Earthworm densities in central Amazonian primary and secondary forests anda polyculture forestry plantation

The species composition, abundance and biomass of earthworms were determine d in two plots of a polyculture forestry plantation (POA, POC) and in plots of nearby secondary (SEC) and primary (FLO) forest since 1997. In contrast to recommendations in the literature, hand-sorting was not successful for collecting the worms due to their individual size (2 cm to 110 cm in length ) and their inhomogeneous distribution. In a preliminary study it was confi ned that formalin extraction in areas of 4 m2 is an easy and quick method t o sample earthworms qualitatively and quantitatively. After eight sampling dates in the period from July 1997 to March 1999 the f ollowing results can be presented: The number of species is not very high (approximately 8; mainly Glossoscole cidae). One peregrine species (Pontoscolex corethrurus) was found in the po lyculture plot and one other (Dichogaster bolaui, Octochaetidae) nearby. The abundance of earthworms in the FLO plot is low in comparison to many ot her tropical rain forest sites ton average 3.0 +/- 2.4 ind/m(2) compared to 68 +/- 32 ind/m(2)). On the other hand, the amount of biomass is within th e normal range known from other rain forests ton average 15.3 +/- 10.4 g fr esh weight m(-2) in comparison to 12.9 +/- 6.2 g fresh weight m-L?). Number and biomass of earthworms on the other three plots are considerably lower than on the FLO plot and also lower than reported from the literature (based on very few studies).