Exotic dominance of ruderal communities depends on disturbance type

CHIUFFO, MARIANA; HIERRO, J. L.

Antalya

Conferencia; NEOBIOTA 2014 - 8th European Conference on Biological Invasions: "Biological Invasion, from understanding to action"; 2014

Çanakkale Onsekiz Mart University on behalf of NEOBIOTA ? The European Group on Biological Invasions, and in cooperation with other organisations

Disturbance commonly promotes the dominance of communities by exotic plants. Given that exotics are mostly ruderals (i.e., plants adapted to disturbed conditions), it is not surprising that they thrive in disturbed sites. Moreover, according to Grime?s plant strategy theory, exotic ruderals should overcome native plant species with alternative strategies, such as competitive and stress tolerant, in sites altered by disturbance. It is not clear, however, what would be the outcome of exotic ruderals versus native ruderals in these sites, as well as the role of different disturbance types in the outcome and ultimately in the invasion process. In the current work, we studied the response of exotic and native ruderal species to different types of disturbance in a system with a diverse community of native ruderals, the semi-arid open forest of central Argentina. We conducted extensive plant surveys in sites altered by the three main disturbances in the region, road maintenance (a combination of plowing and mowing with no herbicide applications), fire, and grazing by domestic herbivores to estimate relative abundance of exotic and native ruderals in these sites. In addition, we examined how disturbance type affected resource availability by measuring soil moisture. The richness of exotic ruderals was consistently lower than that of native ruderals in all three disturbance types. Also, the cover of the exotics was lower than that of native ruderals in sites disturbed by grazing and fire. In contrast, the cover of exotic ruderal plants was two times greater than the cover of native ruderals in sites disturbed by road maintenance. Soil moisture was also greater in road maintenance sites than in sites altered by the other disturbance types. These results suggest that exotics overcome natives only under disturbances that profoundly disrupt plant communities and highly increase resource availability.