Belowground allocation and dynamics of recently fixed plant carbon in a California annual grassland

Plant roots and the organisms that surround them are a primary source for stabilized soil organic carbon (SOC). While grassland soils have a large capacity to store organic carbon (C), few field-based studies have quantified the amount of plant-fixed C that moves into soil and persists belowground o...

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Bibliographic Details
Published in:Soil biology & biochemistry 2021-12, Vol.165
Main Authors: Fossum, Christina, Estera-Molina, Katerina Y., Yuan, Mengting, Herman, Donald J., Chu-Jacoby, Ilexis, Nico, Peter S., Morrison, Keith D., Pett-Ridge, Jennifer, Firestone, Mary K.
Format: Article
Language:English
Subjects:
13C-NMR
13CO2 pulse labeling
annual grassland
BASIC BIOLOGICAL SCIENCES
ENVIRONMENTAL SCIENCES
GEOSCIENCES
soil organic matter
SOM
SOM density fractionation
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Summary:Plant roots and the organisms that surround them are a primary source for stabilized soil organic carbon (SOC). While grassland soils have a large capacity to store organic carbon (C), few field-based studies have quantified the amount of plant-fixed C that moves into soil and persists belowground over multiple years. Yet this characteristic of the soil C cycle is critical to C storage, soil water holding capacity, nutrient provisions, and the management of soil health. Here, we tracked the fate of plant-fixed C following a five-day 13CO2 labeling of a Northern California annual grassland, measuring C pools starting at the end of the labeling period, at three days, four weeks, six months, one year, and two years. Soil organic carbon was fractionated using a density-based approach to separate the free-light fraction (FLF), occluded-light fraction (OLF), and heavy fraction (HF). Using isotope ratio mass spectrometry, we measured 13C enrichment and total C content for plant shoots, roots, soil, soil dissolved organic carbon (DOC), and the FLF, OLF, and HF. The chemical nature of C in the HF was further analyzed by solid state 13C nuclear magnetic resonance (NMR) spectroscopy.
ISSN:0038-0717
1879-3428