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Tanguy Daufresne INRA-CEFS (dept. of wildlife behavior and ecology) Toulouse, France

US-France Young Engineering Scientists Symposium Washington, DC, October 22-24, 2007. Tanguy Daufresne INRA-CEFS (dept. of wildlife behavior and ecology) Toulouse, France. Biogeochemical signature of herbivores in terrestrial ecosystems T. Daufresne and J. Merlet.

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Tanguy Daufresne INRA-CEFS (dept. of wildlife behavior and ecology) Toulouse, France

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  1. US-France Young Engineering Scientists Symposium Washington, DC, October 22-24, 2007 Tanguy Daufresne INRA-CEFS (dept. of wildlife behavior and ecology) Toulouse, France Biogeochemical signature of herbivores in terrestrial ecosystems T. Daufresne and J. Merlet

  2. General research interests how chemical constraints influence strategies, interactions between species, and ecosystem functioning (“Ecological stoichiometry”) Research topic at CEFS The interaction between deer and forest biogeochemistry Influence of biogeochemistry on deer physiology Consequences for deer demography Influence of deer on forest biogeochemistry Consequences for plant community dynamics

  3. Biogeochemistry is critical for our understanding of ecosystem functioning (Odum 1969) and community dynamics (Tilman 1982) Nutrient ratios matter Herbivores can play a major role in biogeochemical cycles Zooplankton regulate N vs P availability (e. g., Andersen 1997) Ungulates can accelerate N cycling in savana (e. g., McNaughton 1992)

  4. The deer issue: a recent increase in ranges and densities Europe North America Capreolus Cervus Odoileus

  5. Virtually no forest in Europe and North america free from deer impact Red deer doe, Pyrénées, France Major impacts on understory structure and biodiversity, tree regeneration Understory of Pacific rainforest (BC) browsed by black-tailed deer Large-scale impact on biogeochemistry?

  6. * * * Looking for patterns: an experimental approach Creag Meagaidh Nature Reserve Northern atlantic birch forest, Peaty soil (Carline et al. 2005) P N:P UK Ge Fr Foliar N and P as a proxy for N and P availability Deer decrease N to P ratio Sp Gardouch Field Station Sub Mediterranean downy oak forest clayish limestone soil (Daufresne et al., in prep) * It P N:P * * *

  7. vegetationbiomass Looking for generic mechanisms: a minimalist Deer-vegetation-soil model foliar N foliar P Soil N Soil P Deer density increases - vegetation has less control over soil N -more leaching of soil N -decrease of total N -foliar N increases less dramatically than foliar P, hence, foliar N/P decreases As vegetation decreases due to browsing there is more available resource (N and P) for the remaining plants Deer density increases foliar P Foliar N:P foliar N

  8. Large scale Collaboration with forest ecologists and managers Europe North America The Renecofor Network ONF exclosures -deciduous -broadleaf evergreen -coniferous evergreen ? Pilot site (Gardouch, France) Collaboration with soil scientists Controlled deer density N, P inputs monitoring N, P, … monitoring in plants N,P, … in soil solution Inorg. / org. N in leachates

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