Modeling the seasonality of belowground respiration along an elevation gradient in the western Chugach Mountains, Alaska
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Belowground respiration is typically the largest flux of carbon from terrestrial ecosystems to the atmosphere, making up >70% of total respiration in boreal forests. Recent work has shown that belowground respiration continues during the snow-covered season in boreal ecosystems, but few studies have made complementary measurements during the snow-free season and it remains uncertain what proportion of annual belowground respiration occurs during winter. Traditional models of the relationship between temperature and respiration assume fixed temperature sensitivity, but it has become clear that the apparent temperature sensitivity of belowground respiration increases as soils approach 0°C. Use of fixed temperature sensitivity to model carbon budgets of northern ecosystems may, therefore, yield misleading results. We measured belowground respiration monthly over 2 years in four ecosystems along an elevation gradient in south-central Alaska. Three models, representing different hypotheses about the relationship between temperature and respiration, were confronted with the data. A logistic model, which allows the temperature sensitivity to vary inversely with temperature, and a variation of the Q10 model, which allows the temperature sensitivity to vary seasonally, performed well at all sites and produced similar estimates of seasonal and annual belowground respiration. The traditional Q10 model performed poorly at all sites and overestimated respiration during the snow-covered season. Annual belowground respiration was generally greater than in ecosystems of interior Alaska, where winters are colder and summers are warmer and drier. Belowground respiration during the snow-covered season made up 6–15% of the annual total—a small, but sensitive, component of annual carbon budgets.
KeywordsAIC Boreal Maximum likelihood Snow Soil respiration Winter
This project was supported by National Science Foundation grants ANT-0528748 and ARC-0909155 to PS and an award from the University of Alaska Anchorage Chancellor’s Fund to JW. We thank Chugach State Park for permission to work on Wolverine Peak.
- Akitaya E (1974) Studies on depth hoar. Contrib Inst Low Temp Sci 26A:1–67Google Scholar
- Bolstad PV, Davis KJ, Martin J, Cook BD, Wang W (2004) Component and whole-system respiration fluxes in northern deciduous forests. Tree Physiol 24:493–504Google Scholar
- Burnham KP, Anderson DR (2002) Model selection and multi-model inference: a practical information-theoretic approach, 2nd edn. Springer, New YorkGoogle Scholar
- Cable JM, Ogle K, Lucas RW et al (2010) The temperature responses of soil respiration in deserts: a seven desert synthesis. Biogeochemistry. doi: 10.1007/s10533-010-9448-z
- Flanagan PW, Veum AK (1974) Relationships between respiration, weight loss, temperature and moisture in organic residues on tundra. In: Holding AJ, Heal OW, Maclean SF Jr, Flanagan PW (eds) Soil organisms and decomposition in tundra. Tundra Biome Steering Committee, Stockholm, pp 249–277Google Scholar
- Massman WJ, Sommerfeld RA, Zeller K, Hehn T, Hudnell L, Rochelle SG (1995) CO2 flux through a Wyoming seasonal snowpack: diffusional and pressure pumping effects. Biogeochemistry of snow-covered catchments. International Association of Hydrological Sciences, Wallingford, pp 71–79Google Scholar
- McDowell NG, Marshall JD, Hooker TD, Musselman R (2000) Estimating CO2 flux from snowpacks at three sites in the Rocky Mountains. Tree Physiol 20:745–753Google Scholar
- McGuire AD, Mellilo JM, Randerson JT, Parton WJ, Heimann M, Meier RA, Clein JS, Kicklighter DW, Sauf W (2000) Modeling the effects of snowpack on heterotrophic respiration across northern temperate and high latitude regions: comparison with measurements of atmospheric carbon dioxide in high latitudes. Biogeochemistry 48:91–114CrossRefGoogle Scholar
- Raich JW, Schlesinger WH (1992) The global carbon dioxide flux in soil respiration and its relationship to vegetation and climate. Tellus 44B:81–99Google Scholar
- Richardson AD, Hollinger DY (2005) Statistical modeling of ecosystem respiration using eddy covariance data: maximum likelihood parameter estimation, and Monte Carlo simulation of model and parameter uncertainty, applied to three simple models. Agric For Meteorol 131:191–208Google Scholar
- Sullivan PF (2009) Snow distribution, soil temperature and late winter CO2 efflux from soils near the Arctic treeline in northwest Alaska. Biogeochemistry. doi: 10.1007/s10533-009-9390-0