Revista Chilena de Historia Natural 77 (3): 455-464, 2004
RESEARCH ARTICLE
Fire regimes and vegetation responses in two Mediterranean-climate
regions
Wildfires resulting from thunderstorms are common in some Mediterranean-climate
regions, such as southern California, and have played an important role in the ecology and evolution of the flora. Mediterranean-climate
regions are major centers for human population and thus anthropogenic impacts on fire regimes may have important consequences
on these plant formations. However, changes in fire regimes may have different impacts on Mediterranean type-ecosystems depending
on the capability of plants to respond to such perturbations. Therefore, we compare here fire regimes and vegetation responses of two
Mediterranean-climate regions which differ in wildfire regimes and history of human occupation, the central zone of Chile (matorral)
and the southern area of California in United States (chaparral). In Chile almost all fires result from anthropogenic activities, whereas
lightning fires resulting from thunderstorms are frequent in California. In both regions fires are more frequent in summer, due to high
accumulation of dry plant biomass for ignition. Humans have markedly increased fires frequency both in the matorral and chaparral, but
extent of burned areas has remained unaltered, probably due to better fire suppression actions and a decline in the built-up of dry plant
fuel associated to increased landscape fragmentation with less flammable agricultural and urban developments. As expected, post-fire
plant regeneration responses differs between the matorral and chaparral due to differences in the importance of wildfires as a natural
evolutionary force in the system. Plants from the chaparral show a broader range of post fire regeneration responses than the matorral,
from basal resprouting, to lignotuber resprouting, and to fire-stimulated germination and flowering with fire-specific clues such as heat
shock, chemicals from smoke or charred wood. Plants from the matorral have some resprouting capabilities after fire, but these
probably evolved from other environmental pressures, such as severe and long summer droughts, herbivory, and volcanism. Although
both Mediterranean-type ecosystems have shown to be resilient to anthropogenic fires, increasing fire frequency may be an important
factor that needs to be considered as it may result in strong negative effects on plant successional trends and on plant
diversity.
Key words:
human impacts, plant
regeneration, matorral, chaparral
