Tanguy Daufresne INRA Toulouse Laboratoire de Comportement et

Tanguy Daufresne INRA Toulouse Laboratoire de Comportement et Ecologie de la Faune Sauvage (Behaviour and Ecology of Wildlife) Coupling deer and forest models in capsis: why and how?

Roe deer Capreolus capreolus Red deer Cervus elaphus medium size ungulate (20 -30 kg) Low sexual dimorphism generalist selective browser Territorial Large size ungulate (80 -300 kg) High sexual dimorphism Generalist selective browser/grazer Social

In France overall deer populations (both roe and red) have dramatically increased over the past three decades, due to local density increases and re -colonization. Data are from ONCFS

In 2000 red deer were present on 39 % of the woody areas in continental France (+Corsica). and 50 % of the total red deer population occupied 10 % of the wooded areas. Data are from ONCFS

Data are from ONCFS

Deer effects on forest dynamics (Rooney et al. 2003): Direct effects by selective browsing: -understory density and diversity -tree regeneration Indirect effects: -mediation of plant-herbivore interactions -mediation of plant-plant interactions -altered nutrient recycling Forest effects on Deer dynamics: Habitat quality: -transfert of soil fertility to foliage quality -understory density -hedge effect

Species richness Impact of black-tailed deer (Odocoileus hemionus) on forest understory in Western British Columbia (Stockton et al 2005) Biomass density

Impact of black-tailed deer (Odocoileus hemionus) on population structure of an understory shrub, the red huckelberry (Vaccinium parvifolium) in Western British Columbia (Vila et al 2004)

Indirect effects of deer on vegetation -Deer affect patterns of dominant species in understory and canopy through selective browsing (Rooney and Waller 1994). -Deer browsing affects community dynamics of vegetarian insects by reducing host plant densities (Baines et al. 1994). -Deer affect nutrient status of saplings through differential recycling of nitrogen versus phosphorus (Carline et al. 2005), and nutrient transfer from cultivated land to woodland (Seagle 2003).

Feed-back effects of forest structure on deer population dynamics -Reduction of understory biomass due to change in fire regime entailed decline of mule deer in Oregon (Peek et al. 2001). -Soil fertility influences foliage quality, hence body size in roe deer (Petorelli et al. 2001).

Impact of red and roe deer on forest succession in Europe -Gap models with a negative “deer effect” on recruitment + + seedling small sapling large sapling deer -Predictions are model and site specific ex: Pine land evolving towards birch-oak stand (Jorritsma et al. 1999) -roe deer eliminate the oak and succession tends to pure birch stand -red deer tends to slow down the succession process and promote pineland over birch-oak forest Spruce evolving towards pine stand (Kienast et al. 1999) -ungulate does not affect succession pattern but affects forest structure by accelerating the maturation cycle and reducing the density of trees.

Caveats : -Models do not detail enough the early stages of the life cycle of trees -Indirect effects of deer on trees are ignored -Feed-backs of forest structure on deer population dynamics are ignored

seedling small sapling light nutrient large sapling deer Taxon abundance undersory deer density (After Rooney and Waller 2003)

Perspectives 1 - Theoretical “toy models”: - mediation tree-understory: deer population + understory +one species of canopy tree -stoichiometric model of N and P: soil nutrient+ deer population+understory 2 - introducing “deer effects” (including indirect effects) in forest models. 3 - creating a deer population model in capsis.