BGB (r² = 0.59 and 0.72, respectively p < 0.01). The dominant effect was consistently revealed by water regime, a clear indication of the impacts of rainfall patterns on vegetation dynamics. These results might be helpful for the management of semi-arid and arid grassland livestock systems.

Keywords: Carbon, forage, grazing, livestock systems, nitrogen, pastoralism. , rangeland biomass, sahel, Senegal

Contact Address: Adjoua Ange-Jokebed N'Goran, Cheikh Anta Diop University of Dakar (UCAD), Dakar, Senegal, e-mail: jokebedngoranhotmail.com