DENSITY AND DISTRIBUTION OF DENDROBAENA-OCTAEDRA (LUMBRICIDAE) IN ASPEN AND PINE FORESTS IN THE CANADIAN ROCKY-MOUNTAINS (ALBERTA)

Dendrobaena octaedra (Savigny) and to a lesser extent Dendrodrilus rub idus (Savigny) recently colonized an aspen (Populus tremuloides Michx. ) and pine (Pinus contorta Loud.) forest in the Rocky Mountains of sou thwest Alberta (Canada). Soil sampling along transects from a road int o aspen and pine forests in 1992 showed that earthworm numbers decreas ed with distance from the road in both forests. A maximum of 3218 and 627 ind. m(-2) were found in the aspen (August) and Dine forest (June) , respectively. Earthworm density in the aspen forest increased from M ay until August reaching a maximum of 2621 ind. m and then decreased. Juveniles dominated and only a few adult specimens were present. Cocoo n density varied between 2536 and 3699 m(-2). Within the soil profile cocoons were almost exclusively located in H material. The vertical di stribution of D. octaedra varied between sampling dates. From May to J uly earthworms preferentially colonized H material whereas in August a nd September most earthworms were found in F material. The data indica te that only few earthworms survive the harsh winter conditions. The r ate of survival of cocoons was relatively high (average 48%), but viab ility depended on cocoon size. (C) 1997 Elsevier Science Ltd.