The major physiognomic and ecological categories of the lichen-rich, epigeic communities in the boreal (taiga) and arctic (tundra) zones are defined and their syntaxonomy and ecology in Europe, Asia and North America is reviewed. In the boreal and hemiarctic areas open, dry, acidophytic lichen woodlands are widespread, especially on sandy habitats. Their epigeic lichen synusiae are usually dominated by four fruticoseCladina species, being extremely homogeneous in species composition and structure throughout the boreal zone, while the dominant trees and the other vascular plant flora of the woodlands are geographically more variable. No phytosociological classification system exists that would cover most of these communities over the circumpolar regions. Very similar communities, though much more poorly known, are found on thin soils over Precambrian rock outcrops. Other sites to produce epigeic lichen communities include open sand dunes, treeless heathlands, drier bogs and many seral stages, like those on road banks. Boreal lichen-rich communities on eutrophic soils may be developed in semiarid regions, in particular. In the Arctic, lichens are common in most communities, and the driest ones are regularly lichen-dominated, whether acidophytic or eutrophytic, chionophytic or achionophytic. Detailed syntaxonomic systems for their classification have been developed, especially in Greenland and Scandinavian mountains (in oroarctic zones in the latter regions). The richest fruticose lichen areas are in continental, hemiarctic timberline regions in northern Siberia and Canada. The southern and middle arctic subzones are also characterized by many macrolichens, such asCetraria cucullata, C. nivalis, Alectoria ochroleuca, andThamnolia vermicularis, but everywhere also small, crustose lichens are common on soil, such asRinodina turfacea andLopadium pezizoideum, which are often overlooked in vegetation analyses. The presence of microlichens and the formation of mosaic micropatterns of soil lichen communities is particularly typical of the northern arctic subzone. The conservation problems of the boreal and arctic lichen communities include overgrazing by reindeer or caribou, which has caused delichenization in some regions, extensive forest and tundra fires, use of heavy transport vehicles in forestry and tundra operations, and, locally, heavy industrial air pollution.

Epigeic lichen communities of taiga and tundra regions

Concentrations of NH4+, NO3−, PO43−, K+, Ca2+ and Mg2+ in snow meltwater resulting from summer snow showers were monitored before and after its passage through monospecific stands of the Antarctic macrolichen Usnea sphacelata R. Br. The sampling was conducted under field conditions near Casey Station in East Antarctica between January and March. Total snow deposition during the 61-d period was 44±1 mm (rainfall equivalent depth) delivering 362±10, 87±2 and 9±1 μmol m−2 of NH4+, NO3− and PO43−, respectively. Meltwater that had percolated through U. sphacelata was depleted in NH4+ and NO3− equating with a retention by the lichen of 87 and 92%, respectively, of the total wet deposition of these ions. Lichen-modified meltwater was slightly enriched in PO43−, but because the volume of the lichen percolate was smaller than that of the original snow deposition, the lichen achieved a net gain of 9% of the total P deposited. Lichen percolate was also enriched in metal cations. Potassium loss associated with the melting of the heaviest snowfall (18 mm) was equivalent to only 0·05% of the total K in the lichen suggesting that ion loss did not signal significant cellular damage. There was also a progressive increase in NH4+ concentration in unmodified meltwater from 3 to 21 nmol ml−1 over a 3-d period whereas levels in the lichen-modified meltwater remained unchanged at 4 nmol ml−1. This enrichment in NH4+ might have resulted from dry deposition onto the melting snow pack of NH3 emitted from nearby penguin rookeries. During the study, tagged thalli of U. sphacelata made a 2% loss in dry mass although they appeared healthy and, at the end of the study, showed an effective quantum yield (ΔF/Fm′) comparable with field material. The results are discussed in relation to the time of year that is likely to be most suitable for lichen growth in this continental Antarctic environment and the potential growth-led demand for N in U. sphacelata.

Nutrient exchange in an Antarctic macrolichen during summer snowfall–snow melt events

Understanding potential impacts of vegetation change on caribou energetics requires information on variations in forage quality among different plant types and over time. We synthesized data on forage quality (nitrogen, neutral detergent fiber and dry matter digestibility) for 10 plant growth forms from existing scientific literature and from field research in the Arctic National Wildlife Refuge, Alaska. These data describe forage quality of plant species in habitats found within the summer and winter range of the Porcupine caribou herd in northwestern Canada and northern Alaska, U.S.A. We compared mean levels of summer forage quality among growth forms and, where possible, estimated seasonal changes in forage quality. Preferred forage groups (deciduous shrubs, forbs, and cottongrass flowers) had higher nitrogen and digestibility, and lower fiber content, than other growth forms. Nitrogen concentration in green biomass peaked at the onset of the growing season in forbs and deciduous shrubs, whereas graminoids reached peak nitrogen concentrations approximately 15-30 days after growth initiation. In vitro dry matter digestibility (IVDMD) and concentration of neutral detergent fiber (NDF) of green biomass differed among growth forms, but did not show strong seasonal changes. IVDMD and NDF concentrations were correlated with nitrogen concentrations in studies that had paired sampling.

https://septentrio.uit.no/index.php/rangifer/article/download/693/658

Variations in plant forage quality in the range of the Porcupine caribou herd

Estimates of carbon gain were obtained based upon integration of previously published measurements of diel courses of CO2 exchange of seven lichen species in their natural tundra habitat. Total net photosynthetic CO2 uptake, CO, loss by dark respiration, and the balance between these were calculated. The field measurements (146 observations of lichen sample diel courses on 26 d distributed over the growth periods from July through September in 1988 and 1989) were classed with respect to 5 types of weather conditions. The occurrence of these weather types during the growing season was established according to meteorological data. Combination of these data sets permits an estimate of seasonal carbon gain. Integrated photosynthetic carbon uptake was highest for the cyanobacterial Peltigera malacea, 1.5 times higher than for Dactylina arctica and 5 times higher than for the least productive Masonhalea richardsonii, both being green algal species. There was an essentially linear correlation across species between the sum of carbon uptake and short-term maximal rates of net photosynthesis, stressing the importance of photosynthetic capacity for carbon gain. Mean respiratory carbon loss for all of the species was ca. 33%. Three groups of species were determined with respect to estimated seasonal carbon balance: high productivity (carbon gain of 24.0-21.5% of thallus carbon content) which included D. arctica, P. malacea, P. aphthosa, and Thamnolia vermicularis, lowest productivity (6.8%) for M. richardsonii, and intermediate for Cetraria cucullata (15.9%) and Stereocaulon alpinum (14.6%). Seasonal carbon gain is related to the maximal possible thallus growth. Estimates of annual lichen biomass increase in typical tundra communities ranged from 47.2 gDW m-2 for

https://www.jstor.org/stable/pdfplus/1551972.pdf

Upland tundra in the foothills of the Brooks Range, Alaska, U.S.A.: lichen long-term photosynthetic CO2 uptake and net carbon gain

The study of climate change and air pollution is very important in present circumstances throughout the world. Several methods including biological methods are being used for monitoring of environment to assess the climate and air pollution vulnerability. Among the biological methods the use of lichens as a bio-indicator has been very popular for such studies. Lichen, being a natural indicator of climate change and air pollution effects, is very useful for these studies particularly in mountain region. Therefore, a review of the work done in different parts of the world to study the climate change, air pollution and heavy metals using lichen as natural indicator has been presented and the gap areas have been identified for further studies in connection to climate change and air pollution vulnerability using lichen as an indicator.

http://www.isca.in/IJENS/Archive/v4/i12/14.ISCA-IRJEVS-2015-217.pdf

Lichen as a Bio-Indicator Tool for Assessment of Climate and Air Pollution Vulnerability: Review

Lichens are a constant, though variable, component of arctic tundra ecosystems (Wielgolaski, 1972, 1975). In the Barrow tundra lichens have been reported as a minor part of the vegetation (Britton, 1967; Spetzman, 1959; Wielgolaski, 1972). We have examined the lichens in the vicinity of Barrow and have attempted to quantify their occurrence, biomass, and productivity, as well as to discover the relationships of lichens to their microenvironments. We measured the elemental contents of selected lichens and their substrates in an attempt to discover if significant mineral accumulation was occurring in the lichens.

The Role of Lichens in the Structure, Productivity, and Mineral Cycling of the Wet Coastal Alaskan Tundra

http://link.springer.com/content/pdf/10.1007/978-1-4612-6307-4_7.pdf

7. The Role of Lichens in the Structure, Productivity, and Mineral Cycling of the Wet Coastal

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The Role of Lichens in the Structure, Productivity, and Mineral Cycling of the Wet Coastal Alaskan Tundra

7. The Role of Lichens in the Structure, Productivity, and Mineral Cycling of the Wet Coastal