Net CO2 exchange and carbon isotope flux in Acacia mangium plantation Surface Flow in an Acacia mangium Plantation and an Orchard in Heshan, Guangdong Province, China Carbon Density and Storage of Acacia mangium Plantation Ecosystem in Nanning, Guangxi Studies on Soil Fertility Change in Acacia mangium Plantation in Nanning,Guangxi Microelements Distribution and Biological Cycling of Acacia mangium plantation in Nanning,Guangxi Biological cycling of nutrients in different ages classes of Acacia mangium plantation