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Title: The Millennial model: in search of measurable pools and transformations for modeling soil carbon in the new century

Soil organic carbon (SOC) can be defined by measurable chemical and physical pools, such as mineral-associated carbon, carbon physically entrapped in aggregates, dissolved carbon, and fragments of plant detritus. Yet, most soil models use conceptual rather than measurable SOC pools. What would the traditional pool-based soil model look like if it were built today, reflecting the latest understanding of biological, chemical, and physical transformations in soils? We propose a conceptual model—the Millennial model—that defines pools as measurable entities. First, we discuss relevant pool definitions conceptually and in terms of the measurements that can be used to quantify pool size, formation, and destabilization. Then, we develop a numerical model following the Millennial model conceptual framework to evaluate against the Century model, a widely-used standard for estimating SOC stocks across space and through time. The Millennial model predicts qualitatively similar changes in total SOC in response to single factor perturbations when compared to Century, but different responses to multiple factor perturbations. Finally, we review important conceptual and behavioral differences between the Millennial and Century modeling approaches, and the field and lab measurements needed to constrain parameter values. Here, we propose the Millennial model as a simple but comprehensive framework to model SOCmore » pools and guide measurements for further model development.« less
ORCiD logo [1] ;  [2] ;  [3] ;  [4] ;  [5] ;  [6] ;  [7] ;  [8] ;  [9] ;  [1] ; ORCiD logo [10]
  1. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Climate and Ecosystem Sciences Division
  2. San Diego State Univ., San Diego (United States). Biology Dept.
  3. Colorado State Univ., Fort Collins, CO (United States). Natural Resource Ecology Lab.
  4. Argonne National Lab. (ANL), Argonne, IL (United States). Biosciences Division; Univ. of Illinois, Chicago, IL (United States). Dept. of Biological Sciences
  5. Univ. of Oklahoma, Norman, OK (United States). Dept. of Microbiology and Plant Biology
  6. Univ. of Maryland, Frostburg, MD (United States). enter for Environmental Science, and Appalachian Lab.
  7. Boston Univ., MA (United States). Dept. of Biology and PhD Program in Biogeoscience
  8. Univ. of Toledo, OH (United States). Dept. of Environmental Sciences
  9. Univ. of California, Santa Barbara, CA (United States). Dept. of Ecology, Evolution and Marine Biology
  10. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Environmental Science Division & Climate Change Science Inst.
Publication Date:
Grant/Contract Number:
Accepted Manuscript
Journal Name:
Additional Journal Information:
Journal Volume: 137; Journal Issue: 1-2; Journal ID: ISSN 0168-2563
Research Org:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org:
Country of Publication:
United States
59 BASIC BIOLOGICAL SCIENCES; Modeling; Soil carbon; Organic matter; Microbial activity; Decomposition; Global change
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