Abstract: The patterns of heavy metals in deciduous forest floor along an urban suburban rural gradient(transect 140km×20km)in New York were analyzed. 25 sampling quadrats(20m×20m)of Quercus forests in 9 study areas along the gradient were located and 4 samples of 15cm×15cm of litter patches in each quadrat were collected and analyzed for concentrations of Cu, Pb, Ni, Cr, Mn, Co, Zn and Cd in laboratory. The result reveals the relationships between urbanization and economic activities and the heavy metal pollution of forest floor. DCA analysis show that urban is greater than suburban, suburban greater than rural in total heavy metals. The concentration of heavy metals especially for Pb, Cu, Ni and Cr are decreased significantly along the gradient from city core to rural area. This is closely related to human activities. The concentrations of heavy metals are significantly negative correlated with the distance from the city core, urban land use, population in density, traffic density and road density. Heavy metals in forest floor are mainly from air pollution due to tail gases of automobiles because this area is not industrial area, no other important pollutant resources. Althouth unleaded gasoline has been used for decades in United States, Pb pollution is severe in this area. Ecological gradient of forest along urban-suburban-rural is an effective way to study the relationships between environmental pollution and urbanization.

Key words: Pollution of heavy metal, Forest floor, Human economic activities, Natural protection, Ecological transect.