Nitrogen-fixing blue-green algae in acid forest and nursery soils

Abstract

Algal populations were studied in soils from sites representing several major forest types ranging from the spruce–fir forests in the Appalachian Mountains to the Southern pine forests along the Atlantic Coast. In addition, the nitrogen-fixing blue-green algal population of a forest tree nursery was examined.The results of this investigation indicate a general lack of nitrogen-fixing algae in acid forest soils. However, a pronounced development of these algae was observed in the acid nursery soil, especially on the soil surface. Low numbers of algae were found in some forest soils but only when the soil was above pH 5.4. No nitrogen-fixing Cyanophyceae were isolated from soils in the Appalachian Mountains regardless of soil acidity. Nostoc muscorum was the most common nitrogen-fixing species occurring under both forest and nursery conditions. Nostoc commune was isolated only from the nursery soil. Several strains of Nostoc ellipsosporum were obtained from a mixed hardwood–softwood site. An examination of the algal flora of a number of Alaskan tundra soils gave results similar to those found in the forest soils.