Responses of moss and lichen vegetation to manipulated warming: Long-term study exploiting OTC approach at James Ross Island, Antarctica
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|MU Faculty or unit
|In 2007, several open top chambers (OTCs) were establised in three contrasting habitats: i) mossdominated coastal vegetation oasis (5 m a.s.l.), (ii) lichen-dominated plateau of a table mountain (350 m a.s.l.), and ice-free forefield of a cap glacier (410 m a.s.l.). The long-term study comprised evaluation of differences in microclimate between the OTCs and outside control plots as well as changes in vegetation cover and selected photosynthetic characteristics. For consecutive 7 years, continuous measurements of air temperature (30 cm above surface), vegetation cover and soil temperatures as well as air humidity have been done at the three habitats in 1 h interval. Vegetation in OTCs and at control plots were photographed each year so that OTCs-induced changes in vegetation cover could be evaluated. To estimate annual courses of photosynthetic activity of Bryum sp., a common moss species at the coastal plot, fluorometers were installed in OTCs and at contol plot to measure an effective quantum yield of photosynthetic processes in photosystem II. Additionally, numerous physiological measurements, such as e.g. responses to dehydration, high light and low temperature have been carried out on collected mosses and lichens in a laboratory under controlled conditions. Microclimatological measurements showed that mean annual air temperature increment in OTCs was lower for coastal plot than lichen-dominated table mountain plateau. However, positive vegetation response was found only for coastal plot. Similarly, soil temperature (5 cm depth) was OTC-affected in both habitats which may have consequences for soil microbial activity. Vegetation cover area increased in OTCs located at coast due to OTCs-affected growth of mosses. However, vegetation area was partly affected by episodic depositions of mineral particles transported by a strong wind from ice- and snow-free areas during austral summers. This resulted in a burrial of vegetation under several mm-thick layer. Lichen vegetation in OTCs located on a table mountain remained unaffected by elevated temperature. Chlorophyll fluorescence data revealed temperature-induced inhibition of Bryum sp. photosynthesis at the beginning of austral winter and several short-term episodes during winter when the moss is physiologically-active due to above-zero temperature. During summer season, data indicated water limitation and resulting inhibition of photosynthesis in Bryum sp. sensitively. The authors thank CzechPolar facility.