Document: REY-3-35-44

Interaction balance in shrub clusters in a Mediterranean semi-arid ecosystem.

LUQUE, M.T.*, R.TIRADO and F.I.PUGNAIRE

Estación Experimental de Zonas Aridas, CSIC, Almeria, Spain ¹

Abstract:
Communities of Maytenus senegalensis var. europeaus in semi-arid SE Spain are coastal ecosystems threatened for the pressure of intensive greenhouse agriculture. Many shrub, forb and annual species are clustered in patches where Maytenus is the focal plant. To analyze the structure of this community we studied the spatial pattern of species distribution and performed an experiment in which we factorially removed individuals of the three main shrub species in order to identify the mechanisms of interaction by comparing isolated individuals and individuals growing in the community. We followed growth and water status of the target plants for one year. The results showed strong associations among the species in this community. Shrubs like Whitania frutescens and Rhamnus lycioides had higher growth rate and higher water potentials living in communities than isolated, while Maytenus senegalensis had lower growth rate but higher water potentials in communities. Facilitation and competition appear to act simultaneously in these clusters of shrubs, where the net balance seems to be positive for all interacting species due to harsh environmental conditions and high herbivore pressure.

Keywords: spatial pattern, facilitation, competition

This abstract is being presented at: 10:30 AM in session:
PLANT DEMOGRAPHY