Carbon dioxide emissions from exhumed petrocalcic horizons

TitleCarbon dioxide emissions from exhumed petrocalcic horizons
Publication TypeJournal Article
Year of Publication2006
AuthorsSerna-Perez A., H. Monger C, Herrick JE, Murray L.W.
JournalSoil Science Society of America Journal; Pedology, Forest Range and Wildland Soils
Volume70
Pagination795-805
Date PublishedMay 2006
Accession NumberJRN00440
ARIS Log Number170959
KeywordsCO2, emissions, exhumed petrocalcic horizons, IRGA, pedogenic carbonate, soils
Abstract

The second largest pool of terrestrial carbon is pedogenic CaCO3. In addition to being an important sink of atmospheric CO2, pedogenic carbonate has the potential to be an important source of atmospheric CO2. The cemented form of pedogenic carbonate (the petrocalcic horizon) develops in geomorphically stable soil in arid, semiarid, and various subhumid climates. In many of these dryland areas, such as the Chihuahuan Desert of North America, erosion has stripped away overlying soil and exhumed the petrocalcic horizon, thereby lifting it into a weathering zone above the calcification zone where it normally forms. This research tested the hypothesis that Aridisols with exhumed petrocalcic horizons will emit more CO2 than neighboring noneroded Aridisols with petrocalcic horizons or neighboring Entisols. We tested this hypothesis by comparing the amount of CO2 and the delta 13C of CO2 released from the three soil types. Using a randomized complete block design, CO2 emissions were measured using NaOH and soda lime traps from June 2002 to October 2003. Neither NaOH traps nor soda lime traps detected any statistical difference in cumulative CO2 emissions from the three soil types at the P = 0.05 level. Moreover, the isotopic analysis of CO2 did not match the isotopic values of pedogenic carbonate nor were there any statistical differences (p = 0.05) in delta 13C of CO2 among the three soil types. We conclude, therefore, that exhumed petrocalcic horizons are not actively emitting CO2 at a rate significantly greater than adjacent soils; and thus, carbon stored in petrocalcic horizons can be considered a recalcitrant reservoir within the decadal timeframe pertinent to carbon sequestration policies.

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