Ecosystem respiration derived from 222Rn measurements on Rishiri Island, Japan

We evaluated the nighttime CO2 flux (ecosystem respiration) on Rishiri Island, located at the northern tip of Hokkaido, Japan, from 2009 to 2011, by using the relationship between atmospheric 222Rn and CO2 concentrations. The annual mean CO2 flux was 1.8 μmol m−2 s−1, with a maximum monthly mean in July (4.6 ± 2.6 μmol m−2 s−1) and a broad minimum from December to March (0.33 ± 0.29 μmol m−2 s−1). The annual mean was comparable to fluxes at the JapanFlux sites in northern Japan. During the season of snow cover (mid-December to early April), the CO2 flux was low (0.45 ± 0.43 μmol m−2 s−1). Total annual respiration was estimated at 679 ± 174 g cm−2, about 8 % of which occurred during the season of snow cover.