Bark beetle infestation alters mycobiomes in wood, litter and soil associated with Norway spruce.

Abstract

Recent exceptionally hot and dry summers provoked massive bark beetle outbreaks in German forests, which killed many conifers, forcing to clear-cut complete non-mature stands. The importance of fungi in ecosystems in particular in association with trees is widely recognized, but the ecology of how insect infestations of trees affects their mycobiomes remains poorly understood. Using Illumina MiSeq sequencing, we investigated fungal communities in soil, litter and stem-wood at early and late stages of bark beetle infestation in a Norway spruce (Picea abies (L.) Karst) stand in Central Germany. Fungal diversity decreased from soil to wood, with the highest proportion of unknown fungi in stem-wood. Lifestyles, particularly of those fungi associated with stem-wood, clearly changed depending on the infestation stage. The answer of tree associated fungi to beetle infestation was characterized by an increasing community dissimilarity among all three habitats, i.e. it concerned not only the above ground fungal communities directly connected to the tree. Our study, thus, pin points the cascading effects of tree infestations by bark beetles and subsequent tree dieback on the proximate and distant mycobiomes of the plant soil system, which should be entirely considered to tackle the effects of environmental events on tree health.