CGRG Bibliography of Canadian Geomorphology
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Author : Gagnier, D.L.; and Bailey, R.C.
Date : 1994
Title : Balancing loss of information and gains in efficiency in characterizing stream sediment samples.
Publication : Journal of the North American Benthol. Society
Issue : 13(2):
Page(s) : 170-180
Abstract
Sediment description is becoming an essential consideration in many types of lotic research. This paper examines the necessity for detailed organic loss-on-ignition measures and inorganic particle-size-analysis in describing streambed sediment samples. Sediment samples (n = 94) were obtained from a 150-m stretch of the Madawaska River in central Ontario, and a full analysis (organic content and inorganic particle-size-analysis) of each sediment sample was carried out. The difference between every pair of sample points in the composition of sediment was summarized in a distance matrix of average taxonomic distances. We quantified the loss of information about variation in benthic sediment habitat when organic content of the sediment was ignored, size fractions of sediment were pooled prior to analysis, and the presence or absence of size categories, rather than actual mass determinations, were used to describe sediment samples. Distance matrices were re-calculated with these cruder sediment descriptions, and Mantel's test was used to measure the correlation between distance matrices based on varying levels of resolution in sediment analysis. Also, a distance matrix was calculated which summarized the difference between pairs of sites in the total Ephemeroptera, Plecoptera, and Trichoptera emergence downstream of core removals. This matrix was also correlated, using Mantel's test, with distance matrices based on varying degrees of resolution in sediment analysis. The original detailed sediment description, with organic content present, was highly correlated with the detailed sediment description excluding organic content. Sediment descriptions with pooled sieves but actual mass of fractions were more highly correlated with the original, full description of the sediment than binary (presence/absence of size fractions) sediment descriptions. Variation among sampling points in insect emergence was also more highly correlated with sediment data using actual mass measures than sediment descriptions using only presence/absence data. Both sieve reduction methods suggested in our paper retain most of the original sediment-sample information important in explaining the variation in emerging insects. The usefulness of pooling sieve categories and recording only the presence or absence of size fraction categories to future sediment characterizations will depend on the extent to which the original sediment information is retained in the new characterizations.
Bibliography of Canadian Geomorphology