The Ecological Value of Spruce Plantations in Massachusetts

The establishment of monoculture plantations of exotic tree species is common practice for supplementing native timber stocks. Such plantations typically provide inferior habitat for wildlife compared to native forest, which may result in a net reduction in biodiversity. However, some studies report that plantations may increase net biodiversity at the landscape scale by introducing novel habitats or supplementing existing natural forests. Using point count surveys, I examined six mature Norway spruce (Picea abies) plantations in western Massachusetts in 2016 and 2017 to evaluate bird use of these habitats relative to native forest stands. Count data were analyzed using N-mixture models to correct for imperfect detection, providing more accurate estimates of true abundance. Our findings showed that overall species richness for spruce plantations was not significantly lower than that of native forest habitats. Red-breasted nuthatch (Sitta canadensis) and golden-crowned kinglet (Regulus satrapa) were most abundant in spruce plantations. Conifer dependent species such as Blackburnian warbler (Setophaga fusca) and brown creeper (Certhia americana), were significantly more abundant in spruce plantations relative to native deciduous, hemlock, and mixed stands. Species that heavily associate with broadleaf habitat were rarely observed in spruce plantations. Species that associate with eastern hemlock habitat, such as Blue-headed vireo (Vireo solitarious) and black-throated green warbler (Setophaga virens) were observed using spruce plantations at similar levels as eastern hemlock stands. These results demonstrate that Norway spruce plantations can provide suitable habitat for native species associated with conifers, which is significant given projected continued decline of eastern hemlock in response to the hemlock wooly adelgid (Adelges tsugae). Although large-scale conversion of native forest to plantations would likely lead to a loss in biodiversity, land managers could be justified in allowing small-scale plantations to persist without suffering negative impacts to native biodiversity