Type of Resources
Spruce beetle disturbance has affected millions of acres of forest throughout North America and Europe, but thus far little research has investigated how this disturbance influences lichen communities. To address this problem, we studied lichen communities and habitat characteristics within 44 plots across a chronosequence of spruce beetle damage spanning 1996–2017 in northwestern Colorado. We found 82 species of lichens, few habitat differences among spruce beetle disturbance classes, and only the most recently affected plots (2012–2017) had significantly different lichen community structure relative to remaining areas. Two primary gradients explained the majority of variation of lichen community structure within our study area. The first gradient was related to forest location and substrate, with the positive end of the axis associated with the Routt NF, higher partially decayed wood, and more bare ground, while the negative end of axis one was associated with plots located in the Roosevelt NF which had higher lichen species richness, more heavily-decayed wood, and more lichen and plant understory cover. The second gradient described lichen community trends related to canopy closure on the positive end of the axis while higher wind speeds and heavily decayed logs were associated with the negative end of this gradient. We suggest that differences in habitat characteristics that we noted as related to spruce beetle disturbance, were instead due to our sampling method and large plot size. Further we speculate that recovery of understory plants and subalpine fir may compensate for the loss of spruce, manifesting as minimal differences in forest structure and lichen community structure across beetle disturbance classes. Slow recovery times of lichens could have also inhibited our ability to detect a response to spruce beetle disturbance. Future researchers should further examine the response of lichens to spruce beetle response since this disturbance type will continue to affect native forests and associated organisms into the foreseeable future.
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