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Dual, differential isotope labeling shows the preferential movement of labile plant constituents into mineral‐bonded soil organic matter
Author(s) -
Haddix Michelle L.,
Paul Eldor A.,
Cotrufo M. Francesca
Publication year - 2016
Publication title -
global change biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 4.146
H-Index - 255
eISSN - 1365-2486
pISSN - 1354-1013
DOI - 10.1111/gcb.13237
Subject(s) - chemistry , soil organic matter , organic matter , environmental chemistry , detritus , plant litter , litter , context (archaeology) , lability , biomass (ecology) , silt , incubation , soil carbon , agronomy , nutrient , soil water , ecology , biology , organic chemistry , paleontology , biochemistry
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– CO 2 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 CO 2 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.