XI WORLD FORESTRY CONGRESS

Antalya, Turkey, 13 to 22 October 1997


VOLUME 2, TOPIC 9


    AFFORESTATION OF AGRICULTURAL LAND BY NATURAL FOREST COLONIZATION

    Christian Gauberville 1

    The observation of natural colonization of former agricultural land in central France has demonstrated that afforestation using economically valuable species is possible in certain circumstances.

    A bibliographic synthesis of the general principles of colonization of this land was used as a reference point to understand the field dynamics.

    Finally, the study of various soils and plants present could be used as an instrument for forecasting the probability of economically-valid natural forest colonization.

    Keywords: Agricultural land, natural afforestation, oaks, willow.

    1 Institut pour le Développement Forestier, 23 avenue Bosquet, F-75007 Paris, France.

    THE EFFECT OF FOREST EXPANSION ON RISES IN WATER LEVELS: NOTES ON SOME MOUNTAIN WATERSHEDS IN FRANCE

    Antoine Hurand 1

    How can we explain the effect of mountain forest expansion, which has been considerable over the last hundred years, on rises in water levels?

    The study of small experimental catchments (in the southern Alps and Massif Central) and models drawn from wider catchments (Pyrenees) underlines the importance of initial hydrological soil status and reveals the existence of a saturation effect. The mitigating effects of forest expansion are especially important on initial degradation, providing hydrological effects and helping to check erosion.

    While difficult to discern, increasing forest cover tends to have a stabilizing effect on water levels by reducing the scale of average rises. However, historical extremes in water level rises should be maintained as a reference point for land use planning, because threshold levels will have been exceeded irrespective of forest development.

    Keywords: Mountain forest, rises in water levels, hydrology, catchment area, model- making.

    1 Office National des Forêts, Service des Restauration des Terrains en Montagne, 23bis boulevard Bonrepos, 31000 Toulouse, France.



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