Time since fire shapes vegetation structure and fuel availability in northern Patagonia

TIRIBELLI, F.; MORALES, J.M.; KITZBERGER, T.

Punta Arenas

Congreso; VIII Southern Connection Congress; 2016

Fire plays a key role shaping vegetation dynamics in many ecosystems worldwide. In northern Patagonia, fire has historically determined vegetation patterns and plant community composition. After a fire, shrubs rapidly dominate the post-fire community due to their resprouting capacity, while for obligate seeders treesit takes longer to regenerate into a forest. Fire frequency is higher in shrublands and fire tends to spread more readily than in forests. Thus, Patagonian forests and shrublands present different fire regimes,perhaps due to their different vegetation structure, species composition and time since fire. Consequently, there might be two alternative stable states dominating this landscape: one that burns frequently, possibly associated to more flammable vegetation (i.e. shrublands) and another that burns less frequently andmay be less flammable (i.e. forests). The aim of our study is to understand how vegetation structure changes with time since fire in Nothofagus dombeyi forests and Nothofagus antarctica shrublands. We found that shrublands? vegetation structure has characteristics that makes fire spread more likely inshrubs than in forests. In the latter, both vertical and horizontal vegetation continuity decreases with time while in shrublands it remains constant and higher. Moreover, fine fuel availability decreases in forests while it rapidly increases in shrublands. Hence, old forests would be fuel limited and discontinuous, while shrublands would not have fuel limitations and present vegetation continuity. Finally, we conclude that the opposite responses of their vegetation to time since fire found in this work could explain the distinct fireregimes of these two communities. (Sponsored by PIP 112 201101 00058 (to JMM))