Changes in bacterial populations in a clear-cut beech forest soil planted with spruce

Abstract

A beech forest after clear-cutting was replanted with spruce. To study how this perturbation affected soil bacteria and their physiological capabilities, an investigation was undertaken 4 years after the change of forest type. Compared with an earlier study in the beech forest, from 1972 to 1975, conducted immediately before clear-cutting, bacterial numbers in the young spruce plantation had increased; an exception was the upper layer (A00), where the numbers decreased. The population densities of bacteria decomposing xylan, pectin, starch, cellulose, and chitin were estimated by a direct multipoint method. The numbers of bacteria in all the physiological groups studied were higher in 1979–1980, with the same exception as before (A00). The greatest changes occurred in the upper horizons. There were considerable changes in the soil environment after the former beech litter fall ceased; the forest floor became more exposed, and the ground vegetation changed. Changes took place in soil properties, such as organic matter and pH. A slight increase in pH was observed in all horizons except in A00, and organic matter increased in two of the horizons (A01/A1; A1).