1 Net Soil Nitrogen Mineralization and Nitrification of Lowland Subtropical Rain Forest in Southern Taiwan

The Nanjenshan Ecological Reserve Site is a major contributor for biodiversity because of its biographic value and abundance of endemic plant species with restricted distributions in the south of Taiwan. Our research was conducted in a one-ha transect along the ridge of Nanjenshan (120°51’10’’E, 22°03’37’’N). Previous studies indicated that there are significant differences of floristic compositions and soil properties along the altitudinal gradient, ranging from 300 m to 480 m. The objective of this study is to investigate the relations between soil nitrogen transformation and landscape positions in the study area by laboratory incubation. Mineral surface soils (0-15 cm) were collected from three replicate 10 m ×10 m plots of footslope and summit landscape position, respectively. Soils were sampled in Feb 2004 and Feb 2005 and incubated in the laboratory under field moisture condition at intervals of 1 to 15 weeks, then extracted by 2M-KCl at the end of incubation. Soils sampled in Oct and Dec 2004 were incubated for short-term (28 days) and extracted by 2M-KCl weekly. Inorganic N (ammonium N and nitrate N) of extracts were analyzed by the Kjeldahl apparatus. Soil microbial biomass C and biomass N of each soil sample were also measured