El papel facilitador o inhibidor de Pinus Pinea L. Sobre especies autóctonas de matorral mediterráneo

Abstract

Negative and positive interactions operate simultaneously in plant communities and the balance between these two forces drives community structure and function. Mediterranean sand dune ecosystems are nutrient-poor systems in which vegetation is composed mainly by Pinus pinea L., Juniperus phoenicea L., Osyris lanceolata Hochst. & Steud. and several shrubs belonging to the Cistaceae. P. pinea, due to its abundance and size, is known to interact with the rest of the species. With these assumptions we investigated the possible impacts of P. pinea on several aspects: (1) seed germination and seedling performance of three Mediterranean shrubs (Cistaceae family), (2) study of the decomposition processes of various life forms at the study site, (3) intensity of competition between seedlings of P. pinea, C. salvifolius and P. lentiscus under different combinations and nutrient treatments in order to evaluate the different behavior under nutrient-rich or poor conditions and (4) evaluate the special relationship between O. lanceolata, a hemiparasitic dioecious shrub and P. pinea. A thin needle layer could improve seed germination and seedling performance of shrub species due to the maintenance of a safe site and supplying some nutrients. These same needles may retard decomposition processes, but the presence of O. lanceolata litter in the soil enhances litter decomposition by releasing nutrients and enhancing litter decay rates of other species. A well-developed root system allows P. pinea to cope with the rest of the species and morphological traits are more important in predicting changes in competition than ecophysiological traits. This doctoral thesis highlights the important role played by O. lanceolata, not only in the nutrient cycling, but also spreading at the study site due to the presence of a good host, P. pinea.