A "janela de alívio" hidrológica: sazonalidade do crescimento radial em Salix humboldtiana Willd. sob estresse por hipóxia em planície de inundação neotropical

Abstract

Dendrochronology aims to date the exact year of growth ring formation in order to understand climate–growth relationships over time. In the tropics, this field has faced the paradigm that the presumed lack of seasonality would prevent the formation of annual rings, leading to a delay in comparison to temperate regions. As a result, many tropical tree species have not yet been explored regarding their dendrochronological potential. In this context, the present study evaluated the dendrochronological potential of Salix humboldtiana Willd. in a riparian region of the Rio Grande Basin, Minas Gerais, Brazil. A total of 48 trees (DBH ≥ 10 cm) were sampled using a non-destructive method with a Pressler increment borer, of which 11 individuals were selected for the final chronology due to the observed synchrony. The quality of crossdating and the removal of biological trends were assessed using COFECHA and ARSTAN software, with climatic data obtained from the Climate Research Unit (CRU) database. A 19-year chronology (2005–2024) was developed, showing an Expressed Population Signal (EPS) of 0.93. The results suggest that radial growth is influenced by hydrological dynamics: during the rainy season, river overflow appears to induce stress due to hypoxia or anoxia, suggesting a functional dormancy that interrupts cambial activity. In contrast, the decline in river levels during the dry season (May to August) seems to establish a “relief window,” allowing the resumption of radial increment. Although a trend of response to precipitation (R = 0.41; p = 0.077) and to evaporative demand (r = −0.32 in August) was observed during this period, the climatic signals still show a diffuse pattern. Therefore, although S. humboldtiana demonstrates potential for dendrochronological studies, establishing this species as a reliable environmental sensor for the region requires expanding the sampling network and conducting investigations that isolate the effect of artificial flow regulation on wood formation.