Ecological controls on net ecosystem productivity of a mesic arctic tundra under current and future climates
Changes in arctic C stocks with climate are thought to be caused by rising net primary productivity (NPP) during longer and warmer growing seasons, offset by rising heterotrophic respiration (R<inf>h</inf>) in warmer and deeper soil active layers. In this study, we used the process model ecosys to test hypotheses for these changes with CO<inf>2</inf> and energy fluxes measured by eddy covariance over a mesic shrub tundra at Daring Lake, Canada, under varying growing seasons. These tests corroborated substantial rises in NPP, smaller rises in R<inf>h</inf>, and, hence, rises in net ecosystem productivity (NEP) from 17 to 45 g C m<sup>-2</sup> yr<sup>-1</sup> (net C sink), modeled with higher T<inf>a</inf> and longer growing seasons. However, NEP was found to decline briefly during midsummer warming events (T<inf>a</inf> > 20°C). A model run under climate change predicted for Daring Lake indicated that rises in NPP would exceed those in R<inf>h</inf> during the first 100 years, causing NEP to rise. Rises in NPP were driven by more rapid net N mineralization from more rapid R<inf>h</inf> in warming soils. However, greater declines in NEP were modeled during more frequent and intense midsummer warming events as climate change progressed. Consequently, average annual NEP (± interannual variability) rose from 30 (±13) g C m<sup>-2</sup> yr<sup>-1</sup> under current climate to 57 (±40) g C m<sup>-2</sup> yr<sup>-1</sup> after 90 years but declined to 44 (±51) g C m<sup>-2</sup> yr<sup>-1</sup> after 150 years, indicating that gains in tundra NEP under climate change may not be indefinite. Copyright 2011 by the American Geophysical Union. Copyright 2011 by the American Geophysical Union.
|Journal||Journal of Geophysical Research B: Solid Earth|
Grant, R.F., Humphreys, E, Lafleur, P.M., & Dimitrov, D.D. (2011). Ecological controls on net ecosystem productivity of a mesic arctic tundra under current and future climates. Journal of Geophysical Research B: Solid Earth, 116(1). doi:10.1029/2010JG001555