Does NDVI reflect variation in the structural attributes associated with increasing shrub dominance in arctic tundra?

This study explores relationships between the normalized difference vegetation index (NDVI) and structural characteristics associated with deciduous shrub dominance in arctic tundra. Our structural measures of shrub dominance are stature, branch abundance, aerial per cent woody stem cover (deciduous and evergreen species), and per cent deciduous shrub canopy cover. All measurements were taken across a suite of transects that together represent a gradient of deciduous shrub height. The transects include tussock tundra shrub and riparian shrub tundra communities located in the northern foothills of the Brooks Range, in northern Alaska. Plot-level NDVI measurements were made in 2010 during the snow-free period prior to deciduous shrub leaf-out (early June, NDVIpre − leaf), at the point in the growing season when canopy NDVI has reached half of its maximum growing season value (mid-June, NDVIdemi − leaf) and during the period of maximum leaf-out (late July, NDVIpeak − leaf). We found that: (1) NDVIpre − leaf is best suited to capturing variation in the per cent woody stem cover, maximum shrub height, and branch abundance, particularly between 