Vertical soil-air CO2 dynamics at the Takayama deciduous broadleaved forest AsiaFlux site

• Published in: Journal of forest research 2013-02, Vol.18 (1), p.49-59
• Main Authors: Yonemura, Seiichiro, Yokozawa, Masayuki, Sakurai, Gen, Kishimoto-Mo, Ayaka W., Lee, Nayeon, Murayama, Shohei, Ishijima, Kentaro, Shirato, Yasuhito, Koizumi, Hiroshi
• Format: Article
• Language: English
• Subjects: Biomedical and Life Sciences; Carbon; Carbon cycle; Carbon dioxide emissions; Deciduous forests; Diurnal variation; Ecosystems; efflux; Forest soils; Forestry; Forestry Management; Life Sciences; National parks; Plant Ecology; Plant Sciences; Respiration; Seasonal variation; Seasons; Snow; Snow depth; Soil depth; Soil moisture; Soil surfaces; Special Feature: Original Article; Studies; Summer; Terrestrial ecosystems; Tree Biology; Variance analysis; Wind speed; Wind transfer; Winter
• ISSN: 1341-6979; 1610-7403
• DOI: 10.1007/s10310-012-0385-7

At the Takayama deciduous broadleaved forest Asiaflux site in Japan, the ecosystem carbon dynamics have been studied for more than two decades. In 2005, we installed non-dispersive infrared CO 2 sensors in the soil below the site's flux tower to systematically study vertical soil-air CO 2 dynamics and explain the behavior of soil surface CO 2 efflux. Soil-air CO 2 concentrations measured from June 2005 through May 2006 showed sinusoidal variation, with maxima in July and minima in winter, similar to the soil CO 2 effluxes measured simultaneously using open-flow chambers. Soil-air CO 2 concentrations increased with soil depth from 5 to 50 cm: from 2,000 to 8,000 ppm in the summer and from 2,000 to 3,000 ppm in the winter under snow. Summer soil-air CO 2 concentrations were positively correlated with soil moisture on daily and weekly scales, indicating that the Oi, Oe, and A horizons, where decomposition is accelerated by high-moisture conditions, contributed substantially to CO 2 emissions. This result is consistent with the short residence time (about 2 h) of CO 2 in the soil and larger emissions in shallow soil layers based on our diffusion model. We revealed for the first time that soil-air CO 2 concentrations in winter were correlated with both snow depth and wind speed. CO 2 transfer through the snow was hundreds of times the gas diffusion rates in the soil. Our estimate of the CO 2 efflux during the snow-cover season was larger than previous estimates at TKY, and confirmed the important contribution of the snow-cover season to the site's carbon dynamics.