CO2 and water vapor exchange of a larch forest in northern Japan

In the northern part of East Asia, forests dominated by larch are extensively distributed and probably play an important role in the global carbon cycle. However, a knowledge of the CO2 balance of larch forests based on long‐term flux measurements is very restricted in East Asia. Thus, a long‐term flux measurement has been started in 2000 at a larch plantation on a flat terrain in Hokkaido, Japan to obtain more information on the CO2 and energy balances of larch forests. From September 2000 to August 2001 the net ecosystem CO2 exchange (NEE) changed seasonally in accordance with the annual cycles of phenology and climate. NEE was negative for six months of the growing season, May–September; the larch ecosystem was a carbon sink with a peak intensity of –0.38 mol m−2 d−1 for this period. In the leafless season from November to April the forest ecosystem was a carbon source with an intensity ranging between 0 and 0.05 mol m−2 d−1. Annual NEE from September 2000 to August 2001 was −24.4 to −32.4 mol m−2 yr−1 (=−293 to −389 gC m−2 yr−1); this value is compatible with those reported from other temperate forests. Annual evapotranspiration for the same period was 367 mm, which was only 29% of annual precipitation.