SAMPLING OF LUMBRICUS-TERRESTRIS (OLIGOCHAETA, LUMBRICIDAE)

The extraction of juveniles of L. terrestris was equally efficient by the application of formaldehyde or chloroacetophenone (CN) solutions and by a chloroacetophenone application followed by a handsorting to a soil depth of 110 cm. For adults the combination CN/handsorting was more efficient than the use of chemical expellants only. The efficiency of chemical expellents for the extraction of adults may have been improved through a repeated application of the chemicals on three subsequent evenings. The frequency distribution of juveniles could be described by a negative binomial, that of the adults by a Poisson distribution. These statistical distributions were used to calculate the sample size for a given reliability. It is concluded that if adult and juvenile L. terrestris are abundant, their population densities are reliably estimated in a homogeneous environment by taking 10 sample units of 50 cm x 50 cm per sample. However, in non-homogeneous environments or in habitats with low earthworm population density, the appropriate sample size is expected to be much higher. Therefore, further investigations should not only concentrate on the elevation of the control of the extraction efficiency, but also should aim to reduce the time needed for the sampling.