Gradient Analysis of Exotic Species in Pinus radiata Stands of Tenerife (Canary Islands)

Identifying the factors that influence the spread of exotic species is essential for evaluating the present and future extent of plant invasions and for the development of eradication programs. We randomly established a network of 250 plots on an exotic Pinus radiata D. Don plantation on Tenerife Island in order to determine if roads and urban centers are favouring the spread of exotic plant species into the forest. We identified four distinct vegetation groups in the P. radiata stands: advanced laurel forest (ALF), undeveloped laurel forest (ULF), ruderal (RU), and Canarian pine stand (CPS). The groups farthest from roads and urban nuclei (ALF and CPS) have the best conserved vegetation, characterizing by the main species of the potential vegetation of the area and almost no exotic and ruderal species. On the other hand, the groups nearest to human infrastructures (ULF and RU) are characterized by species from potential vegetation’s substitution stages and a higher proportion of exotic and ruderal species. The results indicate distance to roads and urban areas are disturbance factors favouring the presence of exotic and ruderal species into the P. radiata plantation. We propose the eradication of some dangerous exotic species, monitoring of the study area in order to detect any intrusion of alien species in the best conserved areas and implementation of management activities to reduce the perturbation of the ULF and RU areas.