Revista Chilena de Historia Natural 77 (3): 465-483, 2004
RESEARCH ARTICLE
Exotic plant invasions to the mediterranean region of Chile: causes, history and
impacts
We review the literature on patterns, causes, processes and impacts of exotic plants,
primarily in the mediterranean region of Chile, considering three major non-independent drivers of the invasion process: (a) Availability
of exotic species propagules, (b) attributes of the local communities in which exotic species establish and through which they will
eventually spread out, and (c) attributes of exotic species that either facilitate or constraint their spread into new sites. Regarding
availability of propagules, central Chile matorral presents the communities with the greatest incidence of naturalized herbs, followed by
the sclerophyllous forest and the espinal scrubland in the coastal range. In contrast, north central communities have lower numbers
and proportions of naturalized species of herbs in their seed banks. Availability and persistence of naturalized herbs do not differ
between aboveground vegetation and seed bank. Regarding attributes of local communities associated with the establishment and the
spread of exotics, grazing regime and land use emerge as the most prominent causes that render them more prone to invasion by
exotics. Evidence on the effect of the fire regime is contradictory and native species richness does not seem to be an important factor.
Regarding attributes of exotic species seeds, results suggest that naturalized annuals germinate within a wide temperature range, are
highly resistant to cold and dry conditions, and show some degree of physiological dormancy. Additionally, naturalized annuals are
highly tolerant to poor soils, but are generally intolerant to shade. These general attributes have largely determined the invasion process
in the mediterranean region of Chile. Historical data indicate that an important number of exotic species were intentionally introduced,
and that the spread of exotic is uncontrolled. It has been demonstrated that arrival time of exotics is of great relevance to understand
present day spread of exotics in Chile, independent of their biogeographic origin. Exotic species may cause strong disruptions of
ecosystem processes and functions in Chile, as exemplified by exotic tree plantations, which have altered soil chemistry, nutrient
cycling, water cycle, hydrology, microclimate, and fire frequency and intensity.
Key words:
exotic species, plant
invasions, naturalized plants, invasion history, ecosystem disruption
