title: Protection of soil carbon within macro-aggregates depends on intra-aggregate pore characteristics.
abstract: Soil contains almost twice as much carbon (C) as the atmosphere and 5-15% of soil C is stored in a form of particulate organic matter (POM). Particulate organic matter C is regarded as one of the most labile components of the soil C, such that can be easily lost under right environmental settings. Conceptually, micro-environmental conditions are understood to be responsible for protection of soil C. However, quantitative knowledge of the specific mechanisms driving micro-environmental effects is still lacking. Here we combined CO2 respiration measurements of intact soil samples with X-ray computed micro-tomography imaging and investigated how micro-environmental conditions, represented by soil pores, influence decomposition of POM. We found that atmosphere-connected soil pores influenced soil C's, and especially POM's, decomposition. In presence of such pores losses in POM were 3-15 times higher than in their absence. Moreover, we demonstrated the presence of a feed-forward relationship between soil C decomposition and pore connections that enhance it. Since soil hydrology and soil pores are likely to be affected by future climate changes, our findings indicate that not-accounting for the influence of soil pores can add another sizable source of uncertainty to estimates of future soil C losses.
authors.affiliation: Department of Plant, Soil and Microbial Sciences, Michigan State University, East Lansing, Michigan, United States of America.
authors.forename: Alexandra N
authors.initials: AN
authors.lastname: Kravchenko
authors.affiliation: IASS-Global Soil Forum, Institute for Advanced Sustainability Studies, Potsdam, Germany.
authors.forename: Wakene C
authors.initials: WC
authors.lastname: Negassa
authors.affiliation: Department of Plant, Soil and Microbial Sciences, Michigan State University, East Lansing, Michigan, United States of America.
authors.forename: Andrey K
authors.initials: AK
authors.lastname: Guber
authors.affiliation: Center for Advanced Radiation Sources, The University of Chicago, Argonne National Lab, Argonne, Illinois, United States of America.
authors.forename: Mark L
authors.initials: ML
authors.lastname: Rivers