Temperature response of CO2 exchange and dissolved organic carbon release in a maritime Antarctic tundra ecosystem
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We examined the temperature response of CO2 exchange and soil biogeochemical processes in an Antarctic tundra ecosystem using laboratory incubations of intact tundra cores. The cores were collected from tundra near Anvers Island along the west coast of the Antarctic Peninsula that was dominated by the vascular plants Colobanthus quitensis and Deschampsia antarctica. After the initial 8-week incubation at moderate growth temperatures (12/7°C, day/night), the tundra cores were incubated for another 8 weeks at either a higher (17/12°C) or lower (7/4°C) temperature regime. Temperature responses of CO2 exchange were measured at five temperatures (4, 7, 12, 17, and 27°C) following each incubation and soil leachates were collected biweekly over the second incubation. Daytime net ecosystem CO2 exchange (NEE) per unit core surface area was higher across the five measurement temperatures after the warmer incubation (17/12°C > 7/4°C). Responses of ecosystem respiration (ER) were similar at each measurement temperature irrespective of incubation temperature regimes. ER, expressed on a leaf-area basis, however, was significantly lower following the warmer incubation, suggesting a downregulation of ER. Warmer incubation resulted in a greater specific leaf area and N concentration, and a lower δ13C in live aboveground C. quitensis, but a higher δ13C in D. antarctica, implying species-specific responses to warming. Concentrations of dissolved organic C and N and inorganic N in soil leachates showed that short-term temperature changes had no noticeable effect on soil biogeochemical processes. The results suggest that downregulation of ER, together with plant species differences in leaf-area production and N use, can play a crucial role in constraining the C-cycle response of Antarctic tundra ecosystems to warming.
KeywordsGross Primary Production Antarctic Peninsula Ecosystem Respiration Dissolve Organic Carbon Production Dissolve Organic Carbon Release
We thank Sarah Strauss and Dr. Christopher Ruhland for assistance in field collection and chemical analysis. Special thanks goes to Drs. Christopher Ruhland and David Bryant for their helpful comments on an earlier version of this manuscript. The administrative and logistical support of personnel at Palmer Station is gratefully acknowledged. This work was supported by NSF grant OPP-0230579.
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