This article explores differences in allocation and turnover of assimilated carbon in two Subarctic tundra communities.

Climatic changes in Arctic regions are likely to have significant impacts on vegetation composition and physiological responses of different plant types, with implications for the regional carbon (C) cycle.

The authors used an in situ ¹³C pulse at mid-summer in Swedish Lapland to investigate C allocation and turnover in four contrasting tundra plant communities. They found a high rate of turnover of assimilated C in leaf tissues of Betula nana and graminoid vegetation at the height of the growing season, with a mean residence time of pulse-derived ¹³C of 1.1 and 0.7 days, respectively.

One week after the pulse, c. 20 and 15%, respectively, of assimilated label-C remained in leaf biomass, representing most likely allocation to structural biomass. For the perennial leaf tissue of the graminoid communities, a remainder of approximately 5% of the pulse-derived C was still traceable after 1 year, whereas none was detectable in Betula foliage.

The results indicate a relatively fast C turnover and small belowground allocation during the active growing season of recent assimilates in graminoid communities, with comparatively slower turnover and greater investment in belowground allocation by B. nana vegetation.

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