Tree-ring recorded moisture variations over the past millennium in the Hexi Corridor, northwest China

摘要

Knowledge of the moisture variation is essential for water resources management and policy making, especially for the arid regions, where the water resources can hardly meet the demand of the human being and the ecosystem. Hexi Corridor in northwest China is in a typical arid area with little precipitation and high evaporation. A lot of tree-ring studies were conducted in this area; however, no long-term and large-scale moisture history research had been conducted in this region until now, due to the lack of long-time tree-ring records in eastern and western Qilian Mountains. Here, we synthesized the moisture evolution of nearly one millennium (AD 1161-2006) in this region by using four published moisture- sensitive tree-ring records, including two recently published millennium reconstructions in eastern and western Hexi Corridor. The comparisons of tree-ring records from the eastern, central and western part of Qilian Mountains show that all the reconstructions are statistically similar to each other. The principal component analysis was applied to extract the common signal recorded by these series. The first principal component (PC1), which expressed 61.1% of the total variance, was used as an indicator of regional moisture variations. The PC1 suggests that the Hexi Corridor has alternated between contrasting climatic conditions, with dry periods at AD1161-1216, 1260-1349, 1409-1417, 1443-1510, 1617-1737, 1759-1838 and 1929-1948, wet periods at AD1217-1259, 1350-1408, 1418-1442, 1511-1616, 1738-1758, 1839-1928 and 1949-2006. The droughts and pluvial periods identified in the Hexi Corridor are generally consistent with those in nearby regions recorded by tree-ring and other proxies. We also find that droughts periods in the Hexi Corridor trend to coincide with the solar minimum, highlighting the importance of solar variability on forcing regional moisture variability.