An 850-year tree-ring-based reconstruction of drought history in the western Qilian Mountains of northwestern China

Studies of regional drought history will be helpful for understanding current hydroclimate variability with global warming as well as predicting future hydroclimate shifts. Long-term tree-ring records are scarce in the western Qilian Mountains of northwestern China, which is also the western boundary of the natural distribution of Qilian Juniper (Juniperus przewalskii Kom.) in this area. Here, we present an 850-year (AD 1161-2010) reconstruction of May-July self-calibrating Palmer Drought Severity Index (scPDSI) in the western Qilian Mountains that is based on two nearly millennia of ring-width chronologies derived from long-lived Qilian Juniper trees. The reconstruction suggests a relatively dry phase from the 15th century to the 18th century during the Little Ice Age (LIA) and a relatively wet period over the past two centuries. This reconstruction is consistent with other tree-ring-based hydroclimatic reconstructions from the northeastern Tibetan Plateau, as well as the corresponding century-scale solar activity during the LIA. The three mega-drought periods (AD 1260s-1340s, 1430s-1540s and 1640s-1740s) recorded by the tree-ring series also correspond to the Wolf, Sporer and Maunder solar activity minimum periods. Results of the multi-tape method analysis and wavelet analysis further confirmed the relationship between regional hydroclimate variability and solar activity forcing.