Wind blowdown history in Nothofagus forests in southern Patagonia

AMOROSO, MARIANO; RADINS, MARCOS; VILLALBA, RICARDO; RUIZ, MATIAS

Conferencia; Third American Dendrochronology Conference ? AmeriDendro2016; 2016

Wind is one of the most important disturbances affecting the temperate mountain forests of southern Patagonia. Wind blowdown history has been studied in Nothofagus pumilioforests in the southern island of Tierra del Fuego, and recent interest have been put on wind blowdowns leading to wave regeneration in continental forests; yet, little is known about the history (dates of origin) of this disturbance at a regional scale. We undertook a retrospective study to reconstruct and date wind blowdown events in five continental valleys of Santa Cruz, Argentina to reconstruct the blowdown history of N. pumilioforests. We used vegetation transects along the disturbed patches and adjacent undisturbed forests to i) reconstruct forest structure and dynamics, and ii) date mortality and growth releases events, and thus date the occurrence of windstorms; intense sampling along the edge allowed us to describe mortality and growth patterns in the residual trees after the windstorms. The occurrence of wind blowdown events was highly variable in the sampled valleys, and thus the resulting forest structure of the blowdown patches. The forests exhibited numerous growth release events depicting past multiple disturbance events and the frequency and magnitude varied at each valley. We determined a total of sixteen blowdown events, and the number of events per valley varied from two to six. Three events were recorded in more than one valley. Pre-blowdown structure of the forests and wind intensity might have determined disturbance frequency and severity, leading to diverse post-blowdown structures and blowdown history. This study represents the first reconstruction of wind blowdown history leading to wave regeneration in continental and mountain N. pumilio forests in southern Patagonia.