Spatial and temporal variations in hectare-scale net CO2 flux, respiration and gross primary production of Arctic tundra ecosystems
Article first published online: 25 DEC 2001
Volume 14, Issue 2, pages 203–214, April 2000
How to Cite
Vourlitis, G. L., Harazono, Y., Oechel, W. C., Yoshimoto, M. and Mano, M. (2000), Spatial and temporal variations in hectare-scale net CO2 flux, respiration and gross primary production of Arctic tundra ecosystems. Functional Ecology, 14: 203–214. doi: 10.1046/j.1365-2435.2000.00419.x
- Issue published online: 25 DEC 2001
- Article first published online: 25 DEC 2001
- Received 20 January 1999; revised 29 July 1999;accepted 18 August 1999
- eddy covariance;
- global change;
1. Eddy covariance was used to measure the net CO2 flux of Alaskan moist-tussock and wet-sedge tundra ecosystems between 1 June and 31 August 1995. The sites were located within 2·5 km of each other and, depending on wind speed and thermal stability, the eddy-covariance measurements integrated surface fluxes over 0·8–26·5 ha (mean 3·8 ha) at the moist-tussock site and 0·1–4·2 ha (mean 0·6) at the wet-sedge site.
2. Both sites were net sinks for atmospheric CO2 during the 92-day measurement period but wet-sedge tundra accumulated 1·5 times more CO2 than moist-tussock tundra. Wet-sedge tundra was a net CO2 sink of −6·4 mol m−2 and moist-tussock tundra was a net sink of −4·6 mol m−2 over the June–August measurement period.
3. Estimates of whole-ecosystem respiration (R) were made using multiple non-linear regression by quantifying the response of measured nocturnal CO2 efflux (Fn) to fluctuations in air temperature and water-table depth (r2 = 0·68). Partial regression analysis revealed that water-table depth explained relatively more of the variance in Fn (45%) than temperature (11%). R was estimated to be 14·9 mol m−2 for moist-tussock tundra and 5·4 mol m−2 for wet-sedge tundra over the 92-day measurement period. The large difference in R was apparently owing to a substantially higher water table in wet-sedge tundra.
4. Estimated rates of gross primary production (GPP), calculated from measured net CO2 flux and estimated R, were 40% lower for wet-sedge tundra over the 92-day measurement period. Rates of GPP integrated over diel (24 h) periods were substantially larger for moist-tussock tundra ecosystems throughout June and July but during the month of August, total diel rates of GPP for moist-tussock and wet-sedge tundra were comparable.
5. Our results demonstrate that R and GPP of moist-tussock and wet-sedge tundra ecosystems can be reliably estimated from eddy-covariance measurements using functional relationships developed from plot-scale studies. Given the large spatial differences in hydrology, the larger sink observed for wet-sedge tundra was probably the result of relatively lower rates of R.