P. Kortelainen et S. Saukkonen, LEACHING OF NUTRIENTS, ORGANIC-CARBON AND IRON FROM FINNISH FORESTRY LAND, Water, air and soil pollution, 105(1-2), 1998, pp. 239-250
This study provides an assessment of the spatial variability of the lo
ng-term leaching of nutrients, total organic carbon (TOC) and iron (Fe
-tot) from 22 forested catchments (0.69-56 km(2)), distributed across
all but the northernmost areas of Finland. The natural, unmanaged Kruu
nuoja catchment is located in a national park, while the other catchme
nts represent Finnish forestry land. The average leaching of P-tot (4.
2 kg km(-2) yr(-1)) from the Kruunuoja catchment was small compared to
the catchments representing forestry land (on average 10 kg km(-2) yr
(-1)). Moreover, P fertilization was the most important predictor for
the spatial variation in P-tot leaching (r(2) = 0.45). Leaching of TOC
, Fe-tot and N compounds was not closely related to forestry practices
. Median C/N ratio in the study streams was high (range 34-66). The av
erage inorganic N proportion and leaching of NO3--N were lowest in the
Kruunuoja catchment (7.3 % and 2.8 kg km(-2) yr(-1), respectively) an
d highest in the southernmost Teeressuonoja catchment (54 % and 100 kg
km(-2) yr(-1), respectively) located in the highest N deposition area
. The most important forestry practices since the 1960's have affected
about 2.4 % of the area of study sites per year (cf. 2 % in the entir
e country in 1991). Moreover, the mean annual runoff from the catchmen
ts (230-430 mm yr(-1)) agrees with the mean annual runoff from Finland
(301 mm yr(-1)). Consequently, the results of the study catchments ca
n be used to estimate average total annual leaching from Finnish fores
try land: 2,700 t of P-tot, 48,000 t of N-tot, 110,000 t of Fe-tot and
1.5 million t of TOC.