Spatial and temporal variations in hectare‐scale net CO 2 flux, respiration and gross primary production of Arctic tundra ecosystems

• Published in: Functional Ecology
• Main Authors: Vourlitis, G. L., Harazono, Y., Oechel, W. C., Yoshimoto, M., Mano, M.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2000
• Subjects: Arctic; Tundra
• Online Access: http://dx.doi.org/10.1046/j.1365-2435.2000.00419.x; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1046%2Fj.1365-2435.2000.00419.x; https://besjournals.onlinelibrary.wiley.com/doi/pdf/10.1046/j.1365-2435.2000.00419.x

Abstract 1. Eddy covariance was used to measure the net CO 2 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 CO 2 during the 92‐day measurement period but wet‐sedge tundra accumulated 1·5 times more CO 2 than moist‐tussock tundra. Wet‐sedge tundra was a net CO 2 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 CO 2 efflux ( F n ) to fluctuations in air temperature and water‐table depth ( r 2 = 0·68). Partial regression analysis revealed that water‐table depth explained relatively more of the variance in F n (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 CO 2 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 ...