Liming of wetlands in the acidified Lake Roynelandsvatn catchment in southern Norway: Effects on stream water chemistry

In 1990, wetlands and blanket bogs, constituting 4.0% of the catchment of Lake Roynelandsvatn in southern Norway, were limed by helicopter with 20 t . ha(-1) of fine-powdered limestone. Liming caused a rapid increase in stream pH and calcium (Ca) and a decrease in reactive and inorganic monomeric aluminium (Al). Three years later the reactive Al concentration was still 50% lower and the Ca concentration twice as high as preliming values. Mean and minimum acid neutralizing capacity of the outlet stream were 23 and 8 mu equiv.. L(-1), respectively, and although pH had decreased to 5.2-5.3 the water quality was acceptable for the survival of brown trout (Salmo trutta). No significant increase in stream nitrate, organic nitrogen, or total organic carbon was measured after liming. Terrestrial liming may be a useful approach to neutralize acidic runoff because of the retention of inorganic monomeric Al in the catchment, the long-lasting increase in Ca concentration, and the inherent deacidification capacity during stormflows and snowmelt. Liming of strategic discharge areas in the catchment may limit the extent of undesirable effects, such as the death of Sphagnum mosses, on the terrestrial ecosystem.