title: Dual, differential isotope labeling shows the preferential movement of labile plant constituents into mineral-bonded soil organic matter.
abstract: The formation and stabilization of soil organic matter (SOM) are major concerns in the context of global change for carbon sequestration and soil health. It is presently believed that lignin is not selectively preserved in soil and that chemically labile compounds bonding to minerals comprise a large fraction of the SOM. Labile plant inputs have been suggested to be the main precursor of the mineral-bonded SOM. Litter decomposition and SOM formation are expected to have temperature sensitivity varying with the lability of plant inputs. We tested this framework using dual (13) C and (15) N differentially labeled plant material to distinguish the metabolic and structural components within a single plant material. Big Bluestem (Andropogon gerardii) seedlings were grown in an enriched (13) C and (15) N environment and then prior to harvest, removed from the enriched environment and allowed to incorporate natural abundance (13) C-CO2 and (15) N fertilizer into the metabolic plant components. This enabled us to achieve a greater than one atom % difference in (13) C between the metabolic and structural components within the plant litter. This differentially labeled litter was incubated in soil at 15 and 35 °C, for 386 days with CO2 measured throughout the incubation. After 14, 28, 147, and 386 days of incubation, the soil was subsequently fractionated. There was no difference in temperature sensitivity of the metabolic and structural components with regard to how much was respired or in the amount of litter biomass stabilized. Only the metabolic litter component was found in the sand, silt, or clay fraction while the structural component was exclusively found in the light fraction. These results support the stabilization framework that labile plant components are the main precursor of mineral-associated organic matter.
authors.affiliation: Natural Resource Ecology Laboratory, Colorado State University, 200 West Lake Street, Fort Collins, CO, 80523-1499, USA.
authors.forename: Michelle L
authors.initials: ML
authors.lastname: Haddix
authors.affiliation: Natural Resource Ecology Laboratory, Colorado State University, 200 West Lake Street, Fort Collins, CO, 80523-1499, USA.|Department of Soil and Crop Sciences, Colorado State University, 200 West Lake Street, Fort Collins, CO, 80523-1499, USA.
authors.forename: Eldor A
authors.initials: EA
authors.lastname: Paul
authors.affiliation: Natural Resource Ecology Laboratory, Colorado State University, 200 West Lake Street, Fort Collins, CO, 80523-1499, USA.|Department of Soil and Crop Sciences, Colorado State University, 200 West Lake Street, Fort Collins, CO, 80523-1499, USA.
authors.forename: M Francesca
authors.initials: MF
authors.lastname: Cotrufo
mesh_terms: D031722:Andropogon / Q000737:chemistry*; D002245:Carbon Dioxide / Q000032:analysis; D002247:Carbon Isotopes / Q000032:analysis; D005308:Fertilizers; D006812:Humic Substances; D007553:Isotope Labeling; D008903:Minerals / Q000737:chemistry*; D009587:Nitrogen Isotopes / Q000032:analysis; D012987:Soil / Q000737:chemistry*
chemical_list: D002247:Carbon Isotopes; D005308:Fertilizers; D006812:Humic Substances; D008903:Minerals; D009587:Nitrogen Isotopes; D012987:Soil; D002245:Carbon Dioxide
keywords: Q
  10-q; andropogon gerardii; differential isotopic labeling; litter decomposition; microbial efficiency-matrix stabilization; soil organic matter stabilization; stabilization efficiency; temperature sensitivity