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Moisture effects on temperature sensitivity of CO2 exchange in a subarctic heath ecosystem

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Author

  • L Illeris
  • Torben Christensen
  • Mikhail Mastepanov

Summary, in English

Carbon fluxes between natural ecosystems and the atmosphere have received increased attention in recent years due to the impact they have on climate. In order to investigate independently how soil moisture and temperature control carbon fluxes into and out of a dry subarctic dwarf shrub dominated heath, monoliths containing soil and plants were incubated at three different moisture levels and subjected to four different temperature levels between 7 and 20degreesC. Ecosystem CO2 exchange was monitored continuously day and night during the 16 to 18 days that each of three experiments lasted. Additionally, the carbon allocation pattern of the plants was investigated by labelling monoliths with (CO2)-C-14 followed by harvest of above and below ground plant parts. The results revealed that the three different soil moisture levels caused distinctly differing levels Of CO2 fluxes. Also, both carbon fixation calculated as gross ecosystem production (GEP) and carbon release measured as ecosystem respiration (ER) increased with increasing temperatures, with ER increasing faster than GER Hence, short term carbon loss from the ecosystem accelerated with raised temperatures. Temperature sensitivity of the ecosystem was dependent on the soil moisture level, shown by differing Q(10) values of both GEP and ER at different soil moisture levels. It is therefore highly important to take soil moisture levels into consideration when evaluating responses of ecosystem carbon balance to changes in temperature. The greatest C fixation took place via the two most dominant species of the ecosystem, Vaccinium uliginosum and Empetrum hermaphroditum, with the former being responsible for the different size of C fixation at the three moisture levels.

Publishing year

2004

Language

English

Pages

315-330

Publication/Series

Biogeochemistry

Volume

70

Issue

3

Document type

Journal article

Publisher

Springer

Topic

  • Physical Geography

Keywords

  • soil respiration
  • soil moisture
  • dry tundra
  • Arctic
  • carbon flux
  • temperature sensitivity

Status

Published

ISBN/ISSN/Other

  • ISSN: 1573-515X