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COSEWIC assessment and status report on the Boreal Felt Lichen in Canada

Habitat

Habitat Requirements

General Overview

Generally, most habitats of Erioderma pedicellatum are found on northerly exposed slopes where cool and moist habitat conditions prevail, throughout much of the year. Under exceptional circumstances in Newfoundland, E. pedicellatum habitats are also found on or near the East-West running forested ridges of special geological formations (Ahti, 1983; Delaney and Cahill, 1977). Here too, there is acontinuous supply of moisture provided by the flow of cool air across the ridges, rising from adjacent valley wetlands to the South or Southwest. Such situations have been encountered, e.g., in the headlands of Hermitage Bay, on Ripple Pond Ridge and in Lockyer’s Waters. Because of the predominance of cyanophilic lichens, such as E. pedicellatum, in this wet variant of the Boreal Forest, the authors have named this unique habitat: The "Suboceanic Lichen Forest of Atlantic Canada".

In these suboceanic forest types, Erioderma pedicellatum is most commonly found on the trunks of balsam fir. In Newfoundland it also occurs on black spruce, although to a much lesser extent. Because the early stages in thallus development is photophilous (“light-loving”), the lichen is most often found on these trees at or near the bottom of slopes, where the habitat is open and, as well, adjacent to Sphagnum-rich wetlands. Sphagnum species are important in maintaining moisture levels in these forest habitats during periods of drought.

Erioderma pedicellatum is, in phytosociological terms, a species of the “Lobarion” a lichen association that contains, amongst many other epiphytic lichens, several species of Lobaria, most importantly L. scrobiculata. Since L. scrobiculata can be spotted from a distance, on account of its size and colour (brownish yellow in the dry state and bluish green in the wet state), it was a useful guide in the surveys conducted to study the distribution of E. pedicellatum in the boreal forests of Nova Scotia as well as those of Newfoundland (Maass 1983). It continues to be a good indicator for suitable microhabitats for E. pedicellatum on balsam fir. Other members of the Lobarion include Lobaria pulmonaria, L. quercizans and Pseudocyphellaria crocata, all of which commonly occur on a wide range of deciduous trees and shrubs and even on conifers. Whereas these species may often be found in abundance on spruces (along with Lobaria scrobiculata) in nutrient-rich forested slopes and flood-plain habitats, they are only exceptionally present on balsam fir, which is the principal phorophyte for Erioderma pedicellatum.

The mature forest habitat in which Erioderma pedicellatum is found is characterized by distinct herbaceous flowering plants and cryptogam species. The herb layer is characterized by the presence of such species as: Clintonia borealis, Coptis trifolia, Cornus canadensis, Gaultheria hispidula and most importantly by the moisture dependent Osmunda cinnamomea. In half-open alluvial woods the latter may be replaced by Onoclea sensibilis. Sphagnum mosses include S. girgensohnii,S. fallax, S. nemoreum and/or S. russowii. Other bryophytes that predominate include the hepatic Bazzania trilobata, the pleurocarpous mosses Hylocomium splendens, Pleurozium schreberi, Ptilidium crista-castrensis and Rhytidiadelphus triquetrus and the acrocarpous mosses Dicranum majus and D. scoparium. The crowns of the trees are typically covered by a very lush growth of beard lichens, including Usnea longissima, Alectoria sarmentosa and Bryoria trichodes ssp. trichodes. The presence of these beard lichens in the canopy of the forest can act as a moisture buffer to maintain high humidity conditions.

It is assumed that the limit of distribution for Erioderma pedicellatum is reached where the climatic conditions are not sufficiently cool and humid to maintain a constant supply of moisture during the warmer and drier parts of the year. The northernmost locality where E. pedicellatum had been sighted on black spruce (Picea mariana) is in the northernmost section of the Burgeo Road (just below lat. 48º30'N; see Figure 6). The northernmost limit of the known distribution of E. pedicellatum is reached on the western side of the Northern Peninsula of Newfoundland just north of Hawkes Bay (lat. 50º43') (Figure 3).

Regardless of the distributional limits of this species, certain generalized statements can be made regarding its ecological requirements. In well-lit forests, E. pedicellatum is found mostly on trunks, in contrast to shaded habitats where the species is found predominately on branches. An important ecological balance may explain the preference of trunks or branches namely in those niches where the requirements for light are being balanced against those for uninterrupted conditions of high humidity. It is possible that in Nova Scotia the humidity levels in suitable woodland habitats for Erioderma have been too discontinuous during the warmest parts of the year to allow the branches to be colonized, even those on Abies. Only two exceptional thalli had been encountered on branches within the lowlands of Richmond County in southeastern Cape Breton Island (localities NS-42 and NS-43).

Symbiosis with Frullania

The hepatic Frullania tamarisci ssp. asagrayana plays a central role in helping Erioderma pedicellatum become established on the trunks of suitable conifers (Maass, 1986). Frullania species are distinguished by the possession of more or less helmet-shaped involutions on the underside of the dorsal leaves. These water sacs are important for a prolonged supply of moisture, and contain growth inhibitors, bacteriostatic compounds and insect-feeding deterrents (Burnett et al., 1974; Asakawa et al., 1976). Within these aseptic watersacs it is believed the process of lichenization begins in such a way that the E. pedicellatum fungus genetically recognizes the free-living Scytonema. Subsequent to lichenization, Frullania provides suitable nursery beds for the establishment and growth of the juvenile stages of E. pedicellatum, which would otherwise be difficult on the naked barks of phorophytes. In exceptional cases in which Erioderma pedicellatum has been found on red maple, this function may be performed also by Frullania bolanderi or F. oakesiana

Conversely, Frullania may benefit from the products of nitrogen fixation supplied by the newly formed thalli of cyanophilic lichens and by the still free-living cyanobiont cells within the watersacs. Frullania may even benefit from certain metabolites of the lichen fungi being released, such as growth hormones (IAA, gibberellic acids). Even the secretion of some polyketide-derived aromatic lichen acids might be of some use to Frullania.

Dr. Tomas Hallingbäck observed, in the forests of southern Sweden some years ago, that leafy hepatics like Frullania, Porella, Ptilidium pulcherrimum and Radula are good micro-environmental substrates for cyanobacteria (unpublished data). He also placed emphasis on his findings that some epiphytic mosses can likewise serve as a good microenvironment for cyanobacteria. Leucodon sciuroides was quoted as having the highest concentration of Nostoc species (pers. com.). Leucodon brachypus var. andrewsianus has been reported as Leucodon sciuroides in Erioderma habitats in Newfoundland (Crum and Anderson, 1981).

Brief Note on Bark Acidities

The acidities (Figures 9-11) and buffering capacities of the barks of the lichen phorophytes play a key role in accommodating or rejecting nitrogen-fixing lichen epiphytes on account of their high sensitivity to air pollution. The effect of bark acidity on the colonization of Lobarion lichens had been observed in the wet forest habitat of the Musquodoboit River Valley adjacent to the Limestone Quarries at Upper Musquodoboit (Maass 1983). Here, in an inland area where Lobaria scrobiculata does not normally occur on this substrate, the fir trunks had become literally covered by this lichen due to the neutralizing effects of limestone on the bark. However, more astonishing was the fact that black spruce trees in the same habitat had not been colonized at all, in spite of the neutralizing effects of the limestone. Higher bark pH (Figure 11), together with the greater water retention capacity of balsam fir bark (Figure 12), could explain why this species is the preferred phorophyte for Erioderma pedicellatum, both in Nova Scotia and in Newfoundland. This same phenomenon on spruce was also observed in Oslo, Norway, in the Ostmarka Forest Reserve (Gauslaa, 1995; Holien, 1982).

Numerous samples of Frullania were collected from Upper Musquodoboit, on both black spruce and balsam fir for sectioning and microscopic examination of the contents of their water sacs. No evidence was found for the presence of cyanobacteria in the Frullania samples from spruce, whereas more often than not the healthy random samples of Frullania from firs contained cyanobacterial cells.


Protection/Ownership

The boundaries of Jipujijkuei Kuespem Provincial Park were amended in 1997 to allocate a 213 ha portion to the Conne River Mi’gmaw Band to operate a private campground. Development is possible in this area; however, any proposal has to go through the provincial regulatory review process. The remaining 669 ha are still under the jurisdiction of the provincial government and protected under the Provincial Park Act. Much of the Erioderma population occurs within the new park boundaries.


Figure 9: pH Values Recorded for the Outer and Sub-surface Barks which had been Sampled from Trunks of Picea mariana During 1983 and 1984 in Nova Scotia and Processed as well as Measured Under Standardized Conditions

Figure 9: pH Values recorded for the outer and sub-surface barks which had been sampled from trunks of Picea mariana during 1983 and 1984 in Nova Scotia and processed as well as measured under standardized conditions.

The scale of pH values has been plotted on the x axis, whereas the numbers of equivalent measurements obtained above the baseline are being shown on their respective coordinates parallel to the y axis.

Note that the actual numbers of measurements correspond to n+1 (as far as measurements have been plotted on the baseline).


Figure 10: pH Values Recorded for the Outer and Sub-surface Barks which had been Sampled from the Trunks of Picea glauca During 1983 and 1984 in Nova Scotia and Processed as well as Measured Under Standardized Conditions

Figure 10: pH Values recorded for the outer and sub-surface barks which had been sampled from the trunks of Picea glauca during 1983 and 1984 in Nova Scotia and processed as well as measured under standardized conditions.

The frequencies for the occcurrence of Coccocarpia palmicola (x) and Lobaria scrobiculata (o) on the tree barks sampled have been indicated by the symbols shown in brackets.

Note that the actual numbers of measurements correspond to n+1 (as far as measurements have been plotted on the base line).


Figure 11: pH Values Recorded for the Outer and Sub-surface Barks which had been Sampled from the Trunks of Abies balsamea During 1983 and 1984 in Nova Scotia and Processed as well as Measured Under Standardized Conditions

Figure 11: pH Values recorded for the outer and sub-surface barks which had been sampled from the trunks of Abies balsamea during 1983 and 1984 in Nova Scotia and processed as well as measured under standardized conditions.

The frequencies for the occurrence of Coccocarpia palmicola (x) and Lobaria scrobiculata (o) on the tree barks sampled have been indicated by the symbols shown in brackets.

Note that the actual numbers of measurements correspond to n+1 (as far as measurements have been plotted on the baseline).


Figure 12: The Water Retention Capacities for the Freshly Collected and Water Saturated Trunk Barks of Abies balsamea and Picea mariana Respectively

Figure 12: The water retention capacities for the freshly collected and water saturated trunk barks of Abies balsamea and Picea mariana respectively.

The measurements plotted have been based on barks sampled in the former Erioderma habitat between Clam Harbour and Owls Head Harbour. The respective trees had been very healthy and had been growing under comparable conditions. Their DBH had been comparable at about 15 cm.