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

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 (δ18OTR) 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 δ18OTR values. During dry years, a wider range of responses was observed in growth, density and STR, while lower CaTR and enriched δ18OTR values were found. The annual centennial chronologies spanning from 1835 to 2018 showed good calibration skills for reconstructing local precipitation, evapotranspiration (P-PET), Amazon-wide rainfall, as well as climate modes related to sea surface temperature (SST) anomalies such as El Niño 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 δ18OTR explained 60 % and 57 % of the variance of Amazon rainfall (1960-2018) and El Niño 3.4 (1920-2018), respectively. Our results show that a multi-proxy tropical tree-ring approach can be used for high-reliable reconstructions of climate variability over Amazon basin at inter-annual and multidecadal time scales.

Studies on cambial activity: advances and challenges in the knowledge of growth dynamics of Brazilian woody species.

The lack of specific research on the sequence of events that determine plant growth from meristem until wood formation represents a gap in the knowledge of growth dynamics in woody species. In this work, we surveyed published studies concerning cambial activity of Brazilian native species aiming at allowing the comparison of applied methods and obtained results. The annual cambial seasonality was observed in all the investigated species. Nevertheless, we found high heterogeneity in the used methodologies. As a result from this analysis, our opinion points to the need for standardizing sampling protocols and for discussing the suitability of experimental designs. This will help to define with greater precision the factors that determine the radial growth in the different tropical ecosystems.