Abstract
Hair lichens are strongly influenced by forest structure at local scales, but their broad-scale distributions are less understood. We compared the occurrence and length of Alectoria sarmentosa (Ach.) Ach., Bryoria spp., and Usnea spp. in the lower canopy of > 5000 Picea abies (L.) Karst. trees within the National Forest Inventory across all productive forest in Sweden. We used logistic regression to analyse how climate, nitrogen deposition, and forest variables influence lichen occurrence. Distributions overlapped, but the distribution of Bryoria was more northern and that of Usnea was more southern, with Alectoria’s distribution being intermediate. Lichen length increased towards northern regions, indicating better conditions for biomass accumulation. Logistic regression models had the highest pseudo R2 value for Bryoria, followed by Alectoria. Temperature and nitrogen deposition had higher explanatory power than precipitation and forest variables. Multiple logistic regressions suggest that lichen genera respond differently to increases in several variables. Warming decreased the odds for Bryoria occurrence at all temperatures. Corresponding odds for Alectoria and Usnea decreased in warmer climates, but in colder climates, they increased. Nitrogen addition decreased the odds for Alectoria and Usnea occurrence under high deposition, but under low deposition, the odds increased. Our analyses suggest major shifts in the broad-scale distribution of hair lichens with changes in climate, nitrogen deposition, and forest management.
Highlights
Filamentous “hair” lichens in the genera Alectoria, Bryoria, and Usnea often dominate forest canopies throughout the boreal zone, as well as some temperate forests
Alectoria was exclusive on 1.0%, Bryoria was exclusive on 11.3% and Usnea was exclusive on 9.7%, while all genera co-occurred on 7.7% of the trees
Our models may help to interpret and predict current and future changes in regional distribution of hair lichens. Such knowledge is critical for choosing adequate measures to mitigate impacts of climate change, element deposition, and forestry on hair lichens
Summary
Filamentous “hair” lichens in the genera Alectoria, Bryoria, and Usnea often dominate forest canopies throughout the boreal zone, as well as some temperate forests. Hair lichens have important functions in forests. They participate in nutrient and water cycling, provide habitat and food for animals, and constitute a significant part of the winter diet for caribou and reindeer (subspecies of Rangifer tarandus (Linnaeus, 1758); Hauck 2011; Stanton et al 2014; Esseen and Coxson 2015). Hair lichens are useful indicators of forest ecosystem integrity and have strongly declined in areas with atmospheric pollution (Kuusinen et al 1990; Bruteig 1993) and intensive forestry (Esseen et al 1996). Hair lichens such as Alectoria sarmentosa (Ach.) Ach., Bryoria nadvornikiana (Gyeln.) Brodo & D. Hawksw., and Usnea longissima Ach. are red-listed in Fennoscandia (Kålås et al 2010; Rassi et al 2010; ArtDatabanken 2015)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
