Increased N deposition has altered the internal N cycling of forest ecosystems in many places world-wide. Disturbances of external nitrogen on soil nitrogen dynamics are the key processes determines the responding feature of the ecosystem. So far, most of the indicators used to quantify the effects of excessive nitrogen inputs are for temperate and boreal forests. Relatively little works have been done for subtropical forests. Effective indicators, which can quantitively assess the effects of external nitrogen on soil nitrogen dynamics in subtropical forest ecosystems are urgently needed. Here in this work, soil nitrogen dynamics of two 40 to 45 year old masson pine(Pinus massoniana Lamb) forests at Tieshanping (TSP, near Chongqing City) and Caijiatang (in Shaoshan, Hunan province), receiving high atmospheric N deposition (25 to 49 kg ha-1 yr-1), have been investigated by in situ and lab incubation methods. In the meanwhile, several indicators for N dynamics and leaching, suggested for temperate and boreal forest ecosystems were verified to quantify the effects of increased N deposition inputs on soil N dynamics and N cycling of Chinese subtropical forests.

Key words: Quantify, effects of N deposition, indicators, siol nitrogen dynamics, subtropical forest ecosystem, China