Landscape matrix fragmentation effect on virgin forest and managed forest birds: a multi-scale study

We executed a six-year-study of breeding bird abundances in large
forest stands in a managed boreal forest landscape. We found that the
landscape matrix fragmentation affected the structure of bird assemblages
inhabiting forest stands and that the effect was a species guild-specific. In
total, the species number was 13.4% and the pair number 16.4% lower in
forest stands surrounded by a moderately fragmented forest landscape
compared to stands surrounded by a less-fragmented forest landscape.
The decrease in pair numbers was attributed to virgin forest bird species,
whose abundance was, on average, 25.7% lower in forest stands
surrounded by a fragmented matrix. The corresponding difference among
managed forest bird species was only 7.9 %. For the abundance of virgin
forest species, the landscape matrix fragmentation was a more important
factor than the stand-level fragmentation. Instead, managed forest species seemed to benefit from the small-scale forest fragmentation within stands.
The abundance of virgin forest species was higher in stands embedded
within a less-contrasted matrix. As predicted, the matrix contrast was not
as important among managed forest generalist species. The results
suggest that virgin forest bird species suffer more from the landscape
matrix fragmentation than do managed forest bird species. In general, the
landscape context plays a significant role when determining the
occupancy and the abundance of birds within forest stands, which
supports both the matrix quality and the matrix-patch contrast
hypotheses. The new finding is that the matrix quality of a landscape may
modify bird assemblage structure even in moderately fragmented forest
landscapes, i.e. in forest landscapes which are more or less connected.