Epsilon Archive for Student Projects

Abstract

During the last decades of the 20th century, acid rain affected many areas in Europe and Northern
America. Soil acidification was considered a large problem for forest ecosystems, because it was
expected that tree growth would be hampered by low pH, nutrient deficiencies and high
concentrations of free Al. Furthermore low soil pH can change the soil fauna and soil microbial
biomass. High acidity has also been shown to reduce C and N mineralization. Liming was
expected to be a good measure against soil acidification. The present study assesses C and N
mineralization and the earthworm community in the Hasslöv forest (SW Sweden; Norway
spruce), 25 years after liming with a low dose of CaCO3 (1.75 t ha-1) and a low, medium and
high 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 lime
increased C mineralization rates in the FH layer and the upper mineral soil. Liming did not
increase N mineralization rates, though there was an increase in nitrification in the soil with the
highest dose of lime. The C and N pool were lower in the heavily limed soil and to a lesser
extent in the medium limed soil, compared to the control soil, mostly due to a reduction in the
organic layer. Furthermore earthworm populations were larger with increasing doses of lime.
The dominant species, Dendrobaena octaëdra, was present in all treatments whereas three other
species were only found in the highest doses.

When extrapolated to the field, both C and N mineralization expressed on an area basis were
lower in soils with the highest lime treatment than in the control, and N mineralization was also
lower in the medium limed soil. This can be explained by the fact that the C and N pools had
been markedly reduced and that the increases in mineralization rate per gram soil could not make
up for this reduction.

In conclusion, addition of lime has long-lasting effects that can be seen as higher pH, higher C
and N mineralization rates, lower soil pools of C and N and higher abundances of earthworms
still after 25 years from the liming event. We recommend that as a measure against acidity
liming should only be used with great caution.