The importance of host tree age, size and growth rate as determinants of epiphytic lichen diversity in boreal spruce forests

Abstract

The amount of large and old trees has decreased in the boreal forests during the last centuries of forestry. Such trees are important habitats for epiphytic lichens and there is a growing concern for lichen species that are associated with large and old trees. However, only little is known about the relative importance of tree size versus age as determinants of lichen diversity. Here we have determined the size, age and growth rate of 157 Norway spruce trees and recorded the occurrence of epiphytic lichen species on their branches and lower stems. The study includes crustose lichens and was done in two old-growth forests in SE Norway. Tree age and tree size were the parameters that explained the largest part of epiphytic lichen diversity. Only the growth rate of the most recent time period, i.e. 1984-2004, showed a statistically significant relationship to diversity. There was no indication of a stabilising species number with increasing tree age. Slow-growing and old trees were, however, mainly of importance to the lichen species growing on stems, and this set of species were in general adversely affected by a large amount of branches. The opposite was the case for the species that were confined to branches as their diversity increased when the amount of branches increased. Our study adds empirical data to support the importance of large and old trees as bearers of biodiversity in boreal forests. Site preservation and patch retention of groups of old and large trees is recommended as measures to maintain epiphytic lichen diversity.

Drivers of lichen species richness at multiple spatial scales in temperate forests

“…A large body of literature supports the view that tree-level factors are fundamental for explaining lichen richness at the scale of single tree (e.g. Lie et al 2009). However, our results support the idea that at this spatial scale local factors, indicative of environmental conditions, are also influential (see also Jüriado et al 2009) and interact with tree-level factors.…”

Tree retention as a conservation measure in clear-cut forests of northern Europe: a review of ecological consequences

“…They found that retention of snags close to existing populations of red-listed species was more beneficial than an even, dispersed distribution. In another study, however, no detectable effect of hotspot landscapes with a documented rich fauna of red-listed beetles was found on the beetle fauna in high stumps (Lindbladh et al, 2007). In a follow-up study using window traps instead of bark sampling, a certain effect of hotspot surroundings could be seen for birch high stumps, but not for spruce high stumps .…”

“…The type of trees that are included in the retention groups may have a strong effect on species composition. Lie et al (2009) recommend that to maintain epiphytic flora, trees in retention groups should be large and old.…”

Evaluation of the environmental quality of a protected riparian forest in Southern Brazil

“…The diameter of the tree is correlated to space availability for lichen species development and it is known as a key factor for community structure (Belinchon et al 2007). According to Lie et al (2009) it is possible that physical-chemical bark characteristics change with time and that an old substrate can provide a different substrate in a young tree.…”