CONICET | Buscador de Institutos y Recursos Humanos

It is widely accepted that forest decline is a complex phenomena involving diverse processes such as tree vigor loss, crown dieback, branch mortality, cambial disruption, and the consequent mortality of trees. Drought is one of the most important environmental factors predisposing forest decline. In Patagonia, forest decline has been reported since the second half of the last century. We related external tree-vigor characteristics with patterns of radial growth in Austrocedrus chilensis and Nothofagus pumilio forests in Patagonia, Argentina. In mesic A. chilensis forests visually affected by decline, the onset of radial growth differentiation between declining and non-declining trees was significantly related to negative PDSI anomalies during the year prior to growth. Furthermore, the radial-growth decline at the tree level was related to the occurrence of droughts and/or extended periods of unfavorable growth conditions. Similarly, different patterns of tree growth were observed at the stand and regional level on N. pumilio forests showing external evidences of tree decline. Whereas some trees show a steady reduction on tree growth, others increase radial growth after some decades of negative or uniform trends in growth. For the northern populations of N. pumilio, drought was the major factor determining these changes in tree-growth patterns. For southern Patagonia, the increase in temperature during the last decades appears to be the climate forcing related to forest decline. Based on future climatic predictions suggesting increasing trends in temperature and in the frequency and intensity of drought events in Patagonia, a gradual increase in the number of stands affected by decline along the twenty-first century is likely expected.