Data from: Characterizing combined fire and insect outbreak disturbance regimes in British Columbia, Canada

Context: Fires and insect outbreaks are important agents of forest
landscape change, but the classification and distribution of these
combined processes remain unstudied aspects of forest disturbance regimes.
Objectives: We sought to map areas of land characterized by homogenous
fire regime (HFR) attributes and by distinctive combinations of fire, bark
beetles and defoliating insect outbreaks, and how their distribution might
change should current climatic trends continue. Methods: We used a 41-year
history of mapped fires and forest insect outbreaks to classify HFRs and
combined fire and insect disturbance regimes (HDRs). Spatially constrained
cluster analysis of 2524 20-km grid cells used mean annual area burned,
ignition Julian date, fire size and fire frequency to delineate HFR zones.
Mean annual areas burned, affected by bark beetles, and affected by
defoliators were used to delineate HDR zones. Random forests
classification used climate associations of HDRs to project likely changes
in their distribution. Results: Eighteen HFR zones accounted for 30% of
variance, compared to 27 HDR zones accounting for 59% of variance. Fire
regime designation had low predictive power in explaining 23 homogenous
insect outbreak regimes or the 27 HDRs. Climate change projections
indicate a northward migration of current HDR zones. Conditions suitable
for defoliator outbreaks are projected to increase, resulting in a
projected increase in the total rate of forest disturbance. Conclusions:
When describing forest disturbance regimes, it is important to consider
the combined and possibly interacting agents of tree mortality, which can
result in emergent properties not predictable from any single agent.