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  • 1
    Electronic Resource
    Electronic Resource
    Carbon-13 variation with depth in soils of Brazil and climate change during the Quaternary (1996)
    Springer
    Oecologia 106 (1996), S. 376-381 
    Details
    ISSN: 1432-1939
    Keywords: Amazon ; Vegetation change ; Stable carbon isotope ; Radiocarbon ; Soil organic matter
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Paleoecological and geomorphological studies indicate that, during the middle Holocene, there was a predominance of drier conditions with grassy savannahs replacing forests across the South American continent. Modern savannahs are composed mainly of C4 plants and soils developed under this type of vegetation show enrichment in 13C compared to soils under C3 vegetation cover. If soils contain stabilized organic matter formed in the middle Holocene, we hypothesize that former C4 vegetation would be evidenced by a large enrichment of 13C in soil organic matter (SOM). We investigate this possibility examining the depth variation of carbon isotopic composition in 21 soil profiles collected by different researchers at 14 different sites in Brazil. Of these, profiles from only three sites showed a marked increase of 13C with depth (9–10‰ enrichment in δ13C difference between the surface soil and deepest depth); two sites showed intermediate enrichment (4–5‰), and nine sites showed a small enrichment of approximatelly 2.5‰. The majority of sites showing all-C3 derived SOM were in the Amazon region. Possible causes for the absence of a large 13C enrichment with depth are: (1) dominance of C3 rather than C4 grasses in mid-Holocene savannahas, (2) soil profiles did not preserve organic matter derived from mid-Holocene plants, (3) the retreat of forest areas did not occur on a regional scale, but was a much more localized phenomenon.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00334565
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Commentary: Carbon Metabolism of the Terrestrial Biosphere: A Multitechnique Approach for Improved Understanding (2000)
    Springer
    Ecosystems 3 (2000), S. 115-130 
    Details
    ISSN: 1435-0629
    Keywords: Key words: biosphere metabolism; carbon cycle; carbon fluxes; global change; terrestrial ecosystems.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: ABSTRACT Understanding terrestrial carbon metabolism is critical because terrestrial ecosystems play a major role in the global carbon cycle. Furthermore, humans have severely disrupted the carbon cycle in ways that will alter the climate system and directly affect terrestrial metabolism. Changes in terrestrial metabolism may well be as important an indicator of global change as the changing temperature signal. Improving our understanding of the carbon cycle at various spatial and temporal scales will require the integration of multiple, complementary and independent methods that are used by different research communities. Tools such as air sampling networks, inverse numerical methods, and satellite data (top-down approaches) allow us to study the strength and location of the global- and continental-scale carbon sources and sinks. Bottom-up studies provide estimates of carbon fluxes at finer spatial scales and examine the mechanisms that control fluxes at the ecosystem, landscape, and regional scales. Bottom-up approaches include comparative and process studies (for example, ecosystem manipulative experiments) that provide the necessary mechanistic information to develop and validate terrestrial biospheric models. An iteration and reiteration of top-down and bottom-up approaches will be necessary to help constrain measurements at various scales. We propose a major international effort to coordinate and lead research programs of global scope of the carbon cycle.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100210000014
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    Paper (German National Licenses)
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