Evidence for A Weakening Relationship between Interannual Temperature Variability and Northern Vegetation Activity

Wednesday, 17 December 2014
Shilong Piao1, Huijuan Nan1, Chris Huntingford2, Philippe Ciais3, Pierre Friedlingstein4, Stephen Sitch4, Shushi Peng3, Anders Ahlström5, Josep Canadell6, Nan Cong1, Sam Levis7, Peter E. Levy8, Lingli Liu9, Mark Lomas10, Jiafu Mao11, Ranga Myneni12, Philippe P Peylin3, Benjamin Poulter3, Xiaoying Shi11, Guodong Yin1, Nicolas Viovy3, Tao Wang13, Xuhui Wang3, Soenke Zaehle14, Ning Zeng15, Zhenzhong Zeng1 and Anping Chen16, (1)Peking University, Beijing, China, (2)Centre for Ecology and Hydrology, Wallingford, United Kingdom, (3)CEA Saclay DSM / LSCE, Gif sur Yvette, France, (4)University of Exeter, Exeter, United Kingdom, (5)Lund University, Lund, Sweden, (6)CSIRO Marine & Atmospheric Res, Canberra, Australia, (7)National Center for Atmospheric Research, Boulder, CO, United States, (8)Center for Ecology and Hydrology Penicuik, Penicuik, United Kingdom, (9)IB Institute of Botany, Chinese Academy of Sciences, Beijing, China, (10)University of Sheffield, Sheffield, United Kingdom, (11)Oak Ridge National Lab, Oak Ridge, TN, United States, (12)Boston University, Boston, MA, United States, (13)Institut Pierre Simon Laplace, Paris, France, (14)Max Planck Institute for Biogeochemistry, Jena, Germany, (15)Univ Maryland, College Park, MD, United States, (16)Princeton University, Princeton, NJ, United States
Satellite derived Normalized Difference Vegetation Index (NDVI), a proxy of vegetation productivity, is known to be correlated with temperature in northern ecosystems. Here we show that above 30 oN, the strength of the relationship between the interannual variability of growing season NDVI and temperature (partial correlation coefficient RNDVI-GT) has declined substantially between 1982 and 2011, although with a heterogeneous spatial pattern. This decrease of RNDVI-GT is mainly observed in temperate and arctic ecosystems, and this phenomenon also partly reproduced by process-based ecosystem model results. In the northern temperate zone, the decrease of RNDVI-GT coincides with an increase of drought. In the arctic it may be related to a nonlinear response of photosynthesis to temperature, increase of hot extreme days, and shrub expansion over grass-dominated tundra. Our results caution the use of results from interannual time scales to constrain decadal response of plants to ongoing warming.