Influence of Vegetation and Hydrology on the Humus Budgets of Labrador Lakes

A mass-balance approach is used to explore the effect of several hydrologic and geographic variables on humic matter concentrations in surface waters of Labrador–Ungava. Water-color measurements from 67 dilute oligotrophic lakes are used to evaluate model predictions of aquatic humus concentration from basin hydrology, catchment vegetation, and internal loss rates. The major trend in water color in the Labrador region — increasing north to south — results from differences in external humus loading from catchment vegetation and soils. Hydrologic influences on aquatic humus concentrations reside in the dilution of catchment drainage by direct precipitation to the lake — effective only when catchments are small — and in water residence time which controls losses due to mineralization and sedimentation.

[1]  D. P. Larsen,et al.  Phosphorus Retention Capacity of Lakes , 1976 .

[2]  S. A. Visser,et al.  Seasonal changes in the concentration and colour of humic substances in some aquatic environments , 1984 .

[3]  A. J. Stewart,et al.  Influence of dissolved humic materials on carbon assimilation and alkaline phosphatase activity in natural algal‐bacterial assemblages , 1982 .

[4]  James D. Allert,et al.  Acid deposition and watershed characteristics in relation to lake chemistry in northeastern Minnesota , 1985 .

[5]  J. Shapiro.  Chemical and Biological Studies on the Yellow Organic Acids of Lake Water1 , 1957 .

[6]  C. Brosset.  Factors influencing pH in lake water , 1979 .

[7]  C. Cronan,et al.  Chemistry and transport of soluble humic substances in forested watersheds of the Adirondack Park, New York , 1985 .

[8]  D. Schindler.  A Hypothesis to Explain Differences and Similarities Among Lakes in the Experimental Lakes Area, Northwestern Ontario , 1971 .

[9]  C. Driscoll,et al.  Partitioning Light Attenuation in an Acidic Lake , 1985 .

[10]  Barry G. Oliver,et al.  The contribution of humic substances to the acidity of colored natural waters , 1983 .

[11]  E. Tipping,et al.  Aggregation of aquatic humic substances , 1984 .

[12]  J. E. Samdal,et al.  Humic Substances in Water and the Effect of Impoundment , 1968 .

[13]  J. Giesy,et al.  STIMULATION OF GROWTH IN SCENEDESMUS OBLIQUUS (CHLOROPHYCEAE) BY HUMIC ACIDS UNDER IRON LIMITED CONDITIONS 1, 2 , 1976 .

[14]  F. Ugolini,et al.  Biopedological origin of peatlands in South East Alaska , 1979, Nature.

[15]  Charles T. Driscoll,et al.  Effect of aluminium speciation on fish in dilute acidified waters , 1980, Nature.

[16]  H. Ferguson,et al.  Mean Evaporation over Canada , 1970 .

[17]  R. Hecky,et al.  Depression of Primary Productivity by Humic Matter in Lake and Reservoir Waters of the Boreal Forest Zone , 1980 .

[18]  E. Tipping,et al.  Seasonal variations in the concentrations of humic substances in a soft‐water lake1 , 1983 .

[19]  J. Kerekes.  Limnological Conditions in Five Small Oligotrophic Lakes in Terra Nova National Park, Newfoundland , 1974 .