Håkon Holien

Growth of epiphytic old forest lichens across climatic and successional gradients

This paper aims to assess the influence of canopy cover on lichen growth in boreal forests along a regional forest gradient. Biomass and area gain, and some acclimation traits, were assessed in the ...

Acidity of boreal Picea abies-canopy lichens and their substratum, modified by local soils and airborne acidic depositions

Summary Lichens of the rare and predominantly epiphytic old forest community Lobarion were attached to Picea abies twigs with significantly higher bark pH (KCl) than members of the common and ubiquitous Pseudevernion community. The Lobarion species of spruce twigs, mainly members of the order Peltigerales, had distincly higher thallus pH than substratum pH, while the greenalgal Pseudevernion species, mainly belonging to the Lecanorales, were consistently more acidic than their substratum. pH of lichens and bark of P. abies twigs responded to a forest vegetation gradient reflecting the soil nutrient condition at the forest floor. However, the two groups of epiphytes seem to modify the bark pH in a way that enlarges a difference originally determined by soils in the root zone of the phorophyte. The lack of the Lobarion on spruce twigs in eastern Norway is probably a result of acid rain, as the bark and thallus pH in spruce canopies of eastern Norway appeared too low to support the Lobarion, even in stands with a species-rich epiphytic assemblage of alectorioid species.

Epiphytic lichen response to the edge environment in a boreal picea abies forest in Central Norway

Abstract This study has shown a clear edge effect on the green-algal lichen community on spruce branches in a middle boreal spruce forest. Measurements of the following parameters from lower tree branches were carried out at five transects parallel to the SE facing forest edge: species richness, lichen cover, proportion of morphologically aberrant thalli, and size distribution of Platismatia glauca, and length and number of pendulous thalli. The transects were located at 0, 8, 16, 32, and 64 m´s distance from the edge. The intensity of edge effects are found to be species-specific as some species showed pronounced edge response e.g., Cavernularia hultenii, Hypogymnia tubulosa, and Platismatia glauca. In general, the lichen pioneer community distributed on the outermost part of the spruce branches are most affected by the edge environment. A low frequency of small thalli of P. glauca and Bryoria spp. at the edge, compared to forest interior, may indicate unsuccessful colonization, depressed growth, or low supply of diaspores at the edge. Wind and snow abrasion at the edge are probably important factors explaining the observed lichen response.

Richness of epiphytic lichens in differently aged Picea abies plantations situated in the oceanic region of Central Norway.

Richness of epiphytic lichens in differently aged Picea abies plantations situated in the oceanic region of Central Norway

Size-dependent growth of two old-growth associated macrolichen species.

Relationships between thallus size and growth variables were analysed for the foliose Lobaria pulmonaria and the pendulous Usnea longissima with the aim of elucidating their morphogenesis and the factors determining thallus area (A) versus biomass (dry weight (DW) gain. Size and growth data originated from a factorial transplantation experiment that included three boreal climate zones (Atlantic, suboceanic and continental), each with three successional forest stands (clear-cut, young and old). When A was replaced by the estimated photobiont layer area in an area-DW scatterplot including all thalli (n = 1080), the two separate species clusters merged into one, suggesting similar allocation patterns between photobionts and mycobionts across growth forms. During transplantation, stand-specific water availability boosted area gain in foliose transplants, consistent with a positive role of water in fungal expansion. In pendulous lichens, A gain greatly exceeded DW gain, particularly in small transplants. The A gain in U. longissima increased with increasing DW:A ratio, consistent with a reallocation of carbon, presumably mobilized from the dense central chord. Pendulous lichens with cylindrical photobiont layers harvest light from all sides. Rapid and flexible three-dimensional A gain allows the colonization of spaces between canopy branches to utilize temporary windows of light in a growing canopy. Foliose lichens with a two-dimensional photobiont layer have more coupled A and DW gains.

Phylogeny of the genus Bryoria

The phylogenetic relationships of the genus Bryoria were examined using ITS, partial glyceraldehyde 3-phosphate dehydrogenase (GAPDH) and mitochondrial SSU rDNA sequence data in addition to 20 chemical and morphological characters. This first comprehensive molecular study to assess Bryoria phylogeny includes representatives from all the traditionally recognized four sections. Combined cladistic analyses of 88 Bryoria specimens representing at least 25 species resulted in highly resolved phylogenies. Based on the results, a new infrageneric classification for the genus is proposed. Five sections are recognized, largely corresponding to the existing classification, with the addition of section Americanae. The study shows that while most species with an erect growth-form are clearly monophyletic, current species status of many pendent taxa can be questioned.

LOGGING STRATEGY INFLUENCES COLONIZATION OF COMMON CHLOROLICHENS ON BRANCHES OF PICEA ABIES

Increased knowledge about how lichen colonization responds to logging is a prerequisite for developing guidelines in forest management aimed to maintain biodi- versity. Within an experimentally logged boreal spruce forest we studied effects of different logging strategies and distance to the forest edges on colonization of epiphytic chlorolichens. Within a fine-grained (23 clearcuts, 0.2 ha each) and a coarse-grained area (3 clearcuts, 2.25 ha each) we sampled 90 branches. In addition 20 branches were sampled in an un- touched control area. The 15 youngest annual shoots along the main axes on each branch were analyzed. Establishment of the dispersed diaspores, most of them Hypogymnia, was mainly limited to shoot ages 4-6 where the needles also were present. Independent of logging strategy the occurrence of small lobules increased with increasing distance from the edges, indicating unfavorable conditions for establishment at the edges or a lower supply of diaspores. A distinct decrease in the number of thalli of Cavernularia hultenii was observed in the two logged areas compared to the control branches. The colonization of Hypogymnia spp. and Platismatia spp. was successful in the fine-grained area, while a coarse-grained pattern of logging caused a significant decrease in the number of thalli, from shoot age 5 for Hy- pogymnia and shoot age 9 for Platismatia. An early drop of needles in the coarse-grained area, especially at the forest edges, supports the assumption that the occurrence of needles is important for a successful colonization. A higher rate of growth of these species in the coarse-grained area, compared to the other two areas, illustrates that logging does not necessarily cause unfavorable conditions for growth of already established thalli. In conclusion, establishment of the diaspores is less successful in logged areas. Thus, a fragmented logging pattern influences the colonization negatively, even for common chlorolichens. Moreover, the response to logging strategy is species-specific. Development of management guidelines should be based on wide scientific knowledge about the species life-history characteristics.

Taxonomy of Bryoria Section Implexae (Parmeliaceae, Lecanoromycetes) in North America and Europe, Based on Chemical, Morphological and Molecular Data

Ninety-seven ingroup specimens of Bryoria section Implexae (Parmeliaceae, Lecanoromycetes) were studied using molecular, chemical, morphological and geographic characters. The molecular data included nuclear ribosomal markers (ITS, IGS) and the partial glyceraldehyde-3-phosphate dehydrogenase (GAPDH) gene. In addition to parsimony analyses, a haplotype network was constructed. Phylogenetic analyses strongly supported the monophyly of the section Implexae. The specimens were grouped into two monophyletic clades. Clade 1 encompassed all esorediate material from North America, whereas Clade 2 included both sorediate North American material and all European material. Relationships at the species level, however, remained unresolved, except in the case of North American B. implexa chemotype 1 and European B. capillaris. Nevertheless a number of species in each clade can be recognized using traditional morphological, chemical and ecological characters: Bryoria friabilis, B. inactiva sp. nova, B. kockiana sp. nova (supported also by phylogeny), B. pikei and B. pseudofuscescens in Clade 1, and B. capillaris, B. fuscescens, B. implexa, B. kuemmerleana, and B. vrangiana in Clade 2. In addition, North American B. capillaris is proposed for inclusion in B. pikei, while B. chalybeiformis, B. lanestris and B. subcana are used as synonyms of B. fuscescens.

Genetic structure in a fragmented Northern Hemisphere rainforest: large effective sizes and high connectivity among populations of the epiphytic lichen Lobaria pulmonaria

An extraordinary diversity of epiphytic lichens is found in the boreal rainforest of central Norway, the highest‐latitude rainforest in the world. These rainforest relicts are located in ravine systems, and clear cutting has increased the distance between remaining patches. We hypothesized that the relatively small lichen populations in the remaining forest stands have suffered a depletion of genetic diversity through bottlenecks and founder events. To test this hypothesis, we assessed genetic diversity and structure in the populations of the tripartite lichen Lobaria pulmonaria using eight SSR loci. We sampled thalli growing on Picea abies branches and propagules deposited in snow at three localities. Contrary to expectations, we found high genetic diversity in lichen and snow samples, and high effective sizes of the studied populations. Also, limited genetic differentiation between populations, high historical migration rates, and a high proportion of first generation immigrants were estimated, implying high connectivity across distances <30 km. Almost all genetic variation was attributed to variation within sites; spatial genetic structures within populations were absent or appeared on small scales (5–10 m). The high genetic diversity in the remaining old boreal rainforests shows that even relict forest patches might be suitable for conservation of genetic diversity.

High fungal selectivity for algal symbionts in the genus Bryoria

In this study we examined photobiont identity, diversity and selectivity in the genus Bryoria . We focused on B. fremontii and section Implexae in order to determine whether secondary chemistry is correlated with photobiont identity. DNA from two loci for photobionts and three loci for mycobionts was sequenced for both parsimony and Bayesian phylogenetic analyses. A comparison of photobiont and mycobiont phylogenies reveals that most Bryoria species associate exclusively with lineages of the Trebouxia simplex group; only B. smithii was associated with a different photobiont. We conclude that most Bryoria species included in our study are highly selective in their choice of algal partners and that the presence/concentration of different secondary compounds does not correlate with photobiont identity either in section Implexae or in B. fremontii .