Reduced Diversity and Relative Abundance of Terrestrial Snails in a Red Pine Plantation Compared with a Surrounding Northern Red Oak – Large-toothed Aspen Woods

Résumé

A Red Pine (Pinus resinosa Aiton) plantation and adjacent Northern Red Oak (Quercus rubra L.) – Large-toothed Aspen (Populus grandidentata Michx.) woods, both of which developed from a savannah scrub beginning approximately 60 years ago, were compared with regard to terrestrial snail diversity and abundance. The comparison involved a 30-minute search of ten 1-m2 quadrats at ten sites in each habitat. In the Northern Red Oak – Large-toothed Aspen woodland, 13 species and 661 individuals were recorded, whereas, in the Red Pine plantation, six species and 24 individuals were recorded. In the Northern Red Oak – Large-toothed Aspen woodland, the most characteristic and abundant species was Novisuccinea ovalis (Say, 1817), which was present in 74 of the 100 quadrats and was represented by 460 individuals. In the pine plantation, the most common species was Zonitoides arboreus (Say, 1816), which was present in 16 quadrats and was represented by 17 individuals. This species was the second most common in the Northern Red Oak – Large-toothed Aspen woodland where 70 individuals were found in 34 quadrats. In both habitats, Z. arboreus was associated with downed wood. Other species occurring in more than 15% of quadrats in the Northern Red Oak –Large-toothed Aspen woodland were Strobilops labyrinthicus (Say, 1817), Glyphyalinia indentata (Say, 1823), and Euche motrema fraternum (Say, 1824). Although a lower number and diversity of terrestrial snails in the conifer plantation was expected, the contrast was greater than anticipated. The estimated abundance of 46 000 N. ovalis per hectare suggests the potential importance of these medium-sized snails in the relatively dry Northern Red Oak – Large-toothed Aspen ecosystem.