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  • 1995-1999  (3)
  • dissolved organic carbon (DOC)  (2)
  • Biomass increase  (1)
  • 1
    ISSN: 1573-515X
    Keywords: climate change ; dissolved organic carbon (DOC) ; forested catchments ; nutrient export ; Precambrian Shield streams ; storm runoff
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Dissolved organic carbon (DOC) concentrations and DOC export arestudied during storms to examine the relationship between DOCconcentration and stream discharge and to assess the importance of stormson DOC export. Storms were monitored in seven subcatchments within twosmall watersheds (Harp 4--21 and Harp 3A) on the Precambrian Shield inCentral Ontario, Canada. Stream DOC concentrations increase during stormsby as much as 100% and 410% in Harp3A and Harp 4--21 respectively. The seasonal regression between DOC andstream discharge is significant in subcatchments without wetlands(r2 〉 0.7) but is not significant in thetwo subcatchments with small wetland areas (r2 〈0.06). On average, regressions based on weekly data yield accurate estimatesof DOC export but the variation in regressions among individual storms andthe small number of high DOC samples result in uncertainties of more than30% in DOC export. The period-weighted calculation ofDOC export from weekly data underestimates export by 14%and 22% in Harp 3A and Harp 4--21 respectively. Stormswere responsible for 57% to 68% of theDOC export in the autumn and 29% to 40%of the DOC export in the spring. A single large storm accounted for31% of the autumn DOC export in Harp 3A. The importanceof individual storms for DOC export and the variation in the relationshipbetween DOC and stream discharge among storms make it difficult to predictthe effects of climate change on DOC export and DOC concentrations.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-515X
    Keywords: carbon cycling ; dissolved organic carbon (DOC) ; forested catchments ; nutrient export ; Precambrian Shield streams ; storm runoff
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Dissolved organic carbon (DOC) concentrations and export were studied in two small catchments in central Ontario to examine DOC sources and to assess the hypothesis that organic matter adjacent to the stream is a significant contributor of DOC during storms. Different DOC dynamics and exports were observed according to the depth of the riparian water table. In Harp 4-21, riparian flowpaths were predominantly through A and upper B soil horizons and riparian soils contributed between 73 and 84% of the stream DOC export during an autumn storm. In Harp 3A, riparian flowpaths were predominantly through lower B horizons. Consequently, riparian soils were less important and hillslopes contributed more than 50% of the stream DOC export in subcatchments without wetlands during storms. Wetlands and adjacent soils contributed significantly to DOC export in Harp 3A; 8% of the total catchment area exported 32 to 46% of the storm runoff DOC. DOC export dynamics in wetlands and riparian soils were distinctly different. In wetlands, transport was affected by leaching and flushing of DOC at the wetland surface leading to lower DOC concentrations with successive storms. In riparian soils, groundwater flowpaths were more important and stronger positive relationships between discharge and DOC concentration were observed. Precipitation, throughfall and stemflow were minor sources of stream DOC during storms and contributed less than 20% of the total export.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Plant cell, tissue and organ culture 45 (1996), S. 67-72 
    ISSN: 1573-5044
    Keywords: Biomass increase ; chromosome count ; growth regulators ; regeneration ; tissue culture ; wormwood
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Callus cultures were initiated from micropropagated Artemisia absinthium plantlets on MS basal medium supplemented with different concentrations of BA, Kn, NAA, IAA and 2,4-d in combination or singly. Supplementing the medium with low doses of both BA in combination with NAA, and Kn in combination with NAA enhanced the growth rate of callus cultures. However, cultures grew slowly following the second subculture and the majority turned brown and died within the next month. Initiation of root and shoot primordia occured directly from leaf explants cultured on 1.81 μM 2,4-d, while adventitious shoot formation from callus was observed occasionally when BA was added to the medium in combination with IAA. Furthermore, medium containing 2.22 μM BA and 2.69 μM NAA stimulated both callus growth and organogenesis on some callus cultures derived from leaves and stems of young stock material. The best results were obtained with leaf explants. Cytological analysis of root meristems revealed that all regenerants were diploid (2n=18), as expected.
    Type of Medium: Electronic Resource
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