Spatial and Temporal Variation in Primary Productivity (NDVI) of Coastal Alaskan Tundra: Decreased Vegetation Growth Following Earlier Snowmelt

Abstract In the Arctic, earlier snowmelt and longer growing seasons due to warming have been hypothesized to increase vegetation productivity. Using the Normalized Difference Vegetation Index (NDVI) from both field and satellite measurements as an indicator of vegetation phenology and productivity, we monitored spatial and temporal patterns of vegetation growth for a coastal wet sedge tundra site near Barrow, Alaska over three growing seasons (2000–2002). Contrary to expectation, earlier snowmelt did not lead to increased productivity. Instead, productivity was associated primarily with precipitation and soil moisture, and secondarily with growing degree days, which, during this period, led to reduced growth in years with earlier snowmelt. Additional moisture effects on productivity and species distribution, operating over a longer time scale, were evident in spatial NDVI patterns associated with microtopography. Lower, wetter regions dominated by graminoids were more productive than higher, drier locations having a higher percentage of lichens and mosses, despite the earlier snowmelt at the more elevated sites. These results call into question the oft-stated hypothesis that earlier arctic growing seasons will lead to greater vegetation productivity. Rather, they agree with an emerging body of evidence from recent field studies indicating that early-season, local environmental conditions, notably moisture and temperature, are primary factors determining arctic vegetation productivity. For this coastal arctic site, early growing season conditions are strongly influenced by microtopography, hydrology, and regional sea ice dynamics, and may not be easily predicted from snowmelt date or seasonal average air temperatures alone. Our comparison of field to satellite NDVI also highlights the value of in-situ monitoring of actual vegetation responses using field optical sampling to obtain detailed information on surface conditions not possible from satellite observations alone.

[1]  Harold A. Mooney,et al.  Response of Plants to Multiple Stresses , 1993 .

[2]  Steven F. Oberbauer,et al.  Remote sensing of tundra gross ecosystem productivity and light use efficiency under varying temperature and moisture conditions , 2010 .

[3]  Douglas A. Stow,et al.  Daily MODIS products for analyzing early season vegetation dynamics across the North Slope of Alaska , 2010 .

[4]  Ranga B. Myneni,et al.  Remote sensing of vegetation and land-cover change in Arctic Tundra Ecosystems , 2004 .

[5]  M. Sturm,et al.  Climate change: Increasing shrub abundance in the Arctic , 2001, Nature.

[6]  T. Wilbanks,et al.  Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change , 2007 .

[7]  Damiano Gianelle,et al.  SpecNet revisited: bridging flux and remote sensing communities , 2010 .

[8]  Christopher B. Field,et al.  RESPONSES OF TERRESTRIAL ECOSYSTEMS TO THE CHANGING ATMOSPHERE: A Resource-Based Approach*'** , 1992 .

[9]  Stefano Schiavon,et al.  Climate Change 2007: The Physical Science Basis. , 2007 .

[10]  C. Tweedie,et al.  High spatial resolution decade-time scale land cover change at multiple locations in the Beringian Arctic (1948–2000s) , 2012 .

[11]  H. L. Miller,et al.  Climate Change 2007: The Physical Science Basis , 2007 .

[12]  John A. Gamon,et al.  Tundra carbon balance under varying temperature and moisture regimes , 2010 .

[13]  S. Goswami,et al.  Monitoring Ecosystem Dynamics In An Arctic Tundra Ecosystem Using Hyperspectral Reflectance And A Robotic Tram System , 2011 .

[14]  Craig E. Tweedie,et al.  Surface hydrology of an arctic ecosystem: Multiscale analysis of a flooding and draining experiment using spectral reflectance , 2011 .

[15]  S. Goetz,et al.  Satellite-observed photosynthetic trends across boreal North America associated with climate and fire disturbance. , 2005, Proceedings of the National Academy of Sciences of the United States of America.

[16]  M. Schildhauer,et al.  Spectral Network (SpecNet)—What is it and why do we need it? , 2006 .

[17]  Rommel C. Zulueta,et al.  Effects of climate variability on carbon sequestration among adjacent wet sedge tundra and moist tussock tundra ecosystems , 2006 .

[18]  A. Hope.  Response of the normalized difference vegetation index to varying cloud conditions in Arctic tundra environments , 1999 .

[19]  John A. Gamon,et al.  A mobile tram system for systematic sampling of ecosystem optical properties , 2006 .

[20]  J. Silvola.  Combined effects of varying water content and CO2 concentration on photosynthesis in Spagnum fuscum , 1990 .

[21]  Robert D. Hollister,et al.  Estimated change in tundra ecosystem function near Barrow, Alaska between 1972 and 2010 , 2012 .

