[A-HW22] Material transportation and cycling at the land-sea interface: from headwaters to the ocean

[AHW22-P15] Effects of unique snowmelt patterns and transboundary air pollution on water and material dynamics in forested watersheds in the Hokuriku region

*Yuko Itoh¹, Akira Ogura², Keiji Takase³, Yoichi Fujihara³, Yukari Takeuchi¹, Tayoko Kubota¹, Masahiro Kobayashi¹ (1.Forestry and Forest Products Research Institute, Japan, 2.Ishikawa Agriculture and Forestry Research Center Forestry Experiment Station, 3.Ishikawa Prefectural University)

In the forested watersheds of Ishikawa Prefecture in the Hokuriku region, atmospherically derived nitrogen inflows exceed 20 kg/ha/year. This value is comparable to the inflow of nitrogen-saturated watersheds in the Kanto region. In particular, during winter, the effects of transboundary air pollution from the Asian continent become more pronounced, and nitrogen inflows are more than twice as large as during summer. Because of its warm climate, the Hokuriku region has a different runoff pattern from that of colder regions, as snowmelt progresses simultaneously with snow accumulation. Therefore, the hydrologic processes that result from snowmelt patterns unique to warmer climates may specifically control the dynamics of nitrogen inflow in large amounts during the winter season and affect nitrogen saturation in forested watersheds.
Our purpose of this study was to clarify the effect of nitrogen from transboundary air pollution in a forested watershed in a warm snow-covered region.This study was conducted at the Ishikawa Forestry Experiment Station located in the middle reaches of the Tedori River in Ishikawa Prefecture. One observation system consisting of a large snow-melting lysimeter (3.6 m x 3.6 m) was installed in an open area and two in an adjacent cedar forest. We collected samples of snowmelt water flowing out from the snow bottom and observed water and material dynamics from inflow to outflow in the forest watersheds.