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  • 1
    ISSN: 1573-5036
    Schlagwort(e): 13C isotope ; changes in soil ; forest clearing ; maize crop ; soil organic carbon
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract In southwest France, sandy spodosols have developed from Quaternary sandy eolian deposits. On these soils, numerous forest lands have been converted to continuous intensive maize cropping. A chronosequence study is realized by comparing organic C pools and 13C natural abundance of one forested and 6 agricultural sites, whose ages of cultivation range from 4 to 32 yr. δ13C ratio is found to increase with time of cultivation. After 3 decades of intensive maize cropping, about half of the initial organic C content in the forest topsoil layer has disappeared. The fraction of C derived from maize crop increases during the first decades of cultivation, but its level is significantly lower than those observed in other soils, which indicates a high mineralization rate of organic C. In this context, soil characteristics associated to intensive agricultural practices lead to a rapid and large loss of C, whereas inputs from maize seem to have only a very small long-term contribution.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Soil Science Society of America journal 62 (1998), S. 743-749 
    ISSN: 1435-0661
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: b from soil properties for soils across the Amazon basin. Bulk density values are needed to convert nutrient content and organic carbon (OC) content to weight of nutrient and OC per unit area; unfortunately, common field methods to measure Db are limited with regard to reliable, complete, and uniform soil data. Much effort has been made in finding alternative solutions to predict Db from soil properties. We hypothesized that Db could be reliable estimated by multiple regression of OC, soil textural properties, and some chemical properties. Using the data of 323 soils horizons from the Brazilian Amazon basin, a stepwise multiple regression (SMR) procedure was developed to predict Db from other soil properties. Multiple regression relationships were obtained for all the data, which were also partitioned by layer and then by main soil order: Latossolos (Oxisols, 62 horizons) and Podzólicos (Alfisols and Ultisols, 212 horizons). The SMR on all the data showed that clay content is the best predictor of Db accounting for 37% of the variation. Adding OC content increased the explained variance up to nearly 50%. Predictions of the models were improved when the data were partitioned by order and by horizon type. In the case of Latossolos (Oxisols), the use of OC and clay content as predictors increased the percentage of explained variation, reaching 71% using all layers and 79% for A horizons. The results of this study will provide a basis for estimating OC stocks in the Amazon basin.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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