CONICET | Buscador de Institutos y Recursos Humanos

The mortality of the Austrocedrus chilensis forests, locally known as Mal del Ciprés, has been reported since 1945 in most sites across the species distribution in Argentina. However, the cause of this decline is still a topic of discussion. In this study, radial growth patterns from symptomatic and asymptomatic A.chilensis trees were analyzed in relation to registered climatic events near El Bolsón town, Río Negro province, Patagonia, Argentina. Five pure A.chilensis stands were selected, in which 10 pairs of symptomatic and asymptomatic trees were bored which were similar in DBH, competition, and microsite conditions. A chronology of reference was developed in order to crossdate all the material and to evaluate the relationship between A. chilensis and climate in the study area. The radial growth of A. chilensis in this area was found to be favored by above-average precipitation in late spring - early summer (November and December). A strong relationship was observed between radial growth patterns and the Palmer Drought Severity Index (PDSI), a measure of the regional water deficit. The Principal Component Analysis showed that drought events registered in the area are distinguishable as small tree rings both in symptomatic and asymptomatic trees. Significant differences in growth patterns were found between symptomatic and asymptomatic trees. When annual growth from symptomatic trees starts to be consistently lower than that from asymptomatic trees, a significant relation was found to extreme drought events occurred the previous year. Based on tendency of droughts during the last 50 years and on future predictions of more frequent and intense drought events in northern Patagonia, a gradual increase in A. chilensis stands affected by this decline is highly expected along the XXI century.