In order to understand the influence of urbanization on distribution of heavy metals in soils,concentrations characteristics of 7 heavy metals(Zn,Cu,Ni,Pb,As,Cd,and Hg) in various forest types were investigated along an urban gradient in Changsha,a capital city of Hunan Province,China.The concentrations and potential ecological risk of heavy metals in the urban soils was assessed when compared to the background values of heavy metals in soils in both Changsha city and Hunan Province.A total nineteen major forest types were selected at three locations(namely urban district location,urban fringe location,and suburban location) along the urban gradient degree in urban forests soil in the Changsha city.Two forest plots(each with the size of 20m × 20m) were built in each forest types.Three subplots were(each with an area of 1 m2) were set up in each of the plots.Five soil samples(from 0—20 cm depth) were randomly taken within each subplot and pooled to a soil sample for heavy metals chemical analysis,0—20cm soil samples were collected from different urban gradient(urban district,urban fringe,suburban) forest to analyze the concentrations of Zn,Cu,Ni,Pb,As,Cd,and Hg,and the potential ecological hazard assessment indices by Hakanson was used to assess the soil heavy metals potential ecological risk degree in urban forest,based on the background values of soil in Changsha City and in Hunan Province.Results showed that the average concentration of the same heavy metal elements in urban forest soils tended to increase with degree of urbanization.Pb had the maximum increasing value and As the minimum.In the same urbanization location degree,Zn had the highest average concentration and Cd had the lowest one among the studied of all test heavy metals.,On average,while the average the concentrations of all examined heavy metals them in study sites were lower than those in the Environmental Quality Standard for Soil(Ⅱgrade) in China.,.The heavy metals whose concentrations were higher than the background values in Changsha cite and the accumulation tendency of test heavy metals in urban forest were as in the order as of CdHgAsPbCu(Ni)Zn in the study sites.The concentration of re existed some differences in the same heavy metal element varied concentration with among different types forest types in the city,The average concentrations of Zn,Cu,Pb,As,and Hg were as higher in Osmanthus fragrans forests and,Cinnamomum camphora Presl.and Osmanthus fragrans mixed forests,but that of Cu,Ni,As,Cd,and Hg were found to be was low concentrations in Cinnamomum camphora Presl.+ Pinus massoniana mixed forests and,Osmanthus fragrans +Elaeocarpus sylvestris Poir mixed forests,the spatial distribution patterns of Pb and Zn was significant different in the study area,while Cd,Ni and As were more evenly distributed.Significant correlations were found among Zn,Cu,Ni,Pb,As,Cd,and Hg concentrations in soils(P 0.05),except the relationships between Cd and As,and Ni.The 7 heavy metals had positively significant correlations with soil organ matter.It was found that Zn,Cu,Ni,Pb,As,Cd and Hg mainly came form the anthropogenic inputs in the urban district forests.Based on potential ecological risk assessment,the situation of heavy metals was in the medium ecological risk level in urban district locations,was in closing to the medium level in urban fringe locations,and was in a slight level in suburban locations in Changsha cite.Among the studied heavy metals,Zn,Cu,Ni,Pb,and As were in a slight risk level,while Cd and Hg were in medium or strong ecological risk level.Our study provided scientific reference to estimate and evaluate the impact of urbanization on heavy metals in Southern China.