Pulse Emissions of Carbon Dioxide during Snowmelt at a High-Elevation Site in Northern Arizona, U.S.A.

Abstract

The paradigm that winter is a dormant period of soil biogeochemical activity in high elevation or high latitude ecosystems has been amply refuted by recent research. Carbon dioxide (CO₂) released from cold or snow-covered soil is a substantial component of total annual ecosystem carbon fluxes. Recent investigations have shown that the late-winter/early-spring transition is a period of high biogeochemical activity. However, little is known about the temporal dynamics of CO₂ from the snowpack itself during periods of snowmelt. We present a case study of three snowmelt events at a high-elevation site in northern Arizona during which we measured changes in CO₂ concentrations and fluxes above the snow and within the soil profile, and characterized the soil physical environment and site meteorological variables. We show that large pulses of CO₂ were emitted to the atmosphere during snowmelt, and we present evidence that these pulses came from CO₂ stored in snowpack. Earlier and more frequent snowmelts worldwide caused by climate change have the potential to alter the timing of release of CO₂ from land to atmosphere.

Acknowledgments

This research was supported by a grant from the North American Carbon Program/USDA CREES NRI (2004-35111-15057), and the National Science Foundation MRI program (DBI-0216471). Sullivan was supported by the Mission Research Program at the Northern Arizona University School of Forestry (McIntire-Stennis/AZ Bureau of Forestry) and an NSFIGERT fellowship (DGE-0549505). We would like to thank B. Hungate and three reviewers for helpful comments on this manuscript and P. Templer and J. Schimel for organizing an oral session at the 94th ESA Annual Meeting where Sullivan first presented these data.