Consequences of dehesa management on tree-understorey interactions.

Moreno, G., Obrador, J., García, E., Cubera, E., Montero, MJ., Pulido, F. 1 Centro Universitario, Universidad de Extremadura, Plasencia 10600, Cáceres, Spain email: gmoreno@unex.es SUMMARY We have studied the distribution of resources (light, microclimate, soil moisture and soil nutrients) and fine roots (herbaceous plants and tree) around trees in four dehesas with three types of management: cropped (forage) grazed (native grasses) and encroached (matorral). Additionally, we have measured the forage yield and the physiological status, growth and acorn production of Holm-oaks. A low overlapping of the root systems of herbaceous plants and trees have been found, which could contributed to avoid competition. Soil water consumption by trees did not affect negatively to the forage productivity. Light interception by trees was limited to the close vicinity of the trees, with very low effect out of the canopy. On the other hand, both microclimate and soil fertility improved significantly in the vicinity of the trees, although only in less fertile soils contributed to increase forage yield. Dehesa management affected significantly to the physiological status, growth and productivity of trees.