Environmental Science Division (EVS)a Division of Argonne National Laboratory

Spatial scaling changes environmental controls and spatial heterogeneity of soil carbon stocks

August 6, 2015

EVS researcher, Umakant Mishra, recently published a journal article in Biogeosciences entitled “Scaling impacts on environmental controls and spatial heterogeneity of soil organic carbon stocks.” Spatial heterogeneity of the land surface affects energy, moisture, and greenhouse gas exchanges with the atmosphere. However, representing heterogeneity of terrestrial hydrological and biogeochemical processes in earth system models (ESMs) remains a critical scientific challenge. DOE/BER researchers used soil profile observations, environmental factors (such as topography, climate, land cover types, surficial geology) and geospatial modeling to study the impact of spatial scaling on environmental controls, spatial structure, and statistical properties of soil organic carbon (SOC) stocks in Alaska.

The study found that different environmental factors were significant predictors of SOC stocks at different spatial scales. Of the 19 environmental factors evaluated, only elevation, temperature, potential evapotranspiration, and scrub land cover types were significant predictors at all investigated scales. The strengths by which these four environmental variables controlled SOC stocks decreased with increasing scale. The spatial structure of SOC stocks also changed with scale. The spatial heterogeneity of predicted SOC stocks decreased with spatial scale over the range of 50 m to ~500 m, and remained constant beyond this scale. Moderately-accurate linear relationships were found between the mean and other statistical properties of predicted SOC stocks. Current ESMs operate at coarse spatial scales (50-100 km) and are therefore unable to represent environmental controllers and spatial heterogeneity of high-latitude SOC stocks in a manner consistent with observations.

Improved knowledge of the scaling behavior of environmental controls and statistical properties of SOC stocks is critical for ESM land model benchmarking and ultimately might enable the spatial heterogeneity of soil biogeochemistry to be represented at scales finer than those currently resolved by ESMs.

Citation: Mishra, U., and W.J. Riley. 2015. Scaling impacts on environmental controls and spatial heterogeneity of soil organic carbon stocks. Biogeosciences 12:3993-4004, doi:10.5194/bg-12-3993-2015.

Variance of soil organic carbon stocks as a function of spatial scale. Each dot is predicted variance of SOC stock at each spatial scale across Alaska.
Variance of soil organic carbon stocks as a function of spatial scale. Each dot is predicted variance of SOC stock at each spatial scale across Alaska. [Source: Umakant Mishra, Argonne National Laboratory]
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portrait of Umakant Mishra