Abstract: By using precipitation collection device and with ground surface nitrogen application, a randomized block design was adopted to study the effects of simulated increased precipitation and nitrogen deposition on the vegetation productivity of typical Caragana microphylla community in Horqin Sand Land. When the precipitation increased by 1/7, the mean vegetation height had no significant increase, but the vegetation biomass increased by 17.6%. When the precipitation increased by 2/7, the mean vegetation height increased by 23%, and the vegetation biomass increased by 31.8%. One-year nitrogen deposition had no significant effects on vegetation biomass. Therefore, precipitation could be the key factor affecting the vegetation productivity on sandy land. The vegetation productivity had a rapid response to increased precipitation, while short-term increased nitrogen deposition had little effects on the vegetation productivity.

Key words: Mangroves, Soil, Particle size distribution, Fractal dimension