investigation on function of wetlands under influence of land uses (a case study: higashi-hiroshima, japan)

impacts of land use types on wetland functions were investigated in three surface water wetlands, located in west japan. nitrogen concentration was monthly sampled and measured in input, output and inside of the wetlands. findings of the present study revealed that function of the wetlands and its capabilities for reduction or remove of the nutrients from surface water are varied by change in the land use type in catchment of the wetlands. the wetland of high percentage of urban land use in its catchment had a minimum function in reduction of nitrogen concentration. it also revealed no seasonal function in reduction of nitrogen concentration. a steady-state function in reduction of nitrogen concentration was observed in the wetland of moderate percentage of urban cover, while seasonal fluctuations were observed in reduction of nitrogen concentration. although the wetlands had an efficient role in reduction of nutrients in their out-flowing water, these capabilities would be degraded in case of over-changing the land use types in their catchments and in turn cause the wetlands act as a source of nutrients in downstream water resources.