Variations in fine root biomass of trees and understory in 16 stands throughout Finland were examined and relationships to site and stand characteristics determined. Norway spruce fine root biomass varied between 184 and 370 g m(-2), and that of Scots pine ranged between 149 and 386 g m(-2). In northern Finland, understory roots and rhizomes (< 2 mm diameter) accounted for up to 50% of the stand total fine root biomass. Therefore, the fine root biomass of trees plus understory was larger in northern Finland in stands of both tree species, resulting in a negative relationship between fine root biomass and the temperature sum and a positive relationship between fine root biomass and the carbon:nitrogen ratio of the soil organic layer. The foliage:fine root ratio varied between 2.1 and 6.4 for Norway spruce and between 0.8 and 2.2 for Scots pine. The ratio decreased for both Norway spruce and Scots pine from south to north, as well as from fertile to more infertile site types. The foliage:fine root ratio of Norway spruce was related to basal area and stem surface area. The strong positive correlations of these three parameters with fine root nitrogen concentration implies that more fine roots are needed to maintain a certain amount of foliage when nutrient availability is low. No significant relationships were found between stand parameters and fine root biomass at the stand level, but the relationships considerably improved when both fine root biomass and stand parameters were calculated for the mean tree in the stand. When the northern and southern sites were analyzed separately, fine root biomass per tree of both species was significantly correlated with basal area and stem surface area per tree. Basal area, stem surface area and stand density can be estimated accurately and easily. Thus, our results may have value in predicting fine root biomass at the tree and stand level in boreal Norway spruce and Scots pine forests.

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Effect of wood ash fertilization on soil chemical properties and stand nutrient status and growth of some coniferous stands in Finland .The effects of wood ash or wood ash plus nitrogen (N) fertilization on soil chemical properties, needle nutrient concentrations and tree growth were studied in five coniferous stands, aged 31 Á/75 yrs, after 5 and 10 yrs. In each experiment 3 t ha (1 of loose wood ash was applied to three replicated plots (30 )/30 m). In three of the experiments 120 Á/150 kg N ha (1 was applied together with the same wood ash (WAN). These three experiments also included a stand-specific fertilization (SSF) treatment, which consisted of 120, 150 or 180 kg N ha (1 . Five years after wood ash or WAN application the pH increase in the humus layer was 1 Á/1.7 pH-units and in the 0 Á/5 cm mineral soil layer 0.3 Á/0.4 pH-units. The increase was approximately the same 10 yrs after application, and was also associated with an increase in pH in the 5 Á/10 cm mineral soil layer. Wood ash or WAN significantly increased both the total and extractable calcium and magnesium concentrations in the humus layer on all the sites. Wood ash or WAN had an increasing effect on the boron concentrations, but a decreasing effect on the manganese concentrations in the needles. Wood ash had no significant effect on the volume growth. The trees on the WAN plots grew as well as or slightly better than those on the SSF plots.

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