Quantifying the effect of petrogenic carbon on SOC turnover for two Rocky Mountain soils: When are petrogenic carbon corrections required?

Journal of Geophysical Research: Biogeosciences
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Abstract

Petrogenic organic carbon (OCpetro), derived from sedimentary rocks, is an often overlooked and poorly quantified source of soil organic carbon (SOC), which may influence measured or modeled SOC composition, age, and stability. In this study, we exploited differences in thermochemical stability between OCpetro and biogenic SOC (OCbio) using stepped elemental analysis to quantify the fractional contribution of OCpetro to total SOC (fpetro), and we conducted a sensitivity analysis to estimate the effects of OCpetro on modeled SOC transit times and system ages. Specifically, we compared the effects of accounting for OCpetro inputs in SOC turnover modeling (using SoilR) for two montane meadow soils that are underlain by Cretaceous Mancos Shale. At these sites, we estimate that OCpetro comprises 7%–9% of the total SOC stock (fpetro = 0.07–0.09). However, accounting for OCpetro as a mixture of inert and passive C or as completely inert C had negligible effects on SOC transit times and system ages, suggesting that there is a threshold of OCpetro content under which there is minimal effect on calculated SOC turnover. Based on our sensitivity analysis, we estimate this threshold to be fpetro = 0.125, further supporting that the accurate calculation of OCpetro remains an important factor in estimating SOC turnover.

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Publication type Article
Publication Subtype Journal Article
Title Quantifying the effect of petrogenic carbon on SOC turnover for two Rocky Mountain soils: When are petrogenic carbon corrections required?
Series title Journal of Geophysical Research: Biogeosciences
DOI 10.1029/2023JG007838
Volume 130
Issue 2
Year Published 2025
Language English
Publisher American Geophysical Union
Contributing office(s) Geosciences and Environmental Change Science Center
Description e2023JG007838, 16 p.
Country United States
State Colorado
Other Geospatial Elk Mountains
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