Nitrogen-Fixing Blue-Green Algae in Swedish Soils

Abstract

The importance of nitrogen-fixing bluegreen algae in the nitrogen economy of different ecosystems as rice fields (Singh 1961), deserts (Fuller et al. 1960) and various sea shore regions (Stewart 1965) has been studied. However, information about the nitrogenfixing capacity of these algae in ordinary soils is scarce and Stokes (1940) and later Beck (1968), among others, have suggested that the quantitative importance of blue-green algae as nitrogen-fixers in temperate soils is probably small. On the other hand considerable amounts of nitrogen have been shown to be fixed by these algae in ordinary soil under special conditions (Henriksson 1961). How great is their part in the nitrogen turnover in temperate soils? To help answer this question an investigation has been made on the distribution of potential nitrogen-fixing blue-green algae in Swedish soils. This study was part of the International Biological Programme. Our aim has been to find out in which soil types nitrogen-fixing blue-green algae occur in such a quantity that they might be important for the nitrogen economy of the soils. These studies, which concern the abundance of nitrogen-fixing blue-green algae, will be followed by a survey of the nitrogen-fixing capacity in situ and in monocultures using