Short-rotation bioenergy stands as an alternative to spruce plantations: implications for bird biodiversity

Abstract

• There is a gap in knowledge regarding the biodiversity implications of replacing production forests with bioenergy stands.• We compared the avian biodiversity of early rotation hybrid aspen stands and spruce plantations, the latter being the dominant production forest type in southern Sweden.• Our results indicate that young hybrid aspen stands can support relatively diverse and distinctive bird communities. AbstractGlobal efforts to decrease dependence on fossil fuels have increased interest in bioenergy production. One source of bioenergy is fast growing deciduous tree species, such as hybrid aspen (Populus × wettsteinii Hämet-Ahti). The majority of research on hybrid aspen which assesses biodiversity implications, has however primarily focused on agricultural lands as the reference condition. This has resulted in a substantial gap in our knowledge regarding the biodiversity implications of replacing production forest types with hybrid aspen, a form of reforestation taking place in northern Europe. In this study we address this knowledge gap by comparing the avian biodiversity of young hybrid aspen and spruce (Picea abies L.) plantations of similar age, the latter being the most prevalent forestry alternative in in southern Sweden. We found that hybrid aspen stands had higher bird species richness and abundance as well as a distinct community composition compared to the spruce stands. We suggest that the most likely driver was the greater structural and tree species complexity in the aspen stands, provided for by the fenced exclusion of ungulates from the regenerating hybrid aspen stands. Our results indicate that at least during early stages of regeneration, and in comparison to the dominating production forest type in the region, hybrid aspen stands can support relatively high levels of bird diversity, and a bird species composition more closely associated with broadleaf habitat types requiring restoration in this region.

Broadleaf Retention Benefits to Bird Diversity in Mid-Rotation Conifer Production Stands

“…In contrast, birds that are associated with open land, and often found on recent clear-cuts, e.g. common whitethroat (Sylvia communis) and yellowhammer (Emberiza citrinella) (Söderström, 2009;Lindbladh et al, 2014b), were absent in the mid-aged production stands in our study, indicating a change in bird composition since the clear-cut phase. However, ground-nesting birds not associated with clear-cuts were frequently encountered (Table 1), and were significantly more common in the GTR stands than in the controls (Fig.…”

Bird Species

“…Also, climate change mitigation measures have the potential to reduce the impact of climatic change by up to 20% for birds (Warren et al 2013) and in some cases are already promising regarding positive impacts on bird communities (Lindbladh et al 2014). However, several mitigation measures show adverse effects on bird populations and diversity (Danielsen et al 2009;Immerzeel et al 2014).…”

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

“…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.…”

“…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).…”