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Stable Carbon Isotopic Composition of Carbonate in Holocene Grassland Soils
Author(s) -
Kelly Eugene F.,
Amundson Ronald G.,
Marino Bruno D.,
DeNiro Michael J.
Publication year - 1991
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1991.03615995005500060025x
Subject(s) - carbonate , pedogenesis , soil water , organic matter , geology , soil organic matter , environmental chemistry , chemistry , mineralogy , soil science , organic chemistry
Stable C isotope ratios ( 13 C/ 12 C) and amounts of soil carbonate were measured at six sites of differing temperature, moisture, and vegetational make‐up in the northern Great Plains of the USA in order to determine climatic and biotic influences on the stable C isotope chemistry of these soils. With approximately constant precipitation, total carbonate decreased with increasing temperature. With decreasing precipitation, the total carbonate in the soils increased. For all but one soil, the 13 C/ 12 C ratios of segregated carbonate conformed to values expected if the carbonate formed from CO 2 derived from soil organic matter. In the nonconforming site, the 13 C/ 12 C ratios of the carbonate suggest that the vegetation and soil organic matter have recently become dominated by C 4 plants, which use the Hatch‐Slack photosynthetic pathway, and organic matter derived from them. The 13 C/ 12 C ratios of disseminated carbonate reflect the proportion of pedogenic and parent‐material carbonate in the sample. The 13 C/ 12 C ratios of pure, pedogenic carbonate at each site could be constrained by: (i) measured 13 C/ 12 C ratios of soil organic matter, (ii) measured 13 C/ 12 C ratios of carbonate nodules, and (iii) calculated 13 C/ 12 C ratios using a diffusion model designed by others. Estimates of the percentages of disseminated pedogenic carbonate in the soils suggested that, as the amount of weathering at sites increases and the total carbonate decreases, the percentage of carbonate that remains becomes more dominated by carbonate of pedogenic origin.