Tree-ring evidences of insect outbreaks in Nothofagus pumilio forests in southern Patagonia, Argentina

MARIANO S. MORALES; MISAEL PALACIOS; ANA M. SRUR; ALIENOR LAVERGNE; MILAGROS RODRÍGUEZ CATÓN; SILVIA DELGADO; IGNACIO A. MUNDO; MARIANO AMOROSO; RICARDO VILLALBA

Tucson

Conferencia; Second American Dendrochronology Conference; 2013

University of Arizona

Insect outbreaks from Ormiscodes anphimone are easily recognized in the Patagonian landscape due to changes in color of Nothofagus pumilio forests in response to strong tree defoliation. In this study we use 26 N. pumilio tree-ring chronologies along a S-N transect from El Chaltén (49º25’S) to Laguna del Desierto (49º00’S) in southern Patagonia to reconstruct past Ormiscodes outbreaks over the period 1743-2010. In addition, we asses the relationships between outbreaks, climate variability and atmospheric circulation index including the Southern Annular Mode (SAM). Using dendroecological methods, 47 Ormiscodes outbreaks were identified over the period 1743-2010. Tree-ring chronologies from forests affected by Ormiscodes showed abrupt growth reductions during the years following the insect attacks. No periodicities were detected in the outbreak reconstruction. Although the relationships between outbreaks and climate variations seem to be complex, insect outbreaks appear to be related to drier climatic conditions and the positive phase of the SAM.