Méthode Pragmatique d'Evaluation de la Réserve en eau des Stations Forestières et Cartographie à l'Echelle Régionale

Abstract

"Pragmatic assessment of the water reserve of the forest sites and mapping at the regional scale (Wallonia, Belgium). The assessment of the forest sites water availability constitutes a growing concern following the awareness of the potential impact of climate change on the soil moisture regime. At the present time, the forest managers lack tools for a quantitative estimation of the soil water reserve. This paper presents a simple estimation method that can be adopted on field by foresters. A map of this soil water reserve at the forest site scale has been established for the Southern Belgium. After the inventory of the possible techniques, the 'textural method', based on the pedotransfert classes of Jamagne et al. (1977), has been used. The soil profiles from the Aardewerk database have eased the translation of the Jamagne et al. (1977)'s results in the Belgian textural system. Moreover, the geodatabase of the Digital Soil Map of Wallonia (DSMW), through the typology of the major soil types, has been used as mapping support of the water reserve at the regional scale. Like a first attempt of validation, the result has been compared with the bioindicator character of forest understory vegetation. The regression results show a significant relationship between the soil water reserve and the vegetation estimate, but they also indicate that the water reserve does not explain alone the moisture level expressed by the flora. It emerges that the characterization of the Walloon parent materials will constitute an undeniable support for the development of the proposed method, the transposition of foreign results leading to some bias. The use prospects of this thematic map are multiple: integration as inputs for the autecological modelling, assessment of the moisture regime for the water availability of forest sites and building of sites catalogs; as many tools to guide forest managers in their planning measures."