Climate variability of the southern Amazon inferred by a multi-proxy tree-ring approach using Cedrelafissilis Vell

Abstract

The analysis of climate variability and development of reconstructions based on tree-ring records in tropical forests have been increasing in recent decades. In the Amazon region, ring width and stable isotope long-term chronologies have been used for climatic studies, however little is known about the potential of wood traits such as density and chemical concentrations. In this study, we used well-dated rings of Cedrela fissilis Vell. from the drought-prone southern Amazon basin to assess the potential of using inter-annual variations of annually-resolved ring width, wood density, stable oxygen isotope (818OTR) measured in tree-ring cellulose and concentration of Sulfur (STR) and Calcium (CaTR) in xylem cells to study climate variability. During wet years, Cedrela fissilis produced wider and denser rings with higher CaTR and lower STR, as well as depleted 818OTR values. During dry years, a wider range of responses was ob-served in growth, density and STR, while lower CaTR and enriched 818OTR values were found. The annual centennial chronologies spanning from 1835 to 2018 showed good calibration skills for reconstructing local precipitation, evapo-transpiration (P-PET), Amazon-wide rainfall, as well as climate modes related to sea surface temperature (SST) anom-alies such as El Nino South Oscillation (ENSO), Tropical Northern Atlantic (TNA), and the Western Hemisphere Warm Pool (WHWP) oscillations. CaTR explained 42 % of the variance of local precipitation (1975-2018), RW explained 30 % of the P-PET variance (1975-2018), while 818OTR explained 60 % and 57 % of the variance of Amazon rainfall (1960-2018) and El Nino 3.4 (1920-2018), respectively. Our results show that a multi-proxy tropical tree-ring ap-proach can be used for high-reliable reconstructions of climate variability over Amazon basin at inter-annual and multidecadal time scales.

The analysis of climate variability and development of reconstructions based on tree-ring records in tropical forests have been increasing in recent decades. In the Amazon region, ring width and stable isotope long-term chronologies have been used for climatic studies, however little is known about the potential of wood traits such as density and chemical concentrations. In this study, we used well-dated rings of Cedrela fissilis Vell. from the drought-prone southern Amazon basin to assess the potential of using inter-annual variations of annually-resolved ring width, wood density, stable oxygen isotope (818OTR) measured in tree-ring cellulose and concentration of Sulfur (STR) and Calcium (CaTR) in xylem cells to study climate variability. During wet years, Cedrela fissilis produced wider and denser rings with higher CaTR and lower STR, as well as depleted 818OTR values. During dry years, a wider range of responses was ob-served in growth, density and STR, while lower CaTR and enriched 818OTR values were found. The annual centennial chronologies spanning from 1835 to 2018 showed good calibration skills for reconstructing local precipitation, evapo-transpiration (P-PET), Amazon-wide rainfall, as well as climate modes related to sea surface temperature (SST) anom-alies such as El Nino South Oscillation (ENSO), Tropical Northern Atlantic (TNA), and the Western Hemisphere Warm Pool (WHWP) oscillations. CaTR explained 42 % of the variance of local precipitation (1975-2018), RW explained 30 % of the P-PET variance (1975-2018), while 818OTR explained 60 % and 57 % of the variance of Amazon rainfall (1960-2018) and El Nino 3.4 (1920-2018), respectively. Our results show that a multi-proxy tropical tree-ring ap-proach can be used for high-reliable reconstructions of climate variability over Amazon basin at inter-annual and multidecadal time scales.