High potential for increase in CO2 flux from forest soil surface due to global warming in cooler areas of Japan

The CO(2) fluxes from the forest floor were measured using a closed chamber method at 26 sites from 26 degrees N Lat. to 44 degrees N Lat. in Japan. Seasonal fluctuation in CO(2) flux was found to correlate exponentially with seasonal fluctuation in soil temperature at each site. Estimate of annual carbon emission from the forest floor ranged from 3.1 to 10.6 Mg C ha(-1). The emission rate of soil-organic-carbon-derived CO(2), obtained by incubation of intact soil samples, correlated closely with the carboxymethylcellulase (CMCase) activity in the soil. The sum of cool-water soluble polysaccharides, hot-water soluble polysaccharides, hemicellulose, and cellulose content in the soil was greater at the sites with low CMCase activity than that at the sites with high CMCase activity. Because the sites in cooler-climate sites had a high content of easily decomposable soil organic carbon and organic litter, the potential increase in CO(2) efflux from forest floor with increasing soil temperature would be greater in cooler-climate sites.