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Grazing the dunes

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Dynamic Dunes Congress 2015
Workshop: Grazing the dunes - Hubert Kivit

Published in: Environment
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Grazing the dunes

  1. 1. Grazing: What about the fauna? What do we learn from recent ‘Living Dunes’ (LD) & OBN research?
  2. 2. Methods • OBN: 24 dune areas – 113 locations with paired plots (grazed-ungrazed) • LD: 3 dune areas drinking water companies
  3. 3. Studied effects of grazing on animals • food – soil fauna – butterflies – plant quality for insects and rabbits – flower abundance – invertebrates as food (for e.g. birds) • nesting – sand nesting insects – habitat for breeding birds • thermoregulation – insects – sand lizard
  4. 4. Main effects of grazing on vegetation of grey dunes biomass standing crop decreases litter decreases grasses decrease herbs unchanged
  5. 5. Food: soil fauna • Strong decrease of detritivores (earth worms, millipedes, wood lice) • Contradictory results for herbivores & carnivores • NHD: increase in detritivores (LD) !
  6. 6. Food: butterflies Year round horse + cattle Summer cattle other Pyrgus malvae -- Coenonympha pamphilus -- -- Issoria lathonia ++ Maniola jurtina ++ ++ ++ Argynnis niobe ++ ++ ++ Lycaena phleas ++ ++ ++ Anthocharis cardamines -- Thymelicus lineola -- -- Pararge aegeria ++ Ochlodes faunus -- -- -- Favonius quercus ++ Aglais urticae -- -- -- Aphantopus hyperantus -- -- -- Many species show no effects ++ species of meagre vegetation or small-leaved grasses -- species of rough vegetation or broad-leaved grasses Effects partly caused by direct grazing on host plants
  7. 7. Food: plant quality for insects and rabbits Positive!
  8. 8. Food: plant quality for insects and rabbits No better plant quality!
  9. 9. Food: flower abundance Grazing increases flower abundance in R slightly High grazing pressure in W decreases flower abundance
  10. 10. Food: soil invertebrates as food • Density decrease of all size classes under grazing • Effect stronger at high grazing pressure • NHD: increase soil invertebrates (LD) ! Size class Significance Renodunal Wadden > 1.5 cm negative n.s. 0.5 – 1.5 cm negative negative < 0.5 cm negative negative
  11. 11. Nesting: sand nesting insects 75% reduction of nests in grazed sand patches more thermophilous insects on terracettes than on ungrazed slopes
  12. 12. Nesting: habitat alteration for breeding birds Positive Neutral Negative Open dunes 0 5 3 Low shrub 4 1 4 High shrub 1 4 9
  13. 13. Thermoregulation: insects Larger differentiation in microclimate in W at high grazing pressure decrease of microclimate diversity
  14. 14. thermoregulation: sand lizard • Contrary to inland situation no effects of grazing on trend in numbers
  15. 15. Conclusions Effect of grazing Soil fauna abundance --? Thermophilous invertebrates ++/- Nectar & pollen 0 birds -- Rabbits ++ Butterflies + Sand lizard 0 Effects of grazing on fauna highly dependent on • species/species group • grazing conditions • dune zone Much is still unknown!
  16. 16. Statement in a dynamic dune system grazing by livestock needs to be dynamic as well!

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