Large herbivores in coastal dune management: do grazers do what they are supposed to do?

After some decades of rather sparse and more or less ad-hoc nature management (e.g. local shrub-cutting, sod-cutting, mowing), the manager of the Flemish coastal nature reserves [Nature Department (Coastal Zone Management Cell) of AMINAL, Ministry of the Flemish Community] decided to introduce a more coherent and relatively large-scale nature management approach. Since the mid-nineties, several large areas were cleared from scrubs and in the larger nature reserves different herbivore species were introduced. On historical grounds and based on general management expectations, several ungulate species were introduced (sheep, donkeys and different horse and cattle breeds). Since the herbivore introductions from 1997 onwards, research has been done on the foraging behaviour and habitat use, diet selection and preference of some of the introduced herbivores and on their potential contribution to seed dispersal. Above that, several monitoring research programmes were carried out, following the impact of the ungulates on flora, vegetation and different faunal groups in order to evaluate the effectiveness of grazing in realizing the predefined management goals. Here we summarize some results of the research focussing on the driving forces in grazing management and try to conclude on the impact they will have through their habitat use, foraging behaviour, diet selection and other behavioural aspects. We formulate generalized conclusions on the suitability and usefulness of year round grazing by domestic animals in these rather low productive, spatially and temporally heterogeneous dune ecosystems

Germination success of temperate grassland species after passage through ungulate and rabbit guts

Dispersal of endozoochorous seed involves uptake by a herbivore and exposure to different kinds of digestive fluids during passage through the gastrointestinal tract. Assessment of the ecological significance of endozoochory therefore requires examination of the survival rate of seeds during this phase. A feeding experiment was conducted with seeds of 19 plant species that are important constituents of temperate semi-natural grasslands and five animal species (two ruminants, two colon fermenters and a caecum fermenter). Mean retention time of germinable seeds was determined and seed characteristics that might affect germination success were examined. Gut-passed seeds had a much lower germination success (0-26%) than non-gut-passed seeds either sown directly on dung (2-79%) or bare soil (7-89%). Relative germination success differed considerably between both plant and animal species. This may result from complex, herbivore-specific interactions between animal behaviour (chewing, digestion) and seed characteristics. Germination success was positively related to seed longevity and, remarkably, also to seed mass and seed shape. Retention time of germinable seeds varied from c. 12 hours (rabbit) to 72 hours (ungulates), potentially allowing long-distance seed dispersal. This study highlights both the complex interaction between animal species and seed characteristics and the considerable differences in germination success of gut-passed seeds, which exist between plant species. The loss of seed germinability after gut passage calls into question the ecological significance of endozoochory, although the costs of other dispersal mechanisms remain to be tested

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 specie

Donkeys as mobile links for plant seed dispersal in coastal dune ecosystems

Long-distance seed dispersal is a key factor in vegetation dynamics, especially in highly dynamic ecosystems such as dune landscapes. To assess the role of large herbivores in long-distance seed dispersal in dunes, we examined epi- and endozoochory by free-ranging donkeys, released for grazing in a Flemish dune nature reserve. At least 29, respectively 53, plant species were dispersed epi- and endozoochorously by the donkeys. Comparison of the species with the local vegetation using dispersal-relevant plant traits, showed that epi- and endozoochory are additive and complementary dispersal mechanisms, epizoochory being restricted to a narrower range of dispersal-functional plant types. To estimate potential dispersal distances of the seeds, we used empirical studies of the movement and behaviour of the donkeys, in combination with experimental epi- and endozoochorous seed retention times of selected plant species in the dune reserve. The mean potential dispersal distances indicated that the donkeys disperse seeds over the entire 100ha nature reserve, hereby providing a mobile link function between fragmented dune habitats for at least 20% of the local plant species. The influence of large herbivores on dune vegetation dynamics through seed dispersal should be considered in nature management decisions