Soil microflora in an area where spruce ( Picea abies) was killed by SO 2 emissions and was succeeded by birch ( Betula pendula) and mountain ash ( Sorbus aucuparia)

Abstract

The spruce forests ( Picea abies L. Karst.) in North Bohemia, Czech Republic, died under the influence of SO 2 emissions. We observed (1988–1989) that the number of heterotrophic soil bacteria decreased in the decomposition horizons under the dead spruce trees, compared with the situation under healthy spruce forest. The number of micromycetes increased as a result of the influence of acid rain. The biochemical activity of soil microbes was reduced. The breakdown of cellulose and the oxidation of thiosulphate decreased as did respiration and ammonification. After the demise of spruce forests the groundflora developed and pioneer trees like birch ( Betula pendula Rath.) and mountain ash ( Sorbus aucuparia L.) took over. The grasses produced enormous amounts of eexudates and the leaf litter of new vegetation was well decomposed. There were ample nutrients for soil microflora. The microbial communities (bacteria plus micromycetes) increased greatly in organic soil horizons of stands with a grassground cover and mineralization of carbon and nitrogen compounds was more intensive there than under the dead spruce trees. Decomposition and mineralization of the plant litter was also more intensive; the production of enzymes from the sulphur cycle increased in the bacterial component of microbial communities. The microflora of organic horizons increased under grass and after spruce had been replaced by birch and mountain ash.