Non linear ecological processes, fires, environmental heterogeneity and shrub invasion in NW Patagonia, Argentina L. Ghermandi

GHERMANDI L.; FRANZESE J.; GONZALEZ S.; DE TORRES CURTH M.

Congreso; EGU General Assembly 2008; 2008

The behaviour of emergent nature is not only the sum of interactions among ecosystemparts but it depends also on the organization of these interactions. Fire behaviour,climate and vegetation patterns produce non linear fire propagation across landscape.Fires can increase the abundance of determined species modifying the fire regime andincreasing the invasion of the same species (Fabiana imbricata and Senecio bracteolatusshrubs in NW Patagonia). Environmental heterogeneity, like the presence ofoutcrop, favours landscape patchiness with different fire frequencies and generates occupationof fire refuges by species that can survive there (Autrocedrus chilensis tree).We monitored shrub cover and recruitment during 8 postfire years in NW Patagoniagrasslands. We described shrub population dynamics with matrix models projectingthe population in hypothetical scenarios of different fires and ENSO (El Niño SouthernOscillation) frequencies. Fire promote shrub invasion in NW Patagonia. Globalclimate chance suggests the increase of frequency and amplitude of ENSO phenomena,which in NW Patagonia implies more coupled fires and rainy springs, and consequentlymore shrub windows of recruitment. The matrix models indicate that thisscenario promotes shrub invasion. Future satellite images and aerial photographs analysiswill provide information about long term changes in vegetation and fire regime.Our results improve the knowledge of ecosystem properties and processes providinguseful information for grassland sustainable use.