Intensidade do azul em anéis de crescimento da conífera subtropical Araucaria angustifolia (Bertol.) Kuntze

Abstract

This study investigated the feasibility of Araucaria angustifolia as a dendroclimatic proxy in subtropical regions, focusing on tree-ring width (RW) and maximum latewood blue intensity (MXBI). The analyses revealed synchronicity between RW and MXBI chronologies, reflecting eco-physiological responses to climate variability. RW showed a positive correlation with precipitation from April to June of the previous year, suggesting that higher rainfall in the preceding autumn favors wider rings. In contrast, MXBI correlated with the mean temperature for the same period of the current year, indicating that higher temperatures enhance latewood lignification, resulting in greater optical intensity. These patterns highlight distinct climatic responses for each proxy, reflecting different growth cycle phases. MXBI was more strongly related to thermal variables, particularly mean autumn temperature, than to hydrological variables such as precipitation and the Palmer Drought Severity Index (PDSI), whose lack of correlation suggests that high water availability at the study site mitigates drought impacts on tree growth. The moderate correlation between MXBI and RW (r = 0.45, p = 0.002) indicates an interaction between anatomical and optical parameters in recording climate conditions. The EPS for MXBI was 0.745, lower than that of RW (0.894), demonstrating RW's greater robustness as a climate proxy. However, combining both proxies proved effective in reconstructing autumn temperatures. MXBI’s ability to reflect local thermal conditions during autumn is valuable for understanding climate changes in subtropical regions. Future studies should integrate multiple proxies and expand analyses to other ecological contexts to improve climate reconstructions and support conservation strategies.