Tree-ring isotopes from Araucaria araucana as useful proxies for climate reconstructions |
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| Affiliation: | 1. Laboratoire des sciences du climat et de l''environnement (LSCE), Université Paris-Saclay, CNRS, CEA, UVSQ, Orme de Merisiers, 91191 Gif-sur-Yvette, France;2. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales (IANIGLA), CONICET, Av. Ruiz Leal s/n Parque General San Martín, Mendoza, Argentina;3. Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Cuyo, Padre Contreras 1300, Mendoza, Argentina;4. Tree-Ring Laboratory, Lamont-Doherty Earth Observatory of Columbia University, 61 Route 9 W, Palisades, NY 10964, USA;5. CREAF, Bellaterra (Cerdanyola del Vall.s), Barcelona, Spain;6. ICREA, Pg. Llu.s Companys 23, Barcelona, Spain;1. State key laboratory of vegetation and environmental change, Institute of Botany, Chinese Academy of Sciences, Xiangshan, Haidian District, Beijing 100093, China;2. University of the Chinese Academy of Sciences, Beijing, China;3. Linzhou Bureau of Meteorology, Linzhou, Lhasa, Tibet, China;4. Tibet Agricultural and Animal Husbandry University, Tibet, Linzhi, China;1. University of Fribourg, Department of Geosciences, Switzerland;2. University of Zurich, Department of Geography, Switzerland;3. Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY, USA;4. Institute of Earth Sciences, Hebrew University of Jerusalem, Jerusalem, Israel;5. Northern Arizona University, School of Earth and Sustainability, Flagstaff, AZ, USA;6. Institute of Geography and Oeschger Centre for Climate Change Research, University of Bern, Switzerland;1. Department of Geography, Environment and Geomatics, University of Guelph, 50 Stone Rd. E., Guelph ON, N1G 2W1, Canada;2. Universidad Nacional de Río Negro, Instituto de Investigaciones en Recursos Naturales, Agroecología y Desarrollo Rural (IRNAD), EL Bolsón 8430, Argentina;3. Consejo Nacional de Investigaciones Científicas y Técnicas, Instituto de Investigaciones en Recursos Naturales, Agroecología y Desarrollo Rural (IRNAD), EL Bolsón 8430, Argentina;4. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales, CCT CONICET, Mendoza 5500 Argentina;5. Instituto Nacional de Tecnología Agropecuaria (INTA), San Carlos de Bariloche 8400, Argentina;1. The State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi’an 710061, China;2. The University of the Chinese Academy of Sciences, Beijing 100049, China;3. Qingdao National Laboratory for Marine Science and Technology, Qingdao 266237, China;4. CAS Center for Excellence in Quaternary Science and Global Change, Xi’an 710061, China;5. Department of Earth and Environmental Science, School of Human Settlements and Civil Engineering, Xi’an Jiaotong University, Xi’an 710049, China;6. Shaanxi Appraisal Center for Environmental Engineering, Xi’an 710065, China;7. Beijing Municipal Weather Forecast Center, Beijing 100089, China;1. Key Laboratory of Cenozoic Geology and Environment, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, 100029, China;2. College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China;3. Center for Ecological Research, Northeast Forestry University, Harbin, Heilongjiang, 150040, China;4. CAS Center for Excellence in Life and Paleoenvironment, Beijing, 100044, China |
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| Abstract: | Tree-ring width (TRW) chronologies have been widely and long-time used to reconstruct past climate variations in the Andes in South America. The use of tree-ring isotopic chronologies is still not widespread in this region although they have proved to be very efficient climate proxies. Araucaria araucana (Molina) K. Koch is a conifer tree species with some multi-century-old individuals that offers an excellent opportunity to measure stable carbon (δ13C) and oxygen (δ18O) isotopes in cellulose from long tree-ring records. Here, we explore whether current or stored carbohydrates are used for A. araucana radial growth and we assess the potential of a tree-ring isotopic record of to study past climate variability. Eleven A. araucana cores from a dry and high-elevation forest at the northern border of Patagonia, Argentina (38°55’S, 70°44’W) were selected for stable isotopes analyses. The strong correlation between the isotopic composition of the first and second parts of the same ring, but also the strong relationships between δ13C and δ18O records with climate parameters of the current growing season such as temperature, show that tree-rings are built mostly with carbohydrates produced during the current growing season with little or no supply from storage or reserves. This finding leads to reconsidering the interpretation of the legacy effect (i.e. ecological memory effects) based on the previously described strong negative correlation between A. araucana TRW chronologies and previous growing season temperature and suggests a dependence of radial tree growth on the level of development of organs. Regarding climate sensitivity, the A. araucana tree-ring δ13C chronology is strongly related to current summer temperature (r = 0.82, p < 0.001), vapour pressure deficit (VPD; r = 0.79, p < 0.001), precipitation (r = −0.53, p < 0.001) and SPEI2 (r = −0.73, p < 0.001). These strong relationships support the use of δ13C of A. araucana tree-ring cellulose to reconstruct past temperature variations at regional scale in relation with large-atmospheric drivers of climate variability such as the Southern Annular Mode. The A. araucana tree-ring δ18O chronology is also correlated with temperature (r = 0.42, p < 0.01) and VPD (r = 0.45, p < 0.01) of the winter preceding the growing season. This suggests that trees are using water from precipitation infiltrated in the soil during the previous recharge period (autumn-winter). The weak correlations of δ18O with current summer atmospheric conditions and the decoupling between δ18O and δ13C, may be due to a high rate of oxygen exchange between sugars and xylem water (Pex) during cellulose synthesis, which dampens evaporative isotopic fractionation. |
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| Keywords: | Tree-ring width Carbohydrates |
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