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Citation

Novis PM, Whitehead D, Gregorich EG, Hunt JE, Sparrow AD, Hopkins D & Elberling B (2007) Annual carbon fixation in terrestrial populations of Nostoc commune (Cyanobacteria) from an Antarctic dry valley is driven by temperature regime. Global Change Biology, 13 (6), pp. 1224-1237. http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2486.2007.01354.x/pdf; https://doi.org/10.1111/j.1365-2486.2007.01354.x

Abstract
Nostoc commune Vaucher (a cyanobacterium) is a very conspicuous terrestrial primary producer in Victoria Land, continental Antarctica. Because polar ecosystems are considered to be especially sensitive to environmental changes, understanding the environmental constraints on net carbon (C) fixation by N. commune is necessary to determine the effects of environmental changes on the ecological functioning of ice-free areas of the continent. A model describing net C fixation in terrestrial populations of N. commune in an Antarctic dry valley was constructed using field and laboratory measurements in which N. commune colonies were exposed to different combinations of incident irradiance (400-700 nm), temperature, and degree of desiccation. For desiccated N. commune mats with water content 30% saturation, rates of net C fixation and dark respiration depended strongly on irradiance and temperature. Net C fixation reached a maximum rate of 21.6 mu g C m (- 2) s (- 1) at irradiance of approximately 250 mu mol m (- 2) s(- 1) and the optimum temperature of 20.5 degrees C. Agreement between predicted short-term net C fixation and field and laboratory measurements allowed estimation of total seasonal fixation, using previously published environmental data. Annual net C fixation was estimated in the range 14.5-21.0 g C fixed m (- 2) Nostoc mat, depending on year/season. Estimates for different seasons correlated with thermal time (accumulated hours above 0 degrees C during the year) rather than irradiance, in contrast to communities in local lacustrine environments, where irradiance is the main driver of primary productivity. In the terrestrial habitat, N. commune appears to compromise between an ability to capitalize on short periods of higher temperature and efficient utilization of lower irradiance at low temperature. The relationship between thermal time and net annual C fixation by N. commune is strongly linear.

Keywords
250; ABILITY; AGREEMENT; Antarctic; AREAS; C; CARBON; COMBINATION; Communities; community; constraints; data; ECOSYSTEM; ECOSYSTEMS; environment; environments; Estimation; FIELD; functioning; habitat; Laboratories; LAND; Measurement; model; PERIOD; Population; POPULATIONS; primary; RANGE; RATES; REGIME; relationship; RESPIRATION; TEMPERATURE; time; understanding; WATER

Journal
Global Change Biology: Volume 13, Issue 6