Climate-growth pattern of Pinus tabulaeformis plantations and their resilience to drought events in the Loess Plateau

Large-scale plantations were established under the Grain for Green project to improve the ecological environment of the Loess Plateau (LP) of China. However, there are increasing concerns regarding the sustainability of plantation ecosystems under climate change. In this study, we developed tree-ring width chronologies of Pinus tabulaeformis at seven sites along a precipitation gradient from south to north in the LP. Correlation analysis was performed to investigate the climate (temperature, precipitation, self-calibrating Palmer Drought Severity Index)-growth relationship. Moreover, the tree resilience components were computed to study the adaptability of trees to extreme drought during the growth periods. The results showed that the differences in radial growth to climate change along the precipitation gradient and the cluster analysis of the tree ring width index (RWI)-scPDSI correlation coefficient illustrated that the climate-growth response pattern along the LP was divided into southern and northern regions. Tree growth in the southern region is limited by humid environment conditions, while tree growth in the early and middle growing seasons of the northern region is limited by warming-induced drought. As the temperature rising over the past fifty years, the growth was found to be negatively correlated with temperature, especially in the spring and autumn seasons of the northern region. In contrast, the effect of precipitation on tree growth became more negative in the southern region, but more positive in the middle and late growing seasons of the northern region. Moreover, tree resilience analysis showed that the high resistance of Pinus tabulaeformis in the southern region, whereas high recovery in the northern region. It was difficult for the growth of Pinus tabulaeformis to recover from drought in the southern region, but stronger adaptability to extreme drought events in the northern region. Our study illustrated that there are different climate response patterns and limiting factors of Pinus tabulaeformis along the precipitation gradient in the LP; thus, different ecological restoration and regional forestry management strategies should be initiated in the LP.