The effect of industrial aerial pollution on the composition of soil solutions in podzols

The composition of soil solutions is a sensitive indicator of the technogenic transformation of podzols of the Kola Peninsula under the impact of aerial pollution. The soil solutions have been obtained using Rhizon vacuum samplers. A sharp rise in the concentrations of heavy metals and sulfates is registered in the solutions from polluted soils. The leaching of organic substances, potassium, sodium, calcium, magnesium, manganese, and zinc from the litter horizons of polluted soils considerably increases. The ratios between the element concentrations in solutions from the litter horizons to those from the illuvial horizons become narrower, which suggests that the litter has partly lost its barrier function.     

Population and biomass of microorganisms in soils of pyrogenic succession in the northern taiga pine forests

In the organic horizons of the Al-Fe-humus podzols under the old pine forests of the northern taiga, the biomass of all the groups of microorganisms, the length of the fungal and actinomycete mycelium, the number of fungal spores, and the bacterial population were maximal (13 mg/g) irrespectively of the stage of pyrogenic succession. The share of fungi (mainly, of basidiomycetes) exceeded 90%. In the mineral root-inhabited soil horizons, the biomass of microorganisms was not greater than 1.0 mg/g. The soil under the lichen pine forest had the smallest biomass of microorganisms as compared to the soil under the pine forests that were not exposed to fire for a long time. At all the stages of the pyrogenic succession, the most favorable conditions for the functioning of microorganisms were in the root-inhabited horizons of the soils in near-stem sites due to the accumulation of nutrients there. In the soils of these zones, the basidiomycete biomass was greater than that in the soils of the gaps. In the mineral soil horizons, buckleless micromycetes demonstrated the same trend. No distinct parcella differences, with respect to the soil nutrient regime, were found only for the prokaryotes. The fungi in the Al-Fe-humus podzols may be used as indicators for the pyrogenic succession stages of forest ecosystems. At the early stages, micromycetes without buckles prevailed, and, in the course of succession, the share of basidiomycetes clearly increased. The density and structure of mycorrhiza were tightly related to the nutrient regime of the soils. The increase in the concentration of available biogenic elements in the root-inhabited soil horizons did not cause the necessity of developing complex mycorrhiza forms.     

Acidity of podzolic soils subjected to sulphur pollution near a Cu-Ni smelter at the Kola Peninsula

The acidity of the podzolic soils in coniferous forests on the northern tree line (Kola Peninsula) subjected to severe sulphur pollution is considered. The pH values of precipitation were positively correlated with the distance from the pollution point source. There was also a correlation between base saturation of the organic horizon and distance. The long-term SO₂-emissions have resulted in the higher leachability of base cations and dissolution of fulvic acids in the humus horizon. In polluted areas the flux of H⁺ from the organic layer could be stronger owing to higher proportion of hydrolysable humus compounds. Inputs of H⁺ from the atmosphere and humus horizon have resulted in the higher concentrations of the exchangeable aluminium in the illuvial horizon.     

Population and biomass of soil microorganisms in old-growth primary spruce forests in the Northern Taiga

The number and biomass of microorganisms in the soils under lichen, grass-bilberry, and grass spruce forests of old age were studied on the Kola Peninsula. The dry biomass of microorganisms in the organic soil horizons was shown to reach 28 mg/g with a predominance (96 to 99%) of micromycetes. At tree trunk sites, in the organic horizons of all the soils studied, where the contents of organic carbon and mineral nutrients were higher, the number and biomass of all the groups of microorganisms was lower than in those in the soils of the gaps. The factors limiting the functioning of microorganisms in the soils under spruce tree crowns are thought to be the high acidity of the water flowing down the tree trunks and the high phenol content in it. In the mineral horizons of the soils, the patterns of the microorganisms were opposite: in all the spruce forests, the fungal biomass was the highest in the soils of the trunk zones, as well as the bacterial population and biomass in the grass spruce forest. In the latter, the maximal length of the actinomycete mycelium was also recorded in the soil of the trunk zones with the elevated contents of carbon and mineral nutrients.