Heathlands functioning in a perspective of climate warming - Estimation ofparameters, elements for discrete event simulation

Three Calluna vulgaris (L.) Hull heathlands (1100, 1500 and 1780 m altitude ) are studied in order to establish and estimate parameters which will be i ntegrated in a discrete event simulation of heathland functioning in the ca se of a 2 degrees C climate warming. The sites, situated in the Chaine des Puys and the Massif du Sancy (France), present similar conditions for Callu na growth: bedrock (trachyt), exposure and slope, so that they can be compa red on a climatic basis. Main parameters sampled are: age distributions, li fe expectancies, layering probabilities, annual growths, biomasses (standin g crop), C/N rates and potential respiratory of soils. In addition, experim ents were carried out on germination, hypocotyle elongation and growth of m ycorrhizal fungi in order to estimate the inhibitory-to-growth action again st the substitution process. On one stand (exhibiting gaps) the patch struc ture of Calluna plants was recorded and mapped. The rising of biomass expec ted is calculated according to the Aerts's model, as a function of nitrogen availability which would increase under a scenario of climate warming. Fro m a similar point of view, layering probabilities, life expectancies and in hibition of seedlings survival modelling - under a linear model assumption - are proposed.