Tree-ring cores taken from four sites at different elevations in the middle of the Qilian Mountains, in the arid and semi-arid region of northwestern China, were used to develop four tree-ring width chronologies respectively using standard dendrochronological methods. Three of these namely Heiwa, Tianlaochi and Meiyaokou, are located in Sidalong, a catchments of the Heihe River, in the Qilian Mountains, northwestern China. These three sampling sites lie very close to each other but at the different elevatio...