Tree-ring wood density reveals differentiated hydroclimatic interactions in species along a bioclimatic gradient

Climate variations are influencing the growth dynamics of forests, with direct consequences on their biomass productivity. The scientific community, concerned with refining the understanding of tree-climate interactions, has recently used tree-ring density to elucidate ecological mechanisms that may be overlooked by earlywood, latewood, and total tree-ring widths. In this study, we model the sensitivity of intra-annual wood density in tree-rings for 15 species distributed across a broad bioclimatic and biodiverse gradient in the Mexican Republic. Maximum, minimum, latewood, and earlywood density (MaxD, MinD, LWD, and EWD, respectively) were associated with climatic data through correlation analysis and mixed-effects models. Maximum temperature (T_MAX) and precipitation (P) stand out as key drivers of temporal density fluctuations, notably influencing MaxD and LWD as indicators of hydroclimatic regime changes. MinD and EWD are less responsive but prove valuable in gauging environmental sensitivity. Abies religiosa from the Southern Semi-Arid Highlands and Picea martinezii from Mediterranean California were the most responsive species to climate variables. These results open new paradigms for densitometry as a proxy for ecological processes that species face in anticipating dieback phenomena, mortality rates, and resilience mechanisms, with implications for productivity and carbon rates in the face of predicted climate variations. However, the wood density-climate relationship is even more complex, and integrative research combining other proxies (e.g., wood anatomy and chemical composition) is recommended to refine wood density variations and understand the causes of the interspecific differences found in this study.