Abstract
While substantial cold-season respiration has been documented in most arctic and alpine ecosystems in recent years, the significance of cold-season photosynthesis in these biomes is still believed to be small. In a mesic, subartic heath during both the cold and warm season, we measured in situ ecosystem respiration and photosynthesis with a chamber technique at ambient conditions and at artificially, increased frequency of freeze-thaw (FT) cycles during fall and spring. We fitted the measured ecosystem exchange rates to respiration and photosynthesis models with R-2-values ranging from 0.81 to 0.85. As expected, estimated cold-season (October, November, April and May) respiration was significant and accounted for at least 22% of the annual respiratory CO2 flux. More surprisingly, estimated photosynthesis during this period accounted for up to 19% of the annual gross CO2 uptake, suggesting that cold-season photosynthesis partly balanced the cold-season respiratory carbon losses and can be significant for the annual cycle of carbon. Still, during the full year the ecosystem was a significant net source of 120 +/- 12g Cm-2 to the atmosphere. Neither respiration nor photosynthetic rates were much affected by the extra FT cycles, although the mean rate of net ecosystem loss decreased slightly, but significantly, in May. The results suggest only a small response of net carbon fluxes to increased frequency of FT cycles in this ecosystem
| Originalsprog | Engelsk |
|---|---|
| Tidsskrift | Global Change Biology |
| Vol/bind | 13 |
| Udgave nummer | 7 |
| Sider (fra-til) | 1498-1508 |
| Antal sider | 11 |
| ISSN | 1354-1013 |
| Status | Udgivet - 2007 |
Emneord
- alpine
- ALPINE ECOSYSTEM
- AMBIENT
- arctic
- Arctic and alpine ecosystem
- atmosphere
- Carbon
- carbon flux
- chamber
- CO2
- CO2 flux
- CO2 FLUXES
- CO2 PRODUCTION
- cold season
- dwarf-shrubs
- ECOSYSTEM
- ecosystem photosynthesis
- Ecosystem respiration
- ECOSYSTEMS
- EXCHANGE
- FALL
- flux
- FLUXES
- freeze-thaw
- FREEZE-THAW CYCLES
- graminoids
- heath
- IN-SITU
- increased freeze-thaw cycles
- MODEL
- modelled annual carbon budget
- MODELS
- MOSSES
- N2O
- NET CARBON
- Nitrogen
- northern sweden
- passive cold-season warming
- photosynthesis
- RATES
- respiration
- SEASON
- source
- spring
- subarctic
- Sweden
- TAIGA SOILS
- TEMPERATURES
- tundra
- variability
- WINTER CO2