Data from: Small beetle, large-scale drivers: how regional and landscape factors affect outbreaks of the European spruce bark beetle

Unprecedented bark beetle outbreaks have been observed for a variety of
forest ecosystems recently, and damage is expected to further intensify as
a consequence of climate change. In Central Europe, the response of
ecosystem management to increasing infestation risk has hitherto focused
largely on the stand level, while the contingency of outbreak dynamics on
large-scale drivers remains poorly understood. To investigate how factors
beyond the local scale contribute to the infestation risk from Ips
typographus (Col., Scol.), we analysed drivers across seven orders of
magnitude in scale (from 103 to 1010 m²) over a 23-year period, focusing
on the Bavarian Forest National Park. Time-discrete hazard modelling was
used to account for local factors and temporal dependencies. Subsequently,
beta regression was applied to determine the influence of regional and
landscape factors, the latter characterized by means of graph theory. We
found that in addition to stand variables, large-scale drivers also
strongly influenced bark beetle infestation risk. Outbreak waves were
closely related to landscape-scale connectedness of both host and beetle
populations as well as to regional bark beetle infestation levels.
Furthermore, regional summer drought was identified as an important
trigger for infestation pulses. Large-scale synchrony and connectivity are
thus key drivers of the recently observed bark beetle outbreak in the
area. Synthesis and applications. Our multiscale analysis provides
evidence that the risk for biotic disturbances is highly dependent on
drivers beyond the control of traditional stand-scale management. This
finding highlights the importance of fostering the ability to cope with
and recover from disturbance. It furthermore suggests that a stronger
consideration of landscape and regional processes is needed to address
changing disturbance regimes in ecosystem management.