The Millennial Model: In Search of Measurable Pools and Transformations for Modeling Soil Carbon in the New Century

The Science

Scientists at the Lawrence Berkeley National Laboratory (LBNL) built a new conceptual and numerical model—the Millennial model—that defines soil pools based on measurements. They evaluated how its predictions differ from the widely used Century model.

The Impact

This is the first model to use measurements of particulate organic matter (POM), aggregation, low molecular weight carbon (LMWC), and mineral-associated organic matter (MAOM) to reflect the latest understanding of biological, chemical, and physical transformations in soils.


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? A team led by LBNL propose a new conceptual model—the Millennial model—that defines pools as measurable entities. First, they discussed relevant pool definitions conceptually and in terms of the measurements that can be used to quantify pool size, formation, and destabilization. They then developed 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. Furthermore, they reviewed important conceptual and behavioral differences between the Millennial and Century modeling approaches, and the field and lab measurements needed to constrain parameter values. The Millennial model is proposed as a simple but comprehensive framework to model SOC pools and guide measurements for further model development.

Principal Investigator(s)

Rose Abramoff
Lawrence Berkeley National Laboratory

Related Links


The Carbon Cycle Interagency Working Group provided funding for the “Celebrating the 2015 International Decade of Soil — Understanding Soil’s Resilience and Vulnerability” workshop held at the University Corporation for Atmospheric Research in Boulder, Colo., USA on March 14–16, 2016. The University Corporation for Atmospheric Research provided meeting space. Lawrence Berkeley National Laboratory is managed and operated by the Regents of the University of California under contract DE-AC02-05CH11231 with the U.S. Department of Energy (DOE). Oak Ridge National Laboratory is managed by the University of Tennessee-Battelle, LLC, under contract DE-AC05-00OR22725 with DOE. Argonne National Laboratory is managed by University of Chicago Argonne, LLC, under contract DE-AC02-06CH11357 with DOE.


Abramoff, R.Z., X. Xu, M. Hartman, S. O’Brien, W. Feng, E.A. Davidson, A.C. Finzi, D. Moorhead, J. Schimel, M.S. Torn, M.A. Mayes. “The Millennial Model: In search of measurable pools and transformations for modeling soil carbon in the new century.” Biogeochemistry (early online publishing December 2017) 137, 51–71 (2018). [DOI:10.1007/s10533-017-0409-7]