Divergent climate-growth responses in radial growth of Chinese pine forests with varying health conditions in the semi-arid Loess Plateau, China.

Introduction: Global climate change-induced extreme drought has triggered widespread forest growth decline and tree mortality worldwide, making the processes of forest decline and their responses to environmental conditions a major research focus. In the Longtan Catchment of the Loess Plateau, Chinese pine ( Methods: We developed tree-ring width chronologies for Chinese pine plantations representing five distinct health conditions: healthy, relatively healthy, slightly declining, moderately declining, and severely declining. Standard dendrochronological techniques were employed to compare growth rates, chronology statistical quality, and the sensitivity of radial growth to climate variables during both the growing and non-growing seasons. Results: The results showed that the healthy chronology exhibited a clear increasing trend in growth rate over time and relatively high statistical quality. In contrast, declining chronologies showed no evident long-term increase in growth rate and were characterized by lower chronology quality. Regarding climate responses, the strength of climate signals during the growing season decreased progressively with increasing decline severity. While healthy trees displayed strong positive correlations with climate variables, these relationships weakened and shifted toward negative associations in the moderately and severely declining stages. Similarly, positive climate signals in the non-growing season declined markedly along the health gradient, weakening substantially in the severely declining stage. Discussion: These findings deepen our understanding of growth decline and its environmental drivers in the Loess Plateau. The health-dependent sensitivity shifts identify a critical window for proactive intervention. Our study suggests that early detection and timely density regulation, such as thinning during mild-to-moderate decline, are essential. Furthermore, management strategies should prioritize conserving non-growing-season water-especially spring moisture-to mitigate the risk of severe forest decline and support sustainable ecological restoration.