HR: 0830h
AN: GC31B-0185    [PDF]
TI: Long-term pattern of and controls on intra and inter-seasonal variability in net ecosystem CO2 exchange over wet coastal sedge tundra
AU: * Kwon, H
EM: hkwon@sciences.sdsu.edu
AF: Global Change Research Group, Department of Biology, San Diego State University, 5500 Campanile Dr., San Diego, CA 92182 United States
AU: Oechel, W C
EM: oechel@sunstroke.sdsu.edu
AF: Global Change Research Group, Department of Biology, San Diego State University, 5500 Campanile Dr., San Diego, CA 92182 United States
AU: Zulueta, R C
EM: zulueta@mail.sdsu.edu
AF: Global Change Research Group, Department of Biology, San Diego State University, 5500 Campanile Dr., San Diego, CA 92182 United States
AU: Hastings, S J
EM: shasting@sunstroke.sdsu.edu
AF: Global Change Research Group, Department of Biology, San Diego State University, 5500 Campanile Dr., San Diego, CA 92182 United States
AB: Measurement of net ecosystem CO2 exchange (NEE) was made on a wet coastal sedge tundra ecosystem in Barrow, Alaska over the growing seasons (June 1 to August 31) between 1999 and 2002 using the eddy covariance technique. The objectives of this study were to quantify the seasonal carbon budget and intra- and inter-seasonal variability of carbon flux as well as examining the control mechanisms on NEE. Climatic conditions changed from year to year, with seasonal average air temperature varying from 1.6 oC to 3.0 oC, precipitation from 57.8 mm to 86.8 mm, and soil moisture content varying 0.40 m3 m-3 to 0.76 m3 m-3. The 2002 growing season recorded the earliest snow-melt (day 144) among the study years which extended a the length of the growing season by 20 days compared to the other three years. Due to the early snow-melt and rapid development of the plant canopy in 2002, considerable carbon uptake took place shortly after the initiation of growth with a peak NEE of - 2.3 gC m-2 d-1 on day 166, while the maximum carbon uptake (ie. -5.4 gC m-2 d-1 in 1999, - 2.8 gC m-2 d-1 in 2000, and - 2.9 gC m-2 d-1 in 2001) occurred in the main growing season during the rest of years. An unusual long period of cold air temperature ( ~ 0 oC) from day 170 to day 190 in 2002 resulting in a reduction in the magnitude of the carbon uptake and changed the ecosystem from a sink to a source. This result may occurred due to the compound effects of restrained plant growth and phenological development and suggests the temperature sensitivity of the wet coastal sedge tundra ecosystem during the early growing season. Although precipitation and soil moisture content varied throughout the growing seasons, the NEE in wet coastal sedge tundra ecosystem was not effected by the changes in precipitation and soil moisture content due to adequate levels of water availability all four years. The wet coastal sedge tundra ecosystem accumulated a total of 70. 0 gC m-2 season-1, 46.6 gC m-2 season-1, 51.7 gC m-2 season-1 and 60.8 gC m-2 season-1 during over the 1999, 2000, 2001 and 2002 growing seasons respectively. These results indicate that an increase in the growing season may not necessarily cause an increase in the sequestration of carbon by the ecosystem owing to the compound mechanisms controlling ecosystem CO2 exchange.
DE: 0315 Biosphere/atmosphere interactions
SC: Global Climate Change [GC]
MN: 2003 Fall Meeting