Plant Composition in Relation to Vole Damage in Coniferous Plantations

We analysed the plant composition of several coniferous plantations of Eastern Townships of Quebec to examine the relationships between biomass patterns and levels of damage made by meadow voles (Microtus pennsylvanicus) to young trees. The biomass of the most abundant grass species was compared in severely damaged, lightly damaged and undamaged plantations. Damage indices per plantation were standardized using the composite Mizushima (1976) index. Total biomass did not differ between the three categories of plantations analysed. However, heavily damaged plantations contained significantly more biomass of Virginia strawberry (Fragaria virginiana) and less of couch-grass (Agropyron repens). Debarking damage by voles was not concentrated on specific coniferous species but occurred rather in meadows where Fragaria was relatively more abundant. To reduce tree loss due to vole debarking, we recommend an initial survey of the biomass be made at future planting sites and seedlings be planted in meadows with low biomass. Sites with low biomass of Fragaria and high biomass of Agropyron would probably be the best ones. Key words: Plantations, conifers, damage, debarking, voles, biomass, Microtus pennsylvanicus, Fragaria virginiana, Agropyron repens, Quebec.