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

Capturing spatial heterogeneity of soil carbon under changing climate

January 31, 2017

Spatial heterogeneity of the land surface modulates the magnitude of energy, moisture, and greenhouse gas exchanges with the atmosphere. However, representing land surface spatial heterogeneity when designing observation schemes is a critical scientific challenge.

Researchers led by EVS developed a geospatial approach that utilizes the multivariate spatial heterogeneity of soil-forming factors to identify an optimal number and spatial distribution of observation sites to improve soil organic carbon (SOC) stock estimates under current and future climatic conditions. By using the environmental data expected to influence soil formation as a proxy for the heterogeneity of SOC stocks, the scientists determined that complementing existing SOC samples with 484 new observation sites would be needed to characterize whole-profile SOC stocks across Alaska at a confidence interval of 5 kg C m-2. Estimation of SOC stocks to depths of 0-1 m and 0-2 m with the same level of confidence would require 309 and 446 new observation sites, respectively. The study found that depending upon the projected emission scenarios of Intergovernmental Panel on Climate Change; 12 to 41 additional sites would be needed to capture the impact of future climate on Alaskan SOC stocks by 2100.

The observation sites identified in this study represent spatially distributed locations across Alaska that capture the multivariate heterogeneity of soil-forming factors under current and future climatic conditions. This information is needed to 1) guide new field observations intended to reduce existing uncertainty in SOC observations, and 2) create robust spatial benchmarks to evaluate Earth System Model results.

This study has been accepted for publication in the Journal of Geophysical Research – Biogeosciences. The article is entitled “Observational needs for estimating Alaskan soil carbon stocks under current and future climate,” by U.W.A. Vitharana, U. Mishra, J.D. Jastrow, R. Matamala, and Z. Fan (doi:10.1002/2016JG003421, 2017).

Black dots show the distribution of 906 observation sites across Alaska that characterizes the multivariate spatial heterogeneity of soil-forming factors.
Black dots show the distribution of 906 observation sites across Alaska that characterizes the multivariate spatial heterogeneity of soil-forming factors. [Source: Umakant Mishra, Argonne National Laboratory]
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portrait of Umakant Mishra