Beyond bulk: Density fractions explain heterogeneity in global soil carbon abundance and persistence

Katherine Heckman; Caitlin E Hicks Pries; Corey R Lawrence; Craig Rasmussen; Susan E Crow; Alison M Hoyt; Sophie F von Fromm; Zheng Shi; Shane Stoner; Casey McGrath; Jeffrey Beem-Miller; Asmeret Asefaw Berhe; Joseph C Blankinship; Marco Keiluweit; Erika Marín-Spiotta; J Grey Monroe; Alain F Plante; Joshua Schimel; Carlos A Sierra; Aaron Thompson; Rota Wagai

doi:10.1111/gcb.16023

Beyond bulk: Density fractions explain heterogeneity in global soil carbon abundance and persistence

Glob Chang Biol. 2022 Feb;28(3):1178-1196. doi: 10.1111/gcb.16023. Epub 2021 Dec 16.

Authors

Katherine Heckman¹, Caitlin E Hicks Pries², Corey R Lawrence³, Craig Rasmussen⁴, Susan E Crow⁵, Alison M Hoyt^{6

7}, Sophie F von Fromm^{6

8}, Zheng Shi⁹, Shane Stoner^{6

8}, Casey McGrath⁵, Jeffrey Beem-Miller⁶, Asmeret Asefaw Berhe¹⁰, Joseph C Blankinship⁴, Marco Keiluweit¹¹, Erika Marín-Spiotta¹², J Grey Monroe¹³, Alain F Plante¹⁴, Joshua Schimel¹⁵, Carlos A Sierra^{6

16}, Aaron Thompson¹⁷, Rota Wagai¹⁸

Affiliations

¹ USDA Forest Service, Northern Research Station, Houghton, Michigan, USA.
² Department of Biological Sciences, Dartmouth College, Hanover, New Hampshire, USA.
³ U.S. Geological Survey, Geosciences and Environmental Change Science Center, Denver, Colorado, USA.
⁴ Department of Environmental Science, University of Arizona, Tucson, Arizona, USA.
⁵ Natural Resources and Environmental Management Department, University of Hawaii Manoa, Honolulu, Hawaii, USA.
⁶ Department of Biogeochemical Processes, Max-Planck-Institute for Biogeochemistry, Jena, Germany.
⁷ Climate and Ecosystem Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California, USA.
⁸ Department of Environmental Systems Science, ETH Zurich, Zurich, Switzerland.
⁹ Computational Sciences & Engineering Division and Climate Change Science Institute, Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA.
¹⁰ Department of Life and Environmental Sciences, University of California, Merced, California, USA.
¹¹ School of Earth & Sustainability and Stockbridge School of Agriculture, University of Massachusetts, Amherst, Massachusetts, USA.
¹² Department of Geography, University of Wisconsin-Madison, Madison, Wisconsin, USA.
¹³ Department of Plant Sciences, University of California, Davis, Davis, California, USA.
¹⁴ Department of Earth & Environmental Science, University of Pennsylvania, Philadelphia, PA, USA.
¹⁵ Department of Ecology Evolution and Marine Biology, University of California Santa Barbara, Santa Barbara, California, USA.
¹⁶ Department of Ecology, Swedish University of Agricultural Sciences, Uppsala, Sweden.
¹⁷ Department of Crop and Soil Sciences and the Odum School of Ecology, University of Georgia, Athens, Georgia, USA.
¹⁸ Institute for Agro-Environmental Sciences, National Agriculture and Food Research Organization, Tsukuba, Ibaraki, Japan.

PMID: 34862692
DOI: 10.1111/gcb.16023

Abstract

Understanding the controls on the amount and persistence of soil organic carbon (C) is essential for predicting its sensitivity to global change. The response may depend on whether C is unprotected, isolated within aggregates, or protected from decomposition by mineral associations. Here, we present a global synthesis of the relative influence of environmental factors on soil organic C partitioning among pools, abundance in each pool (mg C g^-1 soil), and persistence (as approximated by radiocarbon abundance) in relatively unprotected particulate and protected mineral-bound pools. We show that C within particulate and mineral-associated pools consistently differed from one another in degree of persistence and relationship to environmental factors. Soil depth was the best predictor of C abundance and persistence, though it accounted for more variance in persistence. Persistence of all C pools decreased with increasing mean annual temperature (MAT) throughout the soil profile, whereas persistence increased with increasing wetness index (MAP/PET) in subsurface soils (30-176 cm). The relationship of C abundance (mg C g^-1 soil) to climate varied among pools and with depth. Mineral-associated C in surface soils (<30 cm) increased more strongly with increasing wetness index than the free particulate C, but both pools showed attenuated responses to the wetness index at depth. Overall, these relationships suggest a strong influence of climate on soil C properties, and a potential loss of soil C from protected pools in areas with decreasing wetness. Relative persistence and abundance of C pools varied significantly among land cover types and soil parent material lithologies. This variability in each pool's relationship to environmental factors suggests that not all soil organic C is equally vulnerable to global change. Therefore, projections of future soil organic C based on patterns and responses of bulk soil organic C may be misleading.

Keywords: climate change; persistence; radiocarbon; soil carbon; soil fractions; soil organic matter; terrestrial carbon cycle.

MeSH terms

Carbon*
Climate
Minerals
Soil*
Temperature

Substances

Minerals
Soil
Carbon