Carbon isotopic fractionation in subtropical brazilian grassland soils. Comparison with tropical forest soils |
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Authors: | B Volkoff C C Cerri |
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Institution: | (1) ORSTOM, Paris, France;(2) CENA, Piracicaba, Brazil |
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Abstract: | The natural relationship13C/12C determined in three soil profiles under grass vegetation indicated a depletion in organic13C at depth: theδ
13C was between −18‰ and −15‰ in the A horizons and ranged from −18 to −22‰ at depth. Previous work showed that in forest soils,
whereδ
13C was near −28‰ in the upper horizon, there was, on the contrary, a relative enrichment of the lower strata. This meant thatδ
13C, initially different in the various topsoils, became more equal at depth. Comparison between dark, deep horizons (sombric
horizons), which are certainly of illuvial origine, would confirm this:δ
13C of grassland and a forest sombric horizon were almost equal at around −22‰. These results might mean that, in natural ecosystems,
the isotopic carbon composition of the soil underlying humus would be independent of the vegetation type. This would have
practical implications for the use of13C as a tracer for soil organic matter studies. |
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Keywords: | soil humus sombric horizons stable carbon isotope subtropical soils |
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