Bird communities reveal the ecological value of non-native Norway spruce plantations in Massachusetts, USA

Abstract

The establishment of monoculture plantations of non-native tree species is a common practice for supplementing native timber stocks. Since native wildlife species may lack co-evolved traits needed to successfully exploit non-native tree species, non-native plantations are expected to provide inferior habitat for native biodiversity. However, some studies report that plantations may increase net biodiversity at the landscape scale by introducing novel habitats or supplementing existing natural forests. We used point counts to sample birds in 2016 and 2017 in mature Norway spruce (Picea abies) plantations in western Massachusetts, as well as representative native forest types, to evaluate bird use of these plantations relative to native forest types. Our findings showed that overall species richness for spruce plantations was similar to that of native forest habitats, and that several native conifer-dependent species (red-breasted nuthatch (Sitta canadensis), golden-crowned kinglet (Regulus satrapa), blackburnian warbler (Setophaga fusca), and brown creeper (Certhia americana) were significantly more abundant in spruce plantations relative to native deciduous, hemlock, and mixed stands. Bird species reported to associate with eastern hemlock (Tsuga canadensis), 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.