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  • 1
    Electronic Resource
    Electronic Resource
    Small-scale field mapping of lichen distribution in three dimensions with a computer-based position-tracking system (1999)
    Springer
    Oecologia 119 (1999), S. 552-556 
    Details
    ISSN: 1432-1939
    Keywords: Key words Electromagnetic Tracker ; Three-dimensional mapping ; Species composition ; Species distribution ; Topography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A trial was undertaken with an electromagnetic position-tracking (Tracker) system by mapping a small section of a lichen habitat near Cape Royds, Ross Island, Antarctica. This method facilitated the simultaneous collection of precise information about both the topography of the site and the distribution of lichen species. These data were used to produce accurate maps and three-dimensional reconstructions of the mapped area. The technique offers considerable savings in time over conventional methods used in plant and lichen surveys, and has potential to enhance the information collected from broader-scale transect surveys.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004420050818
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Chlorophyll a fluorescence and CO2 exchange of Umbilicaria aprina under extreme light stress in the cold (1998)
    Springer
    Oecologia 113 (1998), S. 325-331 
    Details
    ISSN: 1432-1939
    Keywords: Key wordsUmbilicaria aprina ; CO2 exchange ; Chlorophyll a fluorescence ; Low temperatures ; Photoinhibition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A lichen growing in a continental Antarctic region with low temperatures and strong irradiance in summer was investigated for evidence of photoinhibition. Field experiments with Umbilicaria aprina from a sheltered site with heavy snowpack showed no effects of photoinhibition when the lichen was exposed to strong sun irradiance for nearly 11 h a day. This was evident from CO2 exchange and simultaneous chlorophyll a fluorescence measurements. CO2 exchange was also not affected if quartz glass allowing greater UV penetration, was used as a lid for the cuvette. The dependency of net photosynthesis on photosynthetic photon flux density suggests that the lichen is photophilous.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004420050383
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Do secondary substances in the thallus of a lichen promote CO2 diffusion and prevent depression of net photosynthesis at high water content? (1997)
    Springer
    Oecologia 112 (1997), S. 1-3 
    Details
    ISSN: 1432-1939
    Keywords: Key words Lichen acid ; Lichen substances ; Photosynthesis ; Lichen ; Water content
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Many lichens show seriously depressed net photosynthesis (NP) at high thallus water contents due to increased carbon dioxide diffusion resistance through blockage of diffusion pathways by water. The soil lichen Diploschistes muscorum, however, shows no depression and NP is close to maximal even at the highest thallus water content. We investigated whether lichen substances (lecanoric and diploschistesic acids) in the cortex and medulla contributed to this ability to maintain high NP. Dry thalli were extracted with water-free acetone and, after this treatment, were found to be fully viable to the extent of continued growth after replanting in the field. No differences were found in the response of NP to thallus water content between the normal and extracted thalli, in fact the response curves were often nearly identical. Thus, in this species it seems that lichen substances did not maintain the water-free diffusion pathways and some other explanation, possibly structural, needs to be sought.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004420050275
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Microclimatic conditions, meltwater moistening, and the distributional pattern of Buellia frigida on rock in a southern continental Antarctic habitat (1998)
    Springer
    Polar biology 19 (1998), S. 101-106 
    Details
    ISSN: 1432-2056
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The importance of snowmelt as a source of moisture for the crustose lichen Buellia frigida in the early austral summer was investigated at Cape Geology, Granite Harbour, southern Victoria Land (77°01′S, 162°32′E). Surface and air temperatures and irradiance were recorded on the surface of a slightly inclined granite boulder for 5 weeks. Observations were made of lichen thallus hydration during a 5-day period. The results confirmed the strong warming effect of high irradiance; the rock surface and hydrated lichen were up to 19K above air temperature and, overall, the rock surface averaged 5.5K warmer. Therefore water condensation on the rock surface (dew or hoarfrost) was not possible during that period. Thalli were moistened by meltwater from both a small area of snow pack and from occasional snowfalls. The distribution of lichen thalli on the rock surface can be explained by the frequency and duration of meltwater moistening. Despite the very high irradiance whilst moist, the lichens seem well adapted to the combination of hydration, low temperatures and strong light.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003000050220
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    An assessment of the relationship between chlorophyll a fluorescence and CO2 gas exchange from field measurements on a moss and lichen (1998)
    Springer
    Planta 206 (1998), S. 611-618 
    Details
    ISSN: 1432-2048
    Keywords: Key words:Bryum (photosynthesis) ; Chlorophyll a fluorescence ; Electron transport ; Lichen (photosynthesis) ; Photosynthesis ; Respiration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. The relationship between CO2 exchange and relative electron-transport rate through photosystem II (ETR, measured using chlorophyll a fluorescence) was determined for a moss and a green algal lichen, photobiont probably Trebouxia sp., in the field in Antarctica. Net photosynthesis (NP) and dark respiration (DR) were measured over temperatures from zero to 25 °C and gross photosynthesis (GP) calculated (GP = NP + DR). The strong response of DR to temperature in these organisms resulted in substantial changes in CO2 exchange rates. The moss Bryum argenteum Hedw. showed a strong, linear relationship between GP and ETR. This was an unexpected result since mosses are C3 plants and, in higher plants, this group normally has a curvilinear GP versus ETR relationship. It is suggested that suppression of DR in the light might be involved. The lichen, Umbilicaria aprina Nyl., had nonlinear relationships between ETR and GP that were different at each measurement temperature. In some cases the lowest ETR was at the higher CO2 exchange rates. It is suggested that these relationships are the result of strong quenching mechanisms that are inversely proportional to GP. The results support a growing impression that the relationships between ETR and CO2 exchange are complex in these organisms and different from those found for higher plants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004250050439
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    Paper (German National Licenses)
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