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.
Min, Kyungjin, et al. "Deep-rooted perennials alter microbial respiration and chemical composition of carbon in density fractions along soil depth profiles." Geoderma, vol. 455, Feb. 2025. https://doi.org/10.1016/j.geoderma.2025.117202
Min, Kyungjin, Nuccio, Erin, Slessarev, Eric, et al., "Deep-rooted perennials alter microbial respiration and chemical composition of carbon in density fractions along soil depth profiles," Geoderma 455 (2025), https://doi.org/10.1016/j.geoderma.2025.117202
@article{osti_2520214,
author = {Min, Kyungjin and Nuccio, Erin and Slessarev, Eric and Kan, Megan and McFarlane, Karis J. and Oerter, Erik and Jurusik, Anna and Sanford, Gregg and Thelen, Kurt D. and Pett-Ridge, Jennifer and others},
title = {Deep-rooted perennials alter microbial respiration and chemical composition of carbon in density fractions along soil depth profiles},
annote = {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.},
doi = {10.1016/j.geoderma.2025.117202},
url = {https://www.osti.gov/biblio/2520214},
journal = {Geoderma},
issn = {ISSN 0016-7061},
volume = {455},
place = {United States},
publisher = {Elsevier},
year = {2025},
month = {02}}
Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)
Sponsoring Organization:
Korea Environmental Industry & Technology Institute (KEITI); National Research Foundation of Korea (NRF); National Science Foundation (NSF); USDA; USDOE; USDOE Laboratory Directed Research and Development (LDRD) Program; USDOE National Nuclear Security Administration (NNSA); USDOE Office of Science (SC), Biological and Environmental Research (BER)