Canonical variables of aquatic bryophyte combinations for predicting water trophic level |
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Authors: | A Vanderpoorten R Palm |
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Institution: | (1) Unité de Zoologie Générale, Belgium;(2) Unité de Statistique et Informatique; Faculté, Universitaire des Sciences Agronomiques de Gembloux, 2, Passage des Déportés, B-5030 Gembloux, Belgium |
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Abstract: | Concentrations of soluble reactive phosphorus (SRP), nitrate, and soluble reactive silicon (SRSi) were monitored in 12 streams
draining small catchments (<10 km2) in the English Lake District. The catchments varied with respect to underlying geology,
soil type and land cover. Average concentrations of SRP were in the range 0.5–11.2 μg P l-1, and estimated loads ranged from
0.01 to 0.14 kg P ha-1 a-1. The higher concentrations and loads were associated with catchments containing improved pasture.
Mean streamwater concentrations of nitrate varied from 55 to 660 μg N l-1, while loads were in the range 0.8–9.6 kg N ha-1
a-1; no general dependence on catchment properties was discerned. Concentrations of SRSi were similar in all the streams (0.8–2
mg Si l-1), and annual loads were in the range 10–26 kg Si ha-1 a-1. Loads of all three nutrients were greatest during the
winter, because of higher discharges, but in some catchments containing improved pasture, considerable transport of P also
took place during the summer. Concentrations of nitrate in streams draining unimproved moorland catchments are approximately
twice those reported for samples taken from similar streams in 1973 and 1974, possibly because of increased atmospheric deposition
of inorganic nitrogen (ammonium and nitrate). Concentrations of SRP in such streams were similar to those reported for the
earlier samples. Comparisons of stream loads of SRP and nitrate with estimated inputs suggest that catchment soils retain
substantial amounts of these nutrients. Implications for surface water eutrophication of changes in P retention by soils are
discussed.
This revised version was published online in July 2006 with corrections to the Cover Date. |
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Keywords: | phosphorus nitrate silicon streams English Lake District |
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