Abstract: To verify the effect of afforestation on soil fertility on abandoned limestone hill,a vegetation restoration experiment with different planting types of trees had been conducted in 1974.Soil samples under different types of trees were collected in March 2006.Soil nutrients improved significantly(P<0.05) after 32-year vegetation restoration.The amount of soil total nitrogen and phosphorous,available nitrogen and potassium at Choerospondias axillaris site increased at maximum extent by 84.62%,55.56%,79.20% and 109.76% respectively compared with control.The great increase in soil available phosphorous and organic matter was observed at Firmiana simplex site,respectively by 292.73% and 75.40%.The similar increasing tendency was also observed for soil organic pool,soil total organic carbon(TOC),soil water-soluble organic carbon(WSOC) and microbial biomass carbon(MBC) were much more abundant(P<0.05) at Ch.axillaries,F.simplex and Sapindus mukorossi sites than those at control site.Soil WSOC and MBC at Cupressus funebris and Robinia pseudoacacia sites were more abundant(P<0.05) compared with those at control site although soil TOC was found no different between them.Soil pH was lowered(from 8.01 to average 7.3) as a result of afforestion.In comparison of different treatments,it can be concluded that Ch.axillaris had the most power on improvement in soil quality,and followed by F.simplex and S.mukorossi,C.funebris and R.pseudoacaia had the least.

Key words: limestone, abandoned hill, afforestation, soil nutrient, soil labile organic carbon