Continuous cover forestry favour hair lichens

The study was carried out in Vindeln Experimental Forests. The photo shows strongly thinned forest (67 percent removal) with datalogger that measures temperature, relative humidity and light.

ImagePer-Anders Esseen

“Hair lichens have important functions in coniferous forest ecosystems and provide forage, habitat and nest material for mammals, birds, insects, and spiders. These lichens are particularly important for reindeer husbandry and can be decisive for the survival of reindeer in winter when ground lichens are unavailable. Knowledge of how environmental factors regulate abundance of hair lichens is important to develop forest management methods that can maintain hair lichens, and to understand how lichens are affected by climate change” says Per-Anders Esseen, professor emeritus at the Department of Ecology, Environment and Geoscience at Umeå University.

Strong thinning decreased hair lichens

“The lichen mass in a forest depends on the balance between colonization, growth and losses, and is regulated by the amount of available substrate, microclimate, the lichen’s colour and dispersal capacity” says Per-Anders Esseen.

Per-Anders Esseen measures the mass of hair lichens in a sample tree of spruce.

ImagePer-Anders Esseen

The lichen mass per tree decreased shortly after logging but thereafter decreased up to four times in partial cuts, with largest increase in the lower part of the trees. The stand-level lichen mass increased after moderate thinning, but decreased after strong thinning, due to fewer host trees and loss of lichens by strong wind.

Horsehair lichen (Bryoria) with dark cortical pigments.

ImagePer-Anders Esseen

“Increased light is the most important factor promoting hair lichen accumulation after partial cutting” says Per-Anders Esseen.

Dark hair lichens increased faster

Lichens are complex partnerships between fungi and photobionts (an alga, or a cyanobacterium), which passively take up water. The researchers found that dark hair lichens with melanin pigments increased faster with increased thinning level than pale lichens. The algae in dark lichens receive less light than algae in pale lichens. Dark lichens have lower photosynthesis in dense forests than pale lichens but have higher photosynthesis and growth in thinned forest with high availability of light.

“Our results show that continuous cover forestry can significantly increase the amount of hair lichens in managed forests, which is particularly important in important winter grazing areas for reindeer” says Per-Anders Esseen.