ANDREAS ROTH, FRANK GRESENS, HEINER GOLDBACH, JÜRGEN BURKHARDT
University of Bonn, Institut of Plant Nutrition, Germany
Southern Morocco is a semiarid, heavily grassed region with a long tradition of transhumance activity. The spatial ecosystem model SAVANNA, developed by M. COUGHENOUR, is being used to model ecosystem dynamics and to gain knowledge about the thresholds of sustainable use in this region. Within SAVANNA different functional groups of vegetation are defined to simulate plant growth and plant competition for nutrients and water. In addition, biomass intake by animals and the movement of herds are simulated.
Parameterisation and calibration of the SAVANNA model for the Draa watershed as well as first simulation results will be presented, considering sheep, goats and camels as the most abundant animals. For the plant part of SAVANNA, transpiration measurements as well as biomass determination are being used, which were carried out in the years 2001-2003 in order to achieve an estimate of the plant influence on the hydrological circle of this water catchment. Intensive measurements took place in a characteristic rangeland area of the nothern Draa valley at Taoujgalt (1900m a.s.l.), located at the southern slope of the High Atlas mountains with a homogeneous plant cover. The dominant perennial species are Artemisia herba-alba and Teucrium mideltense.
Biomass production and plant transpiration in this region are less linked to local precipitation, and may even exceed precipitation. This indicates the influence of local water storage in the soil, and/or the influence of groundwater fluxes within this mountainous region. As well it is important to comprise that the groundwater level of this area strongly depended on local precipitation, due to the well irrigation systems of farmers in the nothern part of Taoujgalt area.
Keywords: Biomass, desert, plant modelling, precipitation, south Morocco, transpiration rates, water use