POPULATION-DYNAMICS OF LUMBRICUS-TERRESTRIS L (OLIGOCHAETA, LUMBRICIDAE) IN A MEADOW

The population dynamics of the earthworm L. terrestris L. was studied from April 1987 to September 1988 in a meadow which was frequently mowed. After mowing, the cut plant material was left on the plot as food for the earthworms, except for small samples which were removed to estimate the dry weight of the cutting per unit area. In both years rainfall was regularly distributed and the soil was never dry in lower layers. Soil water was assumed to be a non-limiting factor for L. terrestris in this experiment. The demand for food of L. terrestris was calculated using a nonlinear function of soil temperature cited in the literature. It was demonstrated that at the prevailing temperatures the earthworms' demand for food could not be satisfied by the available cut plant material. The biomass, growth and development of L. terrestris was followed during the two seasons. Fluctuations in population density are mainly due to the juveniles. Adults had a rather constant abundance during the 2 yr of investigation. Juveniles hatched in late spring and in autumn. L. terrestris in the field grew slower than in the laboratory, matured later, reached higher body weight at the onset of maturity but lower maximum adult weight. It is concluded that individuals of L. terrestris had to face intense intraspecific competition for food resources in the meadow. Bawd on the observed population dynamics and recent investigations in the laboratory on fife cycle traits, it was confirmed that L. terrestris is more ''K''-selected than other members of the Lumbricidae.