[Seminar] Prof. Masahito Ueyama

Biosphere-atmosphere interaction in boreal ecosystems under changing climate

Boreal forests, so called taiga, occupy the circum-polar land between the north dominated by arctic tundra and south dominated by temperate forests. They occupy approximately 9% of the total land, and accumulate up to 23% of global soil carbon stock. The northern high latitude regions have experienced 3.1 o C warming during the past 40 year; warming speed is three times of the global mean of the warming. In the lecture, I review environmental changes currently happened in the northern high latitudes: sea ice declining, greening vegetation, prolonged growing season of vegetation, permafrost degradation, and increasing and intensified wild fires. Then, I introduce our research activities, monitoring biosphere-atmosphere interaction in boreal forests in Alaska. First, I introduce the eddy covariance method, which is the key technique for monitoring fluxes between ecosystem and the atmosphere. Then, I introduce long-term measurements of CO 2 flux at a lowland black spruce forest on the ice-rich permafrost in Fairbanks, Alaska (US-Uaf site registered in AmeriFlux; Ueyama et al., 2014) and measurements of CO 2 flux at two burned forests after fire (US-Rpf and US-Fcr sites; Ueyama et al., 2019). Finally, I introduce regional CO 2 flux based on the upscaling CO 2 fluxes measured at multiple sites, through international collaborations (Ueyama et al., 2013; Virkkala et al., 2021).