Beijing Normal Univ, Key Lab Environm Change & Nat Disaster, Minist Educ PR China, Inst Desert Resources Res, Beijing 100875, Peoples R China;
Hebei Univ Engn, Resource Coll, Handan 056038, Peoples R China;
Hedong; sandy; land; of; Ningxia; tree-ring; width; annual; precipitation; correlation;