Runoff reconstruction for the Bailong River from tree rings back to AD 1601, reveals changing hydrological signals of China north-south transition zone

We present a runoff reconstruction for the Bailong River based on the composite chronology developed from four sampling sites of Pinus tabulaeformis in the China north-south transition zone. The runoff reconstruction, spanning 1601-2013 CE, was developed by calibrating tree-ring data with the instrumental runoff record. Runoff reconstruction accounted for 44.3% of the actual runoff variance during the common period 1958-2010 and provided a long-term perspective on hydrological change in the China north-south transition zone. In the past 413 years, high- and low-runoff years accounted for 15.50% and 15.98%, respectively. Of all the 17 extreme hydrological events, 14 of them are extremely high-flow years, and 17th century was the wettest period during the past 413 years. The preliminary analysis results show that there is a relationship between our runoff reconstruction and the Atlantic Multidecadal Oscillation (AMO) at multidecadal scale. Since the 1990s, runoff in the China north-south transition zone has also seen a significant decrease as a result of dry trends of the source region.本研究基于中国南北过渡带内4个油松（Pinus tabulaeformis）采样点建立的复合年表，构建了白龙江流域的径流重建序列。该序列的时间跨度为公元1601年至2013年，通过将树轮数据与器测径流记录进行校准得以完成。在1958年至2010年的公共校准时段内，该径流重建序列可解释实际径流方差的44.3%，为探究中国南北过渡带的水文变化提供了长期视角。在过去413年间，丰水年与枯水年分别占总年份的15.50%与15.98%。在全部17次极端水文事件中，14次为极端丰水年份，且17世纪为过去413年间最为湿润的时期。初步分析结果显示，本研究的径流重建序列与大西洋多年代际振荡（Atlantic Multidecadal Oscillation, AMO）在多年代际尺度上存在相关关系。自20世纪90年代以来，受流域源区干旱化趋势影响，中国南北过渡带内的径流量已出现显著下降。