Caitlin E. Hicks Pries Corey Lawrence Craig Rasmussen Susan E. Crow Alison M. Hoyt Sophie F. von Fromm Zheng Shi Shane Stoner Casey McGrath Jeffery 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 Katherine Heckman 2022 <div class="abstract-group"><div class="article-section__content en main"><p>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&nbsp;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&nbsp;cm). The relationship of C abundance (mg C g⁻¹&nbsp;soil) to climate varied among pools and with depth. Mineral-associated C in surface soils (&lt;30&nbsp;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.</p></div></div> application/pdf 10.1111/gcb.16023 en Wiley Beyond bulk: Density fractions explain heterogeneity in global soil carbon abundance and persistence article