Soil CO<sub>2</sub> efflux of a larch forest in northern Japan
We had continuously measured soil CO<sub>2</sub> efflux (<i>R</i><sub>s</sub>) in a larch forest in northern Japan at hourly intervals for the snow-free period in 2003 with an automated chamber system and partitioned <i>R</i><sub>s</sub> in...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2010-11-01
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| Series: | Biogeosciences |
| Online Access: | http://www.biogeosciences.net/7/3447/2010/bg-7-3447-2010.pdf |
| Summary: | We had continuously measured soil CO<sub>2</sub> efflux (<i>R</i><sub>s</sub>) in a larch forest in northern Japan at hourly intervals for the snow-free period in 2003 with an automated chamber system and partitioned <i>R</i><sub>s</sub> into heterotrophic respiration (<i>R</i><sub>h</sub>) and autotrophic respiration (<i>R</i><sub>r</sub>) by using the trench method. In addition, we applied the soil CO<sub>2</sub> concentration gradients method to continuously measure soil CO<sub>2</sub> profiles under snowpack in the snowy period and to partition <i>R</i><sub>s</sub> into topsoil (O<sub>a</sub> and A horizons) CO<sub>2</sub> efflux (<i>F</i><sub>t</sub>) with a depth of 0.13 m and sub-soil (C horizon) CO<sub>2</sub> efflux (<i>F</i><sub>c</sub>). We found that soil CO<sub>2</sub> effluxes were strongly affected by the seasonal variation of soil temperature but weakly correlated with soil moisture, probably because the volumetric soil moisture (30–40% at 95% confidence interval) was within a plateau region for root and microbial activities. The soil CO<sub>2</sub> effluxes changed seasonally in parallel with soil temperature in topsoil with the peak in late summer. On the other hand, the contribution of <i>R</i><sub>r</sub> to <i>R</i><sub>s</sub> was the largest at about 50% in early summer, when canopy photosynthesis and plant growth were more active. The temperature sensitivity (<i>Q</i><sub>10</sub>) of <i>R</i><sub>r</sub> peaked in June. Under snowpack, <i>R</i><sub>s</sub> was stable until mid-March and then gradually increased with snow melting. <i>R</i><sub>s</sub> summed up to 79 gC m<sup>−2</sup> during the snowy season for 4 months. The annual <i>R</i><sub>s</sub> was determined at 934 gC m<sup>−2</sup> y<sup>−1</sup> in 2003, which accounted for 63% of ecosystem respiration. The annual contributions of <i>R</i><sub>h</sub> and <i>R</i><sub>s</sub> to <i>R</i><sub>s</sub> were 57% and 43%, respectively. Based on the gradient approach, <i>R</i><sub>s</sub> was partitioned vertically into litter (O<sub>i</sub> and O<sub>e</sub> horizons) with a depth of 0.01–0.02 m, topsoil and sub-soil respirations with proportions of 6, 72 and 22%, respectively, on an annual basis. The vertical distribution of CO<sub>2</sub> efflux was consistent with those of soil carbon and root biomass. |
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| ISSN: | 1726-4170 1726-4189 |