Keywords:Atmospheric nitrogen deposition, Dry deposiiton, Phosphate, Dissolved organic phosphorus, Throughfall
Atmospheric P deposition contributes significantly to P source as well as rock weathering. However, quantitative information is limited about atmospheric P deposition, especially dry deposition, when evaluating the effects of elevated N deposition on N saturation in temperate forested ecosystems where other nutrients including P could be limited. This study measured atmospheric P deposition using throughfall method as well as bulk rainfall to evaluate the contribution of atmospheric P deposition to P cycling in advanced stage of N-saturated forested ecosystems, suburban area, Fukuoka, western Japan. Throughfall and stemflow were collected in the forested site and rainfall was also collected at nearby open sites from October 2016 to September 2017. Dissolved total phosphorus (DTP), consisting of phosphate (PO43-) and dissolved organic phosphorus (DOP), were measured. Atmospheric N deposition was 9.3 kg N ha-1 yr-1 via bulk deposition and 17.6 kg N ha-1 yr-1 via throughfall plus stemflow, indicating high atmospheric N deposition enough to potentially induce N saturation in forested ecosystems. Atmospheric wet and dry deposition of DTP was 0.036 and 0.009 kg P ha-1 y1-1, respectively. Kosa phenomenon increased dry deposition of particulates including Ca2+ and DTP. However, total atmospheric P deposition in this study sites was considerably lower than the referred values in other sites, suggesting that the lower atmospheric P deposition at the study site may contribute to advanced N saturation in forested ecosystems. Overall, we highlight the need for information about atmospheric P deposition when assessing the impacts of N deposition.