Density and biomass of earthworms in forest and herbaceous microecosystems in central New York, North America

We have determined and assessed the earthworm population community structure under different selected microecosystems (i.e. forest ecosystem and herbaceous ecosystem). Samples of earthworms and soil were studied from four sites in Lafayette Forest Experimental Station, State University of New York, College of Environmental Science and Forestry. These sites are the Northern Hardwood forest, Tamarack plantation, Norway spruce and Old Field Herbaceous. They represent temperate woody (forest) vegetation cover and herbaceous ecosystems. Samples were collected from summer 1984 through early summer of 1985. The comparative study of temperate earthworm populations under these sites showed that the optimal physico-chemical soil environment for earthworms includes a 20–35% soil water content, a soil pH of 5.8–6.2 and soil Eh of 510–640 mV. Application of diversity and similarity indices showed that diversity of earthworm populations increases with increased species numbers. At the same time, there is a negative correlation between diversity and population density (ind./species) in CSD (Community Structure Diversity) scale that explains the sensitivity of CSD index toward the rare species. Similarity indices showed that earthworm populations of similar vegetative cover are very similar. Earthworm communities exhibit the lowest similarity between the coldest and hottest seasons in all habitats studied. Also, there is a similarity between consecutive seasons in the different habitats. It was found also that spring and summer seasons are the most important seasons for the increase in Aporrectodea earthworm species in central New York. Aporrectodea tuberculata and Octalasion tyrtaeum are the numerically dominant species, while the dominant genus of juvenile earthworms is Lumbricus spp. (J) based upon the ISA index (Roberts and Hsi, 1979). There was a significant association between anecique and epigeic species and between epigeic and endogetic species. This shows that earthworms depend on the type of dominant vegetative cover in the site. Finally, the litter composition is the factor that affects earthworm abundance and biomass on the sites.