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Résumé :
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Current agricultural practices are responsible for the deposition of large quantities of nutrients to lakes and streams. As the quantity of fertilizer applied often exceeds soil storage capacity, excess nutrients may be discharged from the surface and subsurface into lakes and streams. Riparian forests have been shown to filter some nutrients from agricultural runoff and subsurface flow. We measured nutrient stores and extractability in each season on three sites in surface organic litter and the top 10 cm of mineral soil to compare the buffering capacity of riparian soils supporting forest and grassland vegetation. In all seasons, greater total amounts of nutrients were immobilized in forest surface litter than in grassland surface litter, and greater amounts of NH4+ NO3- P, Ca, Mg, Mn, and Fe were extracted. In the forest, more total N, P, K, Mg, and Zn were found in the surface organic litter in autumn than in other seasons; amounts in grassland did not vary with season.
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