Site description
This study was conducted at the Guanzhuang National Forestry Farm, Sanming City, Fujian Province, South China (117°43′E, 26°30′N). This region has a subtropical monsoon climate with a mean annual temperature ranging from 18.8 to 19.6 °C and a mean annual precipitation ranging from 1,606 to 1,650 mm (Wu et al. 2013). The Farm contains a 5173-ha Chinese fir (Cunninghamia lanceolata ) planation, which was planted in 1992 (Fan et al. 2014). The test soil is classified as a mountain red soil. Annual average wet N deposition (including soil nitrate and ammonium nitrogen) resulting from rainfall in the Sanming region was reported to range from 4.2 to 5.7 g N m-2year-1 (Fan et al. 2014).