Deep-rooted perennials alter microbial respiration and chemical composition of carbon in density fractions along soil depth profiles
Kyungjin Min,
Erin Nuccio,
Eric Slessarev,
Megan Kan,
Karis J. McFarlane,
Erik Oerter,
Anna Jurusik,
Gregg Sanford,
Kurt D Thelen,
Jennifer Pett-Ridge,
Asmeret Asefaw Berhe
Affiliations
Kyungjin Min
Department of Agricultural Biotechnology, Seoul National University, Seoul 08826, South Korea; Research Institute of Agriculture and Life Sciences, Seoul National University, Seoul 08826, South Korea; Department of Life and Environmental Sciences, University of California, Merced, CA 95343, USA; Corresponding authors at: Department of Agricultural Biotechnology, Seoul National University, Seoul 08826, South Korea (K. Min).
Erin Nuccio
Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, CA 94550, USA; Corresponding authors at: Department of Agricultural Biotechnology, Seoul National University, Seoul 08826, South Korea (K. Min).
Eric Slessarev
Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, CA 94550, USA; Department of Ecology and Evolutionary Biology, Yale University, New Haven, CT 06511, USA; Yale Center for Natural Carbon Capture, Yale University, New Haven, CT 06511, USA
Megan Kan
Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, CA 94550, USA
Karis J. McFarlane
Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, CA 94550, USA
Erik Oerter
Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, CA 94550, USA
Anna Jurusik
Department of Life and Environmental Sciences, University of California, Merced, CA 95343, USA
Gregg Sanford
Department of Soil and Environmental Sciences, University of Wisconsin – Madison, Madison, WI 53706, USA
Kurt D Thelen
Department of Plant, Soil & Microbial Sciences, Michigan State University, East Lansing, MI 48824, USA
Jennifer Pett-Ridge
Department of Life and Environmental Sciences, University of California, Merced, CA 95343, USA; Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, CA 94550, USA
Asmeret Asefaw Berhe
Department of Life and Environmental Sciences, University of California, Merced, CA 95343, USA
Growing deep-rooted perennials has been proposed to increase soil organic carbon (SOC) stocks and mitigate CO2 emissions. Yet, we know little about the bioavailability and chemical properties of SOC under deep-rooted perennials and shallow-rooted annuals. Improving our understanding of the role of deep-rooted perennials for belowground C storage is critical, as root growth has the potential to both increase SOC stock and accelerate loss of existing SOC. Here, we assessed the effects of >10 years of land conversion from shallow-rooted annuals (maize) to deep-rooted perennials (switchgrass) on SOC bioavailability (microbial respiration, Δ14C-CO2), mineral-associated SOC (density fractionation), and SOC turnover and composition (14C-SOC, DRIFT spectroscopy) in surface soils (0–20 cm) and subsoils (90–120 cm) at two sites with sandy and silty soils. We demonstrate that switchgrass enhanced microbial respiration of recently-fixed C in surface soils. Switchgrass increased Δ14C values of the free light fraction in subsoil of the sandy site, by supplying aliphatic C (putative simple plant C) into the soil. In contrast, maize input less root C into the soil, and at one site increased the decomposition of older SOC, which indicates that overall microbial C demand outpaced plant C inputs. These results highlight that deep-rooted perennials stimulate the transfer of more atmospheric C to both surface and subsoils than shallow-rooted annuals, that newly generated SOC under deep-rooted perennials is relatively less protected from decomposition, and that reaping the C benefits of deep-rooted perennials could require maintaining the land cover as a perennial cropping system.
