Small-scale interactions between wind blowdown and avalanches shape Nothofagus forests in southern Patagonia

MARIANO AMOROSO; RICARDO VILLALBA; MARCOS RADINS; PAULA BLAZINA; MATIAS RUIZ; ANA M. SRUR

Melbourne

Conferencia; 9th International Conference on Dendrochronology; 2014

Past Global Changes (PAGES)

Wind blowdowns and avalanches are important disturbances affecting the temperate mountain forests of southern Patagonia. In previous research, we reported for the first time the occurrence of wave regeneration after wind blowdowns in continental Nothofagus pumilio forests. Furthermore, we identified the presence of avalanche channels and debris in several blowdown patches, but it is unknown how these two disturbances may interact.We undertook a retrospective study to date wind blowdown and avalanche events to studythe disturbance?s interaction and to reconstruct the overall forest structure and dynamics in Nothofagus pumilio forests in Santa Cruz, Argentina. We used (i) vegetation transects along the regenerating patches and adjacent undisturbed forests to reconstruct wind blowdown events, (ii) standard avalanche reconstruction methodology to date avalanche events, and (iii) transects along the entire study area to reconstruct overall forest structure and dynamics. Mortality and establishment dates, growth patterns, and scar dates were used in each case. The frequency and magnitude of wind blowdown events was highly variable. Pre-blowdown structure of the forest and wind intensity determined disturbance severity, leading to diverse post-blowdown structures in the regeneration patches. Avalanches followed blowdown events, but older events might have taken place as well. Their impact was larger at the highest elevation blowdown patches. The resulting stand structure exhibited a multimodal age distribution with many release events depicting the past multiple disturbance events. This study represents the first report of wind blowdownavalanche interaction for Nothofagus forests in Patagonia.