Monitoring and understanding climate-induced changes in the boreal and arctic vegetation is critical to aid in prognosticating their future. We used a 33 year (1982–2014) long record of satellite observations to robustly assess changes in metrics of growing season (onset: SOS, end: EOS and length: LOS) and seasonal total gross primary productivity. Particular attention was paid to evaluating the accuracy of these metrics by comparing them to multiple independent direct and indirect growing season and productivity measures. These comparisons reveal that the derived metrics capture the spatio-temporal variations and trends with acceptable significance level (generally p < 0.05). We find that LOS has lengthened by 2.60 d dec−1 (p < 0.05) due to an earlier onset of SOS (−1.61 d dec−1, p < 0.05) and a delayed EOS (0.67 d dec−1, p < 0.1) at the circumpolar scale over the past three decades. Relatively greater rates of changes in growing season were observed in Eurasia (EA) and in boreal regions than in North America (NA) and the arctic regions. However, this tendency of earlier SOS and delayed EOS was prominent only during the earlier part of the data record (1982–1999). During the later part (2000–2014), this tendency was reversed, i.e. delayed SOS and earlier EOS. As for seasonal total productivity, we find that 42.0% of northern vegetation shows a statistically significant (p < 0.1) greening trend over the last three decades. This greening translates to a 20.9% gain in productivity since 1982. In contrast, only 2.5% of northern vegetation shows browning, or a 1.2% loss of productivity. These trends in productivity were continuous through the period of record, unlike changes in growing season metrics. Similarly, we find relatively greater increasing rates of productivity in EA and in arctic regions than in NA and the boreal regions. These results highlight spatially and temporally varying vegetation dynamics and are reflective of biome-specific responses of northern vegetation during last three decades.
Department of Earth and Environment, Boston University, Boston, MA 02215, USA;Bay Area Environmental Research Institute, NASA Ames Research Center, Moffett Field, CA 94035, USA;Norwegian Institute for Nature Research, FRAM−High North Centre for Climate and the Environment, PO Box 6606 Langnes, N-9296 Tromsø, Norway;Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, Alaska, USA;Norut, PO Box 6434, N-9294 Tromsø, Norway;Norut, PO Box 6434, N-9294 Tromsø, Norway;Max Planck Institute for Meteorology, Hamburg, Germany;NASA Advanced Supercomputing Division, NASA Ames Research Center, Moffett Field, CA 94035, USA;Department of Earth and Environment, Boston University, Boston, MA 02215, USA
Recommended Citation:
Taejin Park,Sangram Ganguly,Hans Tømmervik,et al. Changes in growing season duration and productivity of northern vegetation inferred from long-term remote sensing data[J]. Environmental Research Letters,2016-01-01,11(8)