Sam Provoost

Ecology, management and monitoring of grey dunes in Flanders

Grey dunes are a priority habitat type of the European Union Habitats Directive and demand special attention for conservation and management. Knowledge of the ecology of coastal grey dunes can contribute to this policy. Dune grassland succession is initiated by fixation and driven by the complex of soil formation (humus accumulation) and vegetation development. Leaching and mobilization of CaCO3. which are important in nutrient dynamics, complicate the picture. At present, grass- and scrub encroachment greatly overrules these fine scaled soil processes and causes substantial loss of regional biodiversity. Belgium has an international responsibility in grey dune conservation because of the limited range of its characteristic vegetation, flora and fauna. As biomass removal seems essential in grassland preservation, grazing is an important management tool. Evaluation of management measures focuses on biodiversity measurements on the levels of landscape, community and species.

Microgeographical distribution of ants (Hymenoptera: Formicidae) in coastal dune grassland and their relation to the soil structure and vegetation

In this paper, we investigate the microgeographical distribution of ants nests in an intensively grazed dune pasture. A total of seven species were recorded. By the application of a forward multiple logistic regression we were able to determine nesting choice for the three common species Lasius niger, L. psammophilus and Myrmica specioides . The e rst could be identie ed as a pioneer species, while the two latter species, which are typical of dry, sandy dune grounds, differ slightly in their nesting preference. The effect of nest building on soil structure was investigated for a mound-building species ( Formica cunicularia) and for a non-mound-building species ( Lasius psammophilus ). Both species signie cantly decrease the thickness of the organic and water-capturing soil layer, while the mound-building species additionally affects the soil lime content (an increase) and the soil hardness (a decrease). Mound building in dense Calamagrostis vegetation also stimulates the germination of a characteristic and rare plant species, Thymus pulegioides .

Herbivore-induced expansion of Helianthemum nummularium in grassland–scrub mosaic vegetation: circumstantial evidence for zoochory and indirect grazing impact

Extensive grazing often has a strong influence on the structure and composition of herbaceous plant communities with increasing population sizes for some species and decreasing presence in others. Herbivores affect plant communities directly by selective grazing of plant species, and indirectly by either epizoochory or endozoochory. Helianthemum nummularium is considered an increasing species because its distribution increased after the introduction of large, free-ranging grazers in at least two coastal dune grassland areas in Belgium. However, its seeds lack any obvious adaptations for epizoochory, and direct observations of plant/seed consumption are scarce. Through field and lab experiments, we assessed the dispersal ability of H. nummularium via endozoochory and epizoochory. In a differentiated grazer exclusion experiment, evidence was found that plants are grazed by large domestic ungulates and small wild herbivores although these incidences were rare. Direct endozoochory evidence remained scarce. No seeds were found germinating in field-collected dung, and only few seedlings emerged following a seed feeding experiment. However, once deposited, we found higher growth rates when seeds were mixed with dung and decreased establishment success when seeds were sown in combination with competitively superior species. Epizoochory was plausible because both fur and hooves of cattle and horses were potentially capable of contributing to the transport of H. nummularium seeds. We conclude that herbivores play a role in seed dispersal, while their selective grazing behaviour most probably creates an appropriate environment for Helianthemum establishment and maintenance.