Open AccessEcological controls on net ecosystem productivity of a mesic arctic tundra under current and future climates
Author(s) -
Grant R. F.,
Humphreys E. R.,
Lafleur P. M.,
Dimitrov D. D.
Publication year - 2011
Publication title -
journal of geophysical research: biogeosciences
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2010jg001555
Subject(s) - tundra , primary production , environmental science , climate change , eddy covariance , ecosystem , arctic , growing season , atmospheric sciences , productivity , ecosystem respiration , global warming , ecology , climatology , biology , economics , macroeconomics , geology
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 h ) in warmer and deeper soil active layers. In this study, we used the process model ecosys to test hypotheses for these changes with CO 2 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 h , and, hence, rises in net ecosystem productivity (NEP) from 17 to 45 g C m −2 yr −1 (net C sink), modeled with higher T a and longer growing seasons. However, NEP was found to decline briefly during midsummer warming events ( T a > 20°C). A model run under climate change predicted for Daring Lake indicated that rises in NPP would exceed those in R h during the first 100 years, causing NEP to rise. Rises in NPP were driven by more rapid net N mineralization from more rapid R h 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 −2 yr −1 under current climate to 57 (±40) g C m −2 yr −1 after 90 years but declined to 44 (±51) g C m −2 yr −1 after 150 years, indicating that gains in tundra NEP under climate change may not be indefinite.