Biomasses of ectomycorrhiza] and saprotrophic fungal communities partitioned into sporophores and nonreproductive structures were estimated in mature Scots pint {Pinus sylvestris L.) stands along an urban nitrogen and sulphur pollution gradient in northern Finland. The average total biomass of fungi varied in the four pollution zones from 14-6 to 202 g d. w t kg"' soil d. wt and from 73'3 to 1080 g d. wi m"^. tht mycelia of both mycorrhizal and saprotrophic fungi in the soil comprising 72 8O'\, of the total. The annual carbon allocation to the fungal communities was calculated to vary between 9 and 26 "^ of the estimated annual carbon assimilation at the Scots pine sites. The size of tbe mean fungal biomass fractions decreased in the following sequence: mycelia in the soil > fungal biomass in fine roots estimated in terms of chitin > sclerotia > fungal biomass in fine roots estimated in terms of ergosterol > sporophores of mycorrhiza! fungi > sporopbores of saprotrophic fungi. A positive correlation was obtained between the number of Scots pine mycorrhiza and the a\'erage sporophore yield of mycorrhiziil fungi for three auecesaive yeaTS. The sporophore biomass ot" the mycorrhizal fungi was smaller at the most polluted than at the least polluted sites. The total fungal biomass allocation was not affected by urban pollution.

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Abstract. The biological activity and the amount of living fungal mycelium in the mor humus of pine forests around an industrialized city were studied. The activities were lower in the more polluted zone than in a cleaner one but varied between sites within the zones. The relationship of these activities to the microbial environment was determined in both the total data and in the various zones separately. Soil respiration rate was positively related to ammonium nitrogen concentration of the humus in the less polluted zone but negatively in the more polluted zone, while it related negatively to total nitrogen concentration of the humus in the entire data set. DHA was partly accounted for by the variation in acidity parameters, and best by pH(CaCl,), with a positive relation. The length of FDA active fungal mycelium showed no significant variation between the zones or sites, and was thus poorly explained by the environmental variables. The weather conditions prevailing at two seasons did not explain any variation of the activities or the length of FDA mycelium, though the biological variables were in general positively related to the moisture of the humus.