Study of a Natural Leguminous Plants/Cork Oak Association in Kroumirie: An Alternative Solution to Climate Change

Despite the increase of the atmospheric CO2, cork oak (Quercus suber L.) forests don’t stop degenerating. Deficits in water balance and in nutritional elements might be the main raisons. Standing as a potential regulator of the ecosystem nutrient dynamics, leguminous plants (Fabaceae, Leguminosae) are a good test case for individual species effects on Tunisian forests. They are the most diverse and widespread group of plants with the capacity of N2 fixation, and are particularly abundant in Kroumiri forests. The use of natural legume species in Kroumirie, as soil fertility and grassland productivity enhancer, could be very interesting in the assessment of a new national land exploitation strategy aiming to increase carbon sequestration and climate change mitigation. Understanding the impact of these legume species on cork oak, using air nitrogen-fixation technique computation, would be crucial for future land management and policy decisions. A morphological and eco-physiological study of the Cytisus triflorus plant associated with Cork oak was carried out in Tabbouba, at Nefza region. Three sites were selected: CM1 (Cytisus triflorus alone), CM2 (Cork oak associated with Cytisus triflorus) and CM3 (Cork oak only). Morphological (height, diameter, density), physiological (stomatal conductance, water potential, transpiration, photosynthesis) and hydric parameters were measured for the two species. The morphological study results showed no significant difference sites for each species except for density parameter. On the other hand, physiological parameters measured for oaks trees clearly manifested significant differences in photosynthesis, transpiration and hydric conductance between CM2 and CM3 sites. The cork oak in association with the Cytisus are in better growth and productivity conditions than when they are alone.