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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Plant and soil 67 (1982), S. 73-79 
    ISSN: 1573-5036
    Keywords: Models ; N-budgets ; N-inputs ; N-Losses ; Tropics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Description / Table of Contents: Resumen Los balances regionales de nitrógeno son útiles para estimar el estado del conocimiento sobre el ciclo de nitrógeno en los ecosistemas mas importantes de la región, para enfocar los flujos y reservas regionales en perspectiva y para adentrarse en los procesos que regulan tanto los ciclos regionales como los globales. Los balances regionales existentes se han utilizado para estudiar la contaminación de aguas freáticas con nitratos y para identificar aquellos ecosistemas localmente improtantes desde el punto de vista del uso de la tierra pero que son poco conocidos biogeoquímicamente. Algunos problemas que son comunes a muchos balances son: la selección de compartimientos inapropiados, documentación inadecuada y la certeza injustificada. Aun cuando sean imprecisos, los balances en gran escala, en el estado actual del conocimiento, aportan a investigadores y a quienes manjean los sistemas, algunas ventajas importantes que no estarían disponibles de otro modo.
    Notes: Abstract Regional nitrogen budgets are useful for assessing what is known about nitrogen cycling in important ecosystems of a region, for placing the various regional fluxes and pools into perspective, and for providing insight into the processes that regulate both regional and global nitrogen cycling. Existing regional budgest have been used both to study groundwater nitrate pollution and to help identify local ecosystems that are important on a land-use basis but that are poorly described biogeochemically. Avoidable problems common to many budgets include inappropriate compartment components, inadequate documentation, and unjustified certainty. Though imprecise, large-scale nutrient budgets at our present stage of understanding offer to researchers and system managers important advantages that would otherwise not be available.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Plant and soil 67 (1982), S. V 
    ISSN: 1573-5036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1573-515X
    Keywords: N15 ; nitrogen ; nutrient cycling ; plants ; stable isotopes ; soil ; temperate forest ; tropical forest
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Several lines of evidence suggest that nitrogen in most tropical forests is relatively more available than N in most temperate forests, and even that it may function as an excess nutrient in many tropical forests. If this is correct, tropical forests should have more open N cycles than temperate forests, with both inputs and outputs of N large relative to N cycling within systems. Consequent differences in both the magnitude and the pathways of N loss imply that tropical forests should in general be more15N enriched than are most temperate forests. In order to test this hypothesis, we compared the nitrogen stable isotopic composition of tree leaves and soils from a variety of tropical and temperate forests. Foliar δ15N values from tropical forests averaged 6.5‰ higher than from temperate forests. Within the tropics, ecosystems with relatively low N availability (montane forests, forests on sandy soils) were significantly more depleted in15N than other tropical forests. The average δ15N values for tropical forest soils, either for surface or for depth samples, were almost 8‰ higher than temperate forest soils. These results provide another line of evidence that N is relatively abundant in many tropical forest ecosystems.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1573-5036
    Keywords: Forest soils ; Nitrogen cycling ; Nitrogen loss ; N2 ; N2O
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary We examined denitrification and nitrous oxide (N2O) production in intact soil cores removed from a clearcut southern pine site subjected to different harvest, site preparation, and herbicide treatments. Rates of N2O production in structurally intact soil cores incubated with acetylene showed that clearcutting stimulated denitrification but that rates varied by sample date and post-harvest site treatment. The site was harvested in December 1980. In September 1982 denitrification was greater in sheared, piled and disked (SPD) plots than in chopped or reference (uncut) plots; the following May, rates were higher in seven of the eight treatment plots than in the reference plot, and were highest in three of the four herbicide-treated plots. On both sample dates denitrification rates were correlated with nitrification potentials and nitrate pool sizes in the plots, and nitrate added to cores from all treatments significantly stimulated denitrification. Nitrate supply thus appeared to regulate denitrification at this site. Relative to harvest or site preparation losses of nitrogen, denitrification is not a major vector of N loss at this coniferous site; under post-harvest conditions, however, denitrification may be of the same magnitude as leaching losses.
    Type of Medium: Electronic Resource
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