C and N mineralization and earthworm populations in a Norway spruce forest at Hasslöv (SW Sweden), 25 years after liming

University essay from SLU/Dept. of Ecology

Abstract: During the last decades of the 20th century, acid rain affected many areas in Europe and NorthernAmerica. Soil acidification was considered a large problem for forest ecosystems, because it wasexpected that tree growth would be hampered by low pH, nutrient deficiencies and highconcentrations of free Al. Furthermore low soil pH can change the soil fauna and soil microbialbiomass. High acidity has also been shown to reduce C and N mineralization. Liming wasexpected to be a good measure against soil acidification. The present study assesses C and Nmineralization and the earthworm community in the Hasslöv forest (SW Sweden; Norwayspruce), 25 years after liming with a low dose of CaCO3 (1.75 t ha-1) and a low, medium andhigh dose (1.55, 3.45 and 8.75 t ha-1) of dolomitic lime.Soil pH correlated to the lime dose. Liming with medium and high doses of dolomitic limeincreased C mineralization rates in the FH layer and the upper mineral soil. Liming did notincrease N mineralization rates, though there was an increase in nitrification in the soil with thehighest dose of lime. The C and N pool were lower in the heavily limed soil and to a lesserextent in the medium limed soil, compared to the control soil, mostly due to a reduction in theorganic layer. Furthermore earthworm populations were larger with increasing doses of lime.The dominant species, Dendrobaena octaëdra, was present in all treatments whereas three otherspecies were only found in the highest doses.When extrapolated to the field, both C and N mineralization expressed on an area basis werelower in soils with the highest lime treatment than in the control, and N mineralization was alsolower in the medium limed soil. This can be explained by the fact that the C and N pools hadbeen markedly reduced and that the increases in mineralization rate per gram soil could not makeup for this reduction.In conclusion, addition of lime has long-lasting effects that can be seen as higher pH, higher Cand N mineralization rates, lower soil pools of C and N and higher abundances of earthwormsstill after 25 years from the liming event. We recommend that as a measure against acidityliming should only be used with great caution.

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