Effects of multiple environmental variables on tundra ecosystem respiration in maritime Antarctica

Summertime ecosystem respiration (ER) rates through seven sites were measured at an upland tundra on Fildes Peninsula in maritime Antarctica to investigate effects of topographic gradient, vegetation types and climatic factors on tundra ER rates. Overall the highest ER rates occurred at the tundra top, followed at the middle slope, and the lowest rates at the lower slope. The daily highest ER rates occurred at noon whereas the lowest at 6 am. There was a significant positive correlation (P < 0.05) between tundra ER and 0-10 cm soil temperature, but a significant negative correlation (P < 0.01) between ER and soil moisture. A high Q₁₀ value of 2.69 was obtained when all the data were combined, indicating soil temperature sensitivity of tundra ER. The mean ER at the tundra sites with moss coverage (72.2 ± 4.4 mg CO₂ m^-2 h^-1) was significantly higher (P < 0.01) than that at the sites with lichen coverage (46.8 ± 8.7 mg CO₂ m^-2 h^-1). The tundra sites without snow coverage experienced significant CO₂ release, whereas the emission through ER was very low at the tundra sites with snow coverage. Our results indicated that topographic gradient, soil temperature, soil moisture, vegetation types and snow coverage might affect tundra ER in maritime Antarctica.