Species-specific influence of hydroclimate on secondary growth of three coexisting conifers in a temperate Andean forest in south-central Chile

Abstract

There is limited knowledge on the growth responses of coexisting conifer species to water conditions in the Andean region of South America- particularly in South-Central Chile (37°−40°S) where high temperatures and drought risk is expected to increase in the future. Here, we used wood cores from living trees and cross-sections of stumps to study the secondary growth responses to hydroclimatic environmental variables in Araucaria araucana, Austrocedrus chilensis and Prumnopitys andina, three coexisting conifers in a temperate Andean forest. The standardized tree-ring chronologies are robust and have been well replicated over the past two centuries, with an expressed population signal greater than 0.90. Our findings indicate that chronologies of Austrocedrus and Prumnopitys were quite similar, while Araucaria was almost independent. The secondary growth of Araucaria was negatively related to August precipitation and river runoff, likely due to a high probability of snow cover at high elevations in winter. In contrast, the secondary growth of Austrocedrus and Prumnopitys was positively associated with precipitation and streamflow and negatively with high maximum temperatures in two seasons, summer (December to February) and autumn (April to May). Prumnopitys growth was strongly associated with streamflow during last year´s and current year´s growing seasons. In the years 1962, 1998 and 2008 there occurred severe droughts, which were associated with growth reductions in the three conifers. Araucaria growth showed the greatest resistance to drought, while Austrocedrus was the most resilient to drought and showed the greatest ability for growth recovery after a drought. Araucaria growth showed near-constant resistance, recovery and resilience to drought during the study period, while Austrocedrus growth showed high recovery and resilience after the 1962 and 2008 droughts. Our results revealed contrasting behavior of coexisting conifers with respect to hydroclimate, which could help predict future changes in the performance of temperate Andean forests in a potentially drier and warmer climate.