Earlywood and latewood density in pines from northern subtropical China exhibit distinct and robust climate signals

Abstract

Tree-ring densitometric parameters are essential tools in ecological and climate change studies. Among these, maximum latewood density (MXD) is the most widely used for summer temperature reconstructions, particularly in high-latitude and high-elevation regions where tree growth is primarily limited by temperature. In drought-prone sites, minimum earlywood density (MND) has been shown to reflect moisture variability. However, the application of these parameters in tropical or subtropical regions has been less well-explored. In this study, we conducted tree-ring densitometric studies in a northern subtropical forest of China to investigate the potential of tree-ring density parameters for climate reconstructions. MND exhibited significant positive correlations with maximum temperature and negative correlations with the Standardized Precipitation Evapotranspiration Index (SPEI) during May-June. MXD showed analogous response patterns to the same climate factors during August–September. Based on these robust correlations, we reconstructed the maximum temperatures during May-June and August-September separately. However, no synchronization was observed between these two temperature reconstructions on annual scale. Our study represents one of the first comprehensive densitometric investigations capturing extensive and strong climatic signals, highlighting the great potential of tree-ring densitometric parameters for climate reconstruction within subtropical regions.