Abstract:Soil available nitrogen in Dinghushan monsoon evergreen broadleaf forest assessed by using ion exchange resin bags showed significantly seasonal variations depending on diffferent forms of available nitrogen and on different depths of the soil.Ammonium(NH4+-N)was found to be the major form of the available nitrogen, and nitrate (NO3--N) in the soil at 10-20cm depth was significantly higher than that at 0-10cm depth (p=0.05), however,ammonium in the soil at 10-20cm depth tended to be lower than that at 0-10cm depth.