| The Arctic has experienced rapid warming with increased precipitation projected to accompany future warming. In response, patterns and magnitudes of gross ecosystem photosynthesis (GEP), ecosystem respiration (ER) and the net ecosystem exchange of CO2 (NEE) are expected to shift. To explore potential future responses, a long-term, multilevel, multifactor climate change experiment was established in northwest Greenland. The experiment showed low-level warming increased the magnitude of the ecosystem C sink; high-level warming made the ecosystem a source of C to the atmosphere; and when high-level warming was combined with increased summer rain, the ecosystem became a C sink. ER modeling revealed the importance of soil moisture as a driving variable, and community composition and proxies for leaf-level physiology suggest that GEP responses reflect ecosystem-level changes rather than leaf-level changes. Findings indicated that the sign and magnitude of the future High Arctic C budget may ultimately depend upon changes in summer rainfall. |
