Changes in pH, CEC and exchangeable acidity of some forest soils in southern China during the last 32-35 years

Soil acidification has been occurred in two locations in southern China. Th e changes in soil pH during a 35 yl period has been about 1.0 pH (H2O) unit s, and about 0.58-0.71 pH (KCI) units at Wuming in Guangxi Zhuang Autonomou s Region and Zhurongfeng of Mt. Heng in Hunan Province. A decrease in CEC a nd BS and an increase in hydrogen and aluminum ion concentrations were foun d in the acidified soils, and related to the acidification caused by acid d eposition. Hydrogen ion concentration increased about 0.1-1.0 x 10(-6) equi valent g(-1) soil yr(-1). Cation exchangeable capacity (CEC) and base satur ation (BS) decreased to 53-76 and 30-59% in the acidified soils respectivel y, and an increase in exchangeable acidity also occurred. Acidification in the topsoil is higher than in the subsoil.