Abstract:Hainan Island is the biggest tropical region in the South of China.In the island,soil erosion and degradation are important ecological problems related to the increase of population and land use in the last 30 years.In order to evaluate the fertility of soil and set up the model for recovering the forest vegetation,a study was carried out on old-fields abandoned 2 to 20 years ago,near the Haikou city(20°02′N,110°15′E,altitude 30~40 m a.s.l) The area belongs to the wet tropical monsoon region.Mean annual rai...