Breathing Soils: Topographic and Biologic Controls on Seasonal Soil CO2 Respiration in a Rocky Mountain Subalpine Meadow
- Type of resource
- Date created
- [ca. April 01, 2016-June 14, 2019]
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Honors theses written by undergraduates in the Stanford University School of Earth, Energy & Environmental Sciences. Theses provided courtesy of Stanford University Libraries. If you have questions, please contact the Branner Earth Sciences Library & Map Collections at firstname.lastname@example.org.
- Digital collection
- 28 digital items
- McCormick, Maeve Eilis Claire
- Primary advisor
- Maher, Katherine
- Sperling, Erik
- Chadwick, K. Dana
- Degree granting institution
- Stanford University, Department of Geological Sciences
Soil carbon accounts for roughly 80 percent of carbon in terrestrial ecosystems. Respiration of carbon dioxide (CO2) from plant roots and soil organisms is one of the largest fluxes of CO2 from the land surface to the atmosphere (Lal, 2008). Increasing temperatures and changes in the timing and amount of precipitation can potentially affect soil moisture, temperature, plant primary productivity, and microbial productivity. Measurements of the response of soil respiration to climate change forcings are often based on point measurements, then extrapolated to the landscape scale without much consideration of small-scale variation. Although both root and microbial soil CO2 respiration are known to be sensitive to changes in temperature and soil moisture, relationships derived from either point measurements (meter-scale) or laboratory experiments have not been tested over larger spatial domains (kilometer-scale), where competing factors may interact with the relationships observed at smaller scales. To determine how CO2 fluxes vary across scales, I examined the relationship between soil CO¬2 respiration and landscape metrics of soil moisture, such as topographic wetness index (TWI), across a subalpine meadow in the Colorado Rockies (East River, CO) from late May through August 2016. To identify the scales of spatial and temporal variation in soil properties (moisture and temperature) that have been found to control soil CO2 fluxes, I measured surface soil moisture and CO2 respiration rate at spatial scales of 0.5-40 m across a grid of 74 points within a 625 m^2 area of meadow-dominated hillslope. The magnitude of variability in both soil moisture and respiration slightly increased later in the growing season, but remained consistently small for spatial separations <50 m. Soil CO2 respiration is not well correlated with soil moisture. Further, neither soil moisture nor soil CO2 respiration correlate with TWI, indicating that this metric of topography does not capture the key drivers for either at our site. Expanding upon these observations, I used remotely-sensed multispectral data to determine that soil respiration is not correlated with plant primary productivity as represented by the Normalized Difference Vegetation Index (NDVI). Combining these observations, I found that the limited correlations between soil respiration and topographic or multispectral indices present challenges for extrapolating meter-scale measurements of soil moisture, temperature, and respiration to the catchment scale (km).
- Preferred Citation
- McCormick, Maeve E. C. 2019. Breathing Soils: Topographic and Biologic Controls on Seasonal Soil CO2 Respiration in a Rocky Mountain Subalpine Meadow. Stanford Digital Repository. Available at: https://purl.stanford.edu/rp520mb1905
- Related Publication
- Liu Y., Winnick M.J., Hsu H.T., Lawrence C.R., Maher K., Druhan J.L. (in press) Modeling transient soil moisture limitations on microbial carbon respiration. Journal of Geophysical Research – Biogeosciences.
- McCormick, M. E., M. Winnick, G. R. Rainaldi, C. R. Lawrence, J. L. Druhan, Hsiao-Tieh H., and K. Maher. 2016. Abstract B33B-0599: Spatial and Temporal Variability of Soil Respiration Fluxes from Alpine and Subalpine Soils in the East River Watershed, Colorado. American Geophysical Union Fall Meeting, San Francisco, CA.
- Winnick, M. J., C. R. Lawrence, M. McCormick, J. L. Druhan, and K. Maher. In review. Plant Phenology Modulation of Soil Respiration Pulse Behavior in a Montane Meadow, East River, Colorado, USA.
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