[M-IS14] 生物地球化学

[MIS14-P02] 都市近郊林における大気由来のリン沈着量の計測

張 璐¹、*智和 正明¹、鄭 聖勳¹、井手 淳一郎²、大槻 恭一¹ (1.九州大学農学部附属演習林、2.九州大学 持続可能な社会のための決断科学センター)

キーワード：大気窒素沈着、乾性沈着、リン酸塩、溶存有機リン、林内雨

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 (PO₄^3-) 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.