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Effects of livestock on nitrogen and carbon cycling in a savanna in Burkina Faso
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International audience. The nitrogen and carbon cycles are fundamental ecosystem processes influenced by several factors including soil type and other abiotic factors, plant species, grazing and soil organisms. Herbivores profoundly influence the functioning of ecosystems and the recycling of nutrients in interaction with plants in natural ecosystems. This study focuses on the effects of livestock on carbon and nitrogen cycling in a grazed savanna in Burkina Faso. Dominant grass species (aerial and root parts) and soil samples were collected under grasses and bare soil patches in 48 plots (24 protected and 24 unprotected plots), 18 months after setting up herbivores exclosures. Soil and grass 13C and 15N were used as integrative indicators of carbon and nitrogen cycles. The results revealed no significant effect of livestock on soil total carbon and nitrogen and on soil δ13C and δ15N values. Moreover, grazing had no significant effect on grass carbon and δ13C, while it significantly increased grass total nitrogen and δ15N. Therefore, our hypothesis that grazing would increase soil 13C and 15N values and plant biomass was only verified for grass 15N. Grass δ15N results suggest that grazing improves the immediate availability of nitrogen but could also increase nitrogen losses.
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