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Research article2022Peer reviewed

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

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

Published in

Global Change Biology
2022, Volume: 28, number: 3, pages: 1178-1196 Publisher: WILEY

    Sustainable Development Goals

    SDG13 Climate action
    SDG15 Life on land

    UKÄ Subject classification

    Soil Science

    Publication identifier

    DOI: https://doi.org/10.1111/gcb.16023

    Permanent link to this page (URI)

    https://res.slu.se/id/publ/115055