Drought is one of the most devastating natural disasters affecting the people living in ecologically vulnerable regions. Therefore, scientists try to find a effective method to prodict and analyse variations of drought on a larger time scale. 

As a widely used paleoclimate proxy, tree rings from drought sensitive sites provide annually resolved climate records covering centuries or even millennial. 

However, we still know little about hydroclimatic conditions in the arid northwest China during the medieval period, due to lack of accurately dated proxy records, and ambiguous hydroclimate signals. 

Recently, a research group led by Prof. YANG Bao from Northwest Institute of Eco-Environment and Resources (NIEER) of the Chinese Academy of Sciences reported a 1556 year-long tree-ring width chronology for the Hexi Corridor to calculate a chronology based on 416 Qilian juniper ring-width samples. 

Scientists used a ring-width chronology to reconstruct the May-June mean scPDSI (self-calibrating Palmer Drought Severity Index) over the past 1556 years. The study results showed that drought in early summer (May-June) is the primary controlling factor for tree growth in the Hexi Corridor. 

The study explains more than 40% of the observed moisture variance over the period 1951-2011 CE, and shows two multi-centennial droughts during 800-950 CE and 1000-1200 CE, and two multi-centennial pluvial periods during 1200-1450 CE and 1510-1620 CE. 

The Hexi Corridor and Qaidam Basin experienced common multi-decadal wet conditions in 1210-1250 CE, 1310-1420 CE and 1530-1620 CE, and common dry conditions in 1100-1160 CE, 1430-1520 CE and 1660-1730 CE. Moreover, the comparative study also revealed regional differentces in tree growth at multi-centennial timescales between the two regions. 

This study is the first millennium-long, annually-resolved hydroclimate reconstruction for the Hexi Corridor. 

The study entitled “A 1556 year-long early summer moisture reconstruction for the Hexi Corridor, Northwestern China” was published in Science China Earth Sciences.