PhD cremony Ms. S. Nolte: Grazing as a nature-management tool. The effect of different livestock species and stocking densities on salt-marsh vegetation and accretion

PhD ceremony: Ms. S. Nolte

Dissertation: Grazing as a nature-management tool. The effect of different livestock species and stocking densities on salt-marsh vegetation and accretion

Promotor(s): prof. J.P. Bakker

Faculty: Mathematics and Natural Sciences

Cattle and horses show different behavior with respect to diet composition, activity and spatial distribution in salt marshes, concludes Stefanie Nolte in her thesis. Grazing with livestock is successfully used as a nature-management tool to increase or restore biodiversity in many grassland ecosystems such as Western European coastal salt marshes. Which grazing management to apply is, however, still a point of consideration. Therefore, an experiment was required to study the effects of different stocking densities and livestock species on the vegetation of salt marshes. In order to understand differences in the impact of livestock species on vegetation, we need to understand the differences in their behaviour. Therefore, Nolte studied the behaviour of horses and cattle with respect to diet choice, activity and spatial distribution. These behavioural differences between livestock species and stocking densities are likely to affect the vegetation on different scales: the plant species level, the community level, and the vegetation-structure level. Nolte investigated the effect on the flower production of a target plant species, namely Aster tripolium, on plant-species composition and small-scale vegetation structure. The observed effect of grazing on the vegetation structure might also affect the abiotic conditions in salt marshes. Nolte tested the hypothesis that accretion rates would be lower in grazed compared to ungrazed marshes because of increased soil compaction by trampling and reduced sediment deposition in short vegetation. In addition to the accepted importance of stocking density as a key variable in management schemes, she was able to identify differential effects of two livestock species on vegetation. Therefore, Nolte emphasizes that livestock species should be carefully chosen with respect to the management target.