Diversity and functional groups dynamics affected by drought and fire in Patagonia grasslands.

GHERMANDI, LUCIANA & GONZALEZ, SOFÍA.

ECOSCIENCE (SAINTE-FOY)

UNIVERSITE LAVAL

Año: 2009 vol. 16 p. 408 - 417

1195-6860

In northwestern Patagonia in 1998-1999 a very severe drought occurred which decreased significantly the diversity and provoked a wildfire that burned wide areas of grassland. We monitored vegetation cover and seed bank during four years to study the diversity and species gap dynamics in burned and unburned grasslands. The vegetation recovered quickly post-drought due to rainy spring and summer 2000 and decreased after spring 2001 dry and warm. Also, temperature influenced vegetation dynamics and the low temperature in autumn and spring 2002 maintained low values of cover and seed bank. These patterns show a close relationship between phenophases and meteorological variables, which would became important in a climatic change context. The typical gap species Erophila verna showed coupled inter-annual patterns between cover and seed bank than can be explained by the “overcompensation” mechanism. Fugitive species were abundant in burned sites showing a possible fire dependency and the utilization of “storage effect” as coexistence mechanism. Diversity increased by the colonization of anemochorous species and fugitive species in unburned and burned sites. El Niño/Southern Oscillations phenomena are related to the occurrence of fires and drought in Patagonia and future changing environmental scenarios would be modelled to predict the reaction of plants.