Growth of male and female Araucaria araucana trees respond differently to regional mast events, creating sex-specific patterns in their tree-ring chronologies

Araucaria araucana is a dioecious evergreen conifer endemic from temperate forests of south Argentina and Chile. It is a long-lived species (maximum age > 1000 years), and it presents a high potential for tree-ring based climate reconstructions. However, the species’ dioecious habit can result in distinct sex-specific growth patterns, which introduce novel challenges in the interpretation of tree-ring chronology variations. We used a network of 10 tree-ring chronologies from northwest Patagonia (Argentina) to analyze sex-specific growth patterns in A. araucana and, for the first time, demonstrate that they result from the contrasting responses of ring width index of male (RWImale) and female (RWIfemale) trees to regional mast events (years with high seed production). During the year of seed maturation and seed dispersal, the growth of females was strongly and significantly reduced, while a growth response of similar magnitude was found in male trees in the previous year, corresponding to the year of pollination. We interpret these growth responses as representing contrasting allocation shifts between growth and reproduction in males and females. The sex-specific growth responses associated with mast events resulted in a particularly strong and distinct signal in a RWImale–RWIfemale chronology. Male and female tree-ring chronologies shared a strong common signal, and responded similarly (but not exactly) to broad-scale climatic conditions in the growing season. Our results indicate that sex-specific tree-ring chronologies can be used to isolate mast events in A. araucana chronologies, providing an opportunity to develop unique multi-century reconstructions of large mast events, and improve dendroclimatic calibration for this species.Fil: Hadad, Martín Ariel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Centro de Investigaciones de la Geosfera y Biosfera. Universidad Nacional de San Juan. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones de la Geosfera y Biosfera; ArgentinaFil: Roig Junent, Fidel Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina. Universidad Mayor; ChileFil: Arco Molina, Julieta Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; ArgentinaFil: Hacket Pain, Andrew. University of Liverpool; Reino Unid

Variations in the intrinsic water-use efficiency of north Patagonian forests under a present climate change scenario: tree age, site conditions and long-term environmental effects

The carbon isotope composition (δ13C) in tree rings were used to derive the intrinsic water-use efficiency (iWUE) of Araucaria araucana trees of northern Patagonia along a strong precipitation gradient. It is well known that climatic and ontogenetic factors affect growth performance of this species but little is known about their influence in the physiological responses, as iWUE. Thus, the main objective of this study was to assess the physiological reactions of young and adult trees from two open xeric and two moderately dense mesic A. araucana forests to the increases in atmospheric CO2 (Ca) and air temperature during the 20th century, and to relate these responses with radial tree growth. The results indicated that the iWUE and the intercellular CO2 concentration (Ci) increased 33% and 32% in average during the last century, respectively, but carbon isotope discrimination (∆13C) was more variable between sites and age classes. Trees from xeric sites presented greater iWUE and lower ∆13C and Ci values than those from mesic sites. In general, iWUE was strongly related with Ca and was significantly affected by mean summer maximum temperature. ∆13C from mesic sites seemed to be mainly affected by summer maximum temperature, while trees from xeric conditions did not show any influence. Tree age also presented a significant effect on iWUE. Adult trees showed higher iWUE values than young trees, indicating an incidence of the tree age and/or height, mainly in closed mesic forests. Moreover, some trees presented positive relationships between iWUE and radial tree growth, while others presented negative or no relationships, indicating that other factors may negatively influence tree growth. Broadly, the results demonstrate the incidence of climatic, environmental and ontogenetic variability in the tree responses; however, more studies are needed to better understand which forests will be more affected by actual and future climate changes.Fil: Arco Molina, Julieta Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; ArgentinaFil: Heller, G.. German Research Centre for Geosciences; AlemaniaFil: Hadad, Martín Ariel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Centro de Investigaciones de la Geosfera y Biosfera. Universidad Nacional de San Juan. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones de la Geosfera y Biosfera; ArgentinaFil: Roig Junent, Fidel Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentin