Lichens as an Ecological Indicator: A Summary of a Lichen Communities Article, with Implications for Ohio

We’ll start with a summary of this article: Miller, Jesse E.D., John Villella, Daphne Stone, and Amanda Hardman. “Using lichen communities as indicators of forest stand age and conservation value.” Forest Ecology and Management 475 (2020): 118436.

Summary

Research was done in developing a continuous lichen conservation index for the Pacific NW, modeled closely after the development of Coefficients of Conservatism (CofC) used in the Floristic Quality Assessment Index (FQAI) for vascular plants. To the best of the author’s knowledge, this is the first continuous index for testing lichen affinities to forest stand age.

The intent was to explore if lichens could be effective indicators of forest conservation value and successional status.

Steps in developing the lichen conservation index were as follows:

1) Three expert regional lichenologists (each with years of lichen field experience) independently assigned values 1-10 to each epiphytic macrolichen species included in the authoritative regional lichen identification guide. As with development of vascular plant and moss CofCs, the values reflect a species’ affinity for undisturbed, late-successional or remnant habitats. Species that tend to occur in disturbed or anthropogenically modified habitats receive lower values, while species associated with late successional habitats receive higher values.

Note: macrolichens were used, as opposed to other lichen groups, since: a) they are the most commonly surveyed type of

lichens; b) they are relatively easy to ID compared to other groups of lichen taxa; c) non-experts can be trained to ID them fairly rapidly; d) distribution and ecology of these groups are much better understood than other groups.

2) Rankings between the three experts were strongly correlated, and from their values a master index based on the three sets of individual rankings was developed. (The master list is shown at the end of the journal article; a snippet is shown here.)

3) A large forest survey dataset was used to test whether the community-level lichen conservation index is related to forest stand age in a continuous fashion.

The research showed a positive linear relationship between the resulting macrolichen conservation index and forest stand age. This relationship was stronger than that between forest stand age and a simple count of lichen species or between forest stand age and a binary indicator (where species are simple flagged as old growth forest indicators or not).

It was concluded that a lichen conservation index, analogous to CofCs used for the FQAI, can be a useful indicator of stand age, as well as late successional habitats of conservation concern, and can have strong biological relevance.

Comments on implications for Ohio

• The study was based on west coast forests where there has been little in the way of reversion from agriculture to forests. (They have been mostly continuous forests since regeneration after forest cuttings.) The authors suggest additional studies with lichens in regions where there was forest regeneration from agriculture. Heterogeneous histories of forest continuity could provide more evidence about how forest continuity or lack of continuity can influence lichen communities relative to stand age.
• The above would be very pertinent to Ohio, where regeneration from agriculture has been very common. This is a large problem in Ohio and in other states in eastern North America. Agricultural lands very often have soils that suffer from many problems related to long term farming, including severe soil compaction, erosion and other related problems that provide for a lower trajectory of forest regrowth, resulting in an extended period of time in the juvenile and secondary stages of development. My thought is that both bryophyte and lichen QAIs would be valuable indicators for researching this concern.
• It seems that the logical place to start, if there was interest in developing andusing a Lichen QAI, would be to develop a set of CoCs for macrolichens of Ohio. This state has the expertise to do so and it probably could be done with a minimum of resources. Ohio, as discussed in another article, already has CofCs for bryophytes, and this expertise could be used in determining how to produce the lichen CofCs.
• By doing so, we would have the main mechanism in place for determining Lichen QAIs, whether from databases or from on the ground community monitoring.
• There could subsequently be a discussion and research to see if macrolichens could be used as an indicator for other habitats besides forests.
• The study authors just divided the sum of CofCs of species found by the number of species (producing an average CofC), whereas the FQAI divides the sum of CofCs by the square root of the number of species. This small adjustment could easily be done, thus providing a Lichen QAI. This would also provide greater distance between scores than a straight average does.

-Bill Schumacher