Business as usual: macrolichen community response to the resilience of spruce–fir forests to beetle disturbance in northwestern Colorado

Abstract

Over the past few decades, spruce beetles (Dendroctonus rufipennis Kirby) have drastically altered spruce–fir forests in western North America. Past research has shown that forest conditions (i.e., canopy openings, amounts of coarse woody material) change after spruce beetle disturbance, but little work has studied the impacts of these changes on the resident biotic communities. Even less research has investigated how spruce beetle disturbance affects lichen communities, which we anticipated as benefiting them due to canopy opening and increased woody material availability. We studied macrolichen community structure, including abundance and community composition, and habitat characteristics in areas with significant spruce beetle damage, as first detected between 1996 and 2017 in northwestern Colorado. We found few habitat differences among beetle disturbance classes that reflected varying time since infestation, and only the most recently affected plots (2012–2017) had significantly different lichen community structure relative to other sampled areas. We observed that the spruce–fir forests within our study exhibited ecological resilience to beetle outbreaks, and we did not measure differences in the amount of canopy openings or amounts of coarse woody material. Subsequently, the lack of differential lichen community response was not surprising.