Consequences for bird diversity from a decrease in a foundation species—replacing Scots pine stands with Norway spruce in southern Sweden

Abstract

Forest ecosystems are often defined by their dominant foundation tree species, which dictate forest structure and ecosystem processes. In southern Sweden, concerns are being raised because production stands of a foundation tree species, Scots pine (Pinus sylvestris), are being converted to Norway spruce (Picea abies) stands. Such conversions may lead to biodiversity loss, though the specific nature and extent of such losses remain unknown. Here, we assess the potential biodiversity impacts by contrasting the bird communities of 55-and 80-year-old Scots pine and Norway spruce production stands. We also determine the extent to which these production stands capture the available species pool by surveying conifer-dominated reserves. Our results indicate that Scots pine and Norway spruce production forests support overlapping but nevertheless distinct bird communities, though only few recordings were made of the species unique to either stand type. Among the production stands, the 80-year spruce stands had the highest average bird species richness, and largest total number of species recorded. We suggest that the higher diversity can be explained by a higher proportion of broadleaves and higher volumes of dead wood. Although the bird diversity found in the reserves was lower than expected, they benefit gamma diversity at landscape scales as they collectively supported a higher diversity of bird species than the production forests. In summary, the conversion of Scots pine to Norway spruce is likely to increase the homogeneity of the bird communities in this region.

The tree species matters: Biodiversity and ecosystem service implications of replacing Scots pine production stands with Norway spruce

“…Goldcrest (Regulus regulus) may also contribute to differences in community composition, as this species is often associated with spruce (Haapanen 1965). Targeted surveys of 55 and 80-year-old spruce and pine production stands in southern Sweden found that bird community composition differed in line with these expectations, but that older spruce stands can support higher bird diversity than pine, with effects depending on rotation length and broadleaf retention practices (Lindbladh et al 2019).…”

How generalist are these forest specialists? What Sweden’s avian indicators indicate

“…2). This may reflect the fact that several of the reserves included in this study lacked some old‐growth forest characteristics (see Lindbladh et al ., 2019). However, the outcome may also reflect the difficulties involved in finding bird species indicative of high natural values in this region.…”

“…We used survey data from three published (Lindbladh et al, 2014b(Lindbladh et al, , 2017(Lindbladh et al, , 2019 and one unpublished study (A. Felton, P.-O. Hedwall, E. Holmstr€ om, R. Trubins, J. Lagerstedt, & M. Lindbladh, in prep).…”

“…The 101 stands included in the study were distributed in the forest-dominated counties of Halland, Kronoberg, Kalmar, J€ onk€ oping and V€ astra G€ otaland ( Table 2). The 91 production stands used were chosen due to survey requirements, see previous publications for more information (Lindbladh et al, 2014b(Lindbladh et al, , 2017(Lindbladh et al, , 2019. For most part they were typical of conifer-dominated planted production forests in the hemi-boreal vegetation zone of Sweden.…”

“…For more information on the bird survey methodology see Lindbladh et al (2019) Stand level structures A similar methodology for surveying stand level forest structures was used across all studies. Ten plots in each stand were surveyed for living trees, living shrubs and dead wood (Table 3).…”