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Of dwarves and giants; How large herbivores shape arthropod communities on salt marshes

19.06.2014 11:04 Age: 4 years
Category: Ecologie, English

Livestock grazing is a commonly applied management type to maintain plant species richness on coastal salt marshes and other grassland types. The effects of this grazing management on invertebrates, however, are generally neglected. This thesis assesses how invertebrate communities are affected by grazing management, with regard to grazer species and density as well as rotational grazing (annual rotations of grazed and ungrazed years).

Grazing on salt marshes. Foto: TS

Plant species richness is often increased by grazing. This happens largely through a decrease in competition for light, since large grazers consume tall plant species, creating possibilities for short-statured plant species. My research, however, shows that invertebrate species richness usually decreases under grazing management. Especially on salt marshes, many invertebrate species depend on tall vegetation as a source of food or protection from inundations. When this vegetation is consumed by large grazers, many of the food sources and habitats of invertebrates will decrease or disappear, leading to a decline in species richness.

Stocking density is the most important factor determining how invertebrate species richness is affected by grazing, since it determines the amount of biomass that is consumed. The species of livestock used for management seems to play a minor role. The chances for preserving species richness of invertebrates, as well as plants and birds, are increased when heterogeneity is maximised. This can be achieved by maintaining differently managed areas in close proximity, maintenance of low stocking densities in large and continuous areas, or rotational grazing.

PhD ceremony:    ir. R. van Klink
When:    June 20, 2014
Start:    14:30
Promotors:    prof. dr. J.P. (Jan P.) Bakker, M.F. wallis de Vries
Where:    Academy building RUG
Faculty:    Mathematics and Natural Sciences