Earthworms in the Haseldorfer Marsch

pictureIn the Nature Conservation Reserve (NSG) “Haseldorfer Binnenelbe” the breeding pewit population on the 141 ha grassland counted 24 pairs in 1994. In 2010 only 7 breeding pairs were present. As in spring already the development of territories is missing since several years, it was presumed that the high water levels during backwater periods cause a decline of the earthworm population. Earthworms are the favorite food of adult pewits. The hypothesis is that the long backwater period in spring may cause oxygen deficits in the soil that cause the decline of the earthworm population.

In the present project the earthworm density in three areas of the NSG “Haseldorfer Binnenelbe” is spatially investigated. Additionally to the earthworm density, the richness of life strategies and the biomass is studied. Furthermore, the pH of soil, the content of organic matter in soil, and the inundation level are considered as abiotic factors to develop a habitat model for a spatial display of densities and biomasses. The limits of backwater levels should be derived from this model. An area at “Beltringharder Koog”, where a relatively high breeding population of pewits still exists, is additionally investigated.