Nieminen, M. 2004. Export of dissolved organic carbon, nitrogen and phosphorus following clear-cutting of three Norway spruce forests growing on drained peatlands in southern Finland. Silva Fennica 38(2): 123-132. The effect of clear-cutting on the concentrations of dissolved organic carbon (DOC), organic nitrogen (DON), NH 4 + , NO 3 -, and P in outflow water from three productive, Norway spruce dominated drained peatlands (R CC , V CC-1 , V CC-2 ) were studied. Changes in runoff and transport

more »

... loads (concentration × runoff) at two of the catchments during the frost-free period are also presented. Approximately 40% of the area was cut at R CC and V CC-2 , and 72% at V CC-1 . The volume removed was 250 m 3 ha -1 at R CC , 259 m 3 ha -1 at V CC-1 , and for V CC-2 , 317 m 3 ha -1 . The mean annual increase in outflow concentrations of DOC during the first four years after clear-cutting was 9.0 mg l -1 at R CC , 22.8 mg l -1 at V CC-1 and 8.4 mg l -1 at V CC-2 . Corresponding increases in the forms of nitrogen were: 0.23, 0.51 and 0.16 mg DON l -1 ; 0.06, 0.31 and 0.04 mg NH 4 + -N l -1 ; and 0.05, 0.12 and 0.22 mg NO 3 --N l -1 . Clear-cutting did not significantly (p > 0.05) increase P concentrations. The increase in non-frost season runoff over the first three years after clear-cutting was 107 mm at R CC and 207 mm at V CC-1 . The export loads of DOC during the nonfrost season increased by 80 kg ha -1 at R CC and by 184 kg ha -1 at V CC-1 over the first three years. Corresponding increases for the other studied solutes were: 1.78 and 3.98 kg DON ha -1 ; 0.39 and 1.49 kg NH 4 +_ N ha -1 ; 0.45 and 0.48 kg NO 3 --N ha -1 , and 0.09 and 0.06 kg P ha -1 . The study demonstrated that clear-cutting may significantly increase the export of DOC and different forms of nitrogen from drained productive peatlands while only small increases in phosphorus export may occur.