Seasonal fluctuations in numbers of aerobic bacteria and their spores in four horizons of a beech forest soil

Abstract

This paper reports a 3-yr study of the numbers of bacteria and spores in a beech forest soil, their patterns of distribution, abundance, and fluctuations, and discusses the factors responsible for the fluctuations. There was an abundant bacterial population in the acid brown forest soil, despite its low pH. There were significant differences in the numbers of bacteria between soil horizons, but differences in the numbers of bacterial spores were less pronounced. The numbers of bacteria in the surface horizons fluctuated, with peaks occurring twice a year: the higher peaks occurred after leaf-fall in autumn, and the smaller peaks occurred in spring at the time of leaf-burst and rapid development of understory vegetation. After a severe attack on the beech trees by larvae of Dasychira pudibunda L. in the summer of 1973, the peaks in autumn did not reach the same levels as in other years, indicating the importance of perturbations in leaf-fall to fluctuations in bacterial numbers.