Olga Hilmo

Colonization of old-forest lichens in a young and an old boreal Picea abies forest: an experimental approach

Abstract Understanding the factors limiting the distribution of a species is crucial for designing conservation strategies. We evaluated whether the scarcity of old-forest lichens in young forests was due to unfavourable environmental conditions for colonization in young stands or to dispersal limitations. Vegetative diaspores of Lobaria scrobiculata , Platismatia glauca and Platismatia norvegica were sown on 240 spruce twigs transplanted to a young and an old stand of spruce. Our results demonstrate that the old-forest species established and grew as rapidly in the young as in the old forest. Higher light levels in the young, compared with the old forest, did not reduce diaspore development. Moreover, greater numbers of juvenile thalli of Platismatia were found on control twigs (unsown) in the old forest, compared with the young forest, suggesting higher propagule density and more efficient dispersal in the old stand. Our results indicate that life-history characteristics, which include dispersal characters, are important for explaining the species scarcity in younger stands. Minimizing the distance between regeneration units and potential sources of propagules is probably important for maintaining lichen biodiversity in managed forest ecosystems.

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 ...

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.

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.

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.