AOBPreview originally published online on January 11, 2007
Annals of Botany 2007 99(2):345-353; doi:10.1093/aob/mcl266
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Total and Component Carbon Fluxes of a Scots Pine Ecosystem from Chamber Measurements and Eddy Covariance
1 Climate Research Division, Environment Canada, 11 Innovation Rd, Saskatoon SK, S7N 3H5, Canada
2 Faculty of Forestry and Environment, University of New Brunswick, Fredericton, NB, E3B 6C2, Canada
3 Urban Ecology and Restoration Key Laboratory, East China Normal University, 3663 North Zhongshan Rd, Shanghai 200062, China
4 Faculty of Forestry, University of Joensuu, PO Box 111, FIN-80101 Joensuu, Finland
* For correspondence. E-mail tianshan.zha{at}ec.gc.ca
Received: 17 July 2006 Returned for revision: 11 September 2006 Accepted: 23 October 2006 Published electronically: 11 January 2007
BACKGROUND AND AIMS: Distinguishing between, and quantifying, the different components of ecosystem C fluxes is critical in predicting the responses of ecosystem C cycling to climate change. The aims of this study were to quantify the photosynthetic and respiratory fluxes of a 50-year-old Scots pine (Pinus sylvestris) ecosystem, and to distinguish respiration of branches with needles from that of stems, and that of soil.
METHODS: The CO2 flux of the ecosystem was continuously measured using the eddy covariance (EC) method, and its components (respiration and photosynthesis of a branch with needles, stem and soil surface) were measured with an automated chamber system, from 2001 to 2004.
KEY RESULTS: All values below are chamber based. The average temperature coefficient (Q10) of respiration was 2·7, 2·2 and 4·0, respectively, for branch (Rbran), stem (Rstem) and the soil surface (Rsoil). Respiration at a reference temperature of 15 °C (R15) was 1·27, 0·49 and 4·02 µmol CO2 m–2 ground s–1 for the three components, respectively. Over 4 years, the annual Rbran, Rstem and Rsoil ranged from 196 to 256, 56 to 83 and 439 to 598 g C m–2 ground year–1, respectively, with a 4-year average of 227, 72 and 507 g C m–2 ground year–1. Annual ecosystem respiration (Reco) was 731, 783, 909 and 751 g C m–2 ground year–1 in years 2001–2004, respectively, gross primary production (GPP) was 922, 1030, 1138 and 1001 g C m–2 ground year–1, and net ecosystem production (NEP) was 191, 247, 229 and 251 g C m–2 ground year–1. The average contribution of Rbran, Rstem and Rsoil to Reco was 29, 9 and 62 %, respectively. Overstorey photosynthesis accounted for 96 % of GPP. The average Reco/GPP ratio was 0·78. Net primary production (NPP) in the 4 years was 469, 581, 600 and 551 g C m–2 year–1, respectively, with the NPP/GPP ratio 0·54 averaged over the years.
CONCLUSIONS: Respiration from the soil is the dominant component of ecosystem respiration. Differences between years in Reco were due to differences in temperature during the growing season. Rsoil was more sensitive to temperature than Rbran and Rstem, and differences in Rsoil were responsible for the differences in Reco between years.
Key words: Scots pine, carbon flux, stem, branch, soil, photosynthesis, respiration, ecosystem