[22]  Allen Hope,et al.  Spatial distribution of near surface soil moisture and its relationship to microtopography in the Alaskan Arctic coastal plain , 2005 .

[23]  M. Torre Jorgenson,et al.  Abrupt increase in permafrost degradation in Arctic Alaska , 2006 .

[24]  Peter M. Lafleur,et al.  Does earlier snowmelt lead to greater CO2 sequestration in two low Arctic tundra ecosystems? , 2011 .

[25]  Douglas Stow,et al.  The relationship between tussock tundra spectral reflectance properties and biomass and vegetation composition , 1993 .

[26]  N. Bond,et al.  Recent Temperature Changes in the Western Arctic during Spring , 2002 .

[27]  F. Chapin,et al.  Evidence and Implications of Recent Climate Change in Northern Alaska and Other Arctic Regions , 2004 .

[28]  H. Soegaard,et al.  Temperature and snow-melt controls on interannual variability in carbon exchange in the high Arctic , 2007 .

[29]  J. Waddington,et al.  Moisture controls on Sphagnum growth and CO2 exchange on a cutover bog , 2003 .

[30]  F. Chapin,et al.  Role of Land-Surface Changes in Arctic Summer Warming , 2005, Science.

[31]  Arctic Monitoring,et al.  Impacts of a warming Arctic : Arctic Climate Impact Assessment , 2004 .

[32]  Peter M. Lafleur,et al.  Vegetation Community, Foliar Nitrogen, and Temperature Effects on Tundra CO2 Exchange across a Soil Moisture Gradient , 2011 .

[33]  J. Gamon,et al.  Microtopographic patterns in an arctic baydjarakh field: do fine-grain patterns enforce landscape stability? , 2012 .

[34]  L. D. Hinzman,et al.  Disappearing Arctic Lakes , 2005, Science.

[35]  Petya K. E. Campbell,et al.  Arctic Tundra Vegetation Functional Types Based on Photosynthetic Physiology and Optical Properties , 2013, IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing.

[36]  Steven B. Young,et al.  An Arctic Ecosystem. The Coastal Tundra at Barrow, Alaska. Jerry Brown , Philip C. Miller , Larry L. Tieszen , Fred L. BunnellTundra Ecosystems: A Comparative Analysis. L. C. Bliss , O. W. Heal , J. J. Moore , 1982 .

[37]  D. Douglas,et al.  Correlated declines in Pacific arctic snow and sea ice cover , 2005 .

[38]  C. Tucker,et al.  Increased plant growth in the northern high latitudes from 1981 to 1991 , 1997, Nature.

[39]  Walter C. Oechel,et al.  Recent change of Arctic tundra ecosystems from a net carbon dioxide sink to a source , 1993, Nature.

[40]  Robert S. Stone,et al.  Earlier spring snowmelt in northern Alaska as an indicator of climate change , 2002 .

[41]  R. Stone.  Variations in western Arctic temperatures in response to cloud radiative and synoptic‐scale influences , 1997 .

[42]  W. Gold,et al.  The patterning of plant communities and edaphic factors along a high arctic coastline: implications for succession , 1994 .

[43]  J. Berry,et al.  Photosynthetic Response and Adaptation to Temperature in Higher Plants , 1980 .

[44]  F. Stuart Chapin,et al.  Responses of Arctic Tundra to Experimental and Observed Changes in Climate , 1995 .

[45]  Steven F. Oberbauer,et al.  TUNDRA CO2 FLUXES IN RESPONSE TO EXPERIMENTAL WARMING ACROSS LATITUDINAL AND MOISTURE GRADIENTS , 2007 .

[46]  Harold A. Mooney,et al.  Responses of Plants to Multiple Stresses , 1993 .

[47]  J. Svoboda,et al.  Polar deserts, their plant cover and plant production in the Canadian High Arctic , 1984 .

[48]  C. Tucker,et al.  Circumpolar Arctic Tundra Vegetation Change Is Linked to Sea Ice Decline , 2010 .

[49]  S. Hagemann,et al.  Vulnerability of Permafrost Carbon to Climate Change: Implications for the Global Carbon Cycle , 2008 .

[50]  David L. Verbyla,et al.  Carbon loss from an unprecedented Arctic tundra wildfire , 2011, Nature.

[51]  F. Chapin,et al.  Ecosystem carbon storage in arctic tundra reduced by long-term nutrient fertilization , 2004, Nature.

[52]  F. Stuart Chapin,et al.  Species composition interacts with fertilizer to control long-term change in tundra productivity , 2001 .

[53]  Torsten Sachs,et al.  Global climate change and its impacts on the terrestrial Arctic carbon cycle with special regards to ecosystem components and the greenhouse‐gas balance , 2010 .