Do epiphytic lichens negatively impact their hosts through allelopathy? The effect of Evernia esorediosa on growth and biochemical processes of Larix gmelinii.

This article investigates the allelopathic interaction between the epiphytic lichen Evernia esorediosa and its host tree Larix gmelinii in Siberian cryolithozone boreal forests. The study demonstrates that usnic acid (UA), a secondary metabolite produced by E. esorediosa, migrates from the lichen thalli into the bark, phloem, roots, and needles of L. gmelinii, disrupting key cellular processes such as photosynthesis, respiration, and oxidative phosphorylation. This biochemical interference correlates with significantly reduced radial and apical growth in larch trees heavily colonized by the lichen, suggesting that E. esorediosa exerts an allelopathic effect that may ultimately impair tree vitality. The findings contribute to understanding the complex biochemical interactions between epiphytic lichens and their host trees in boreal ecosystems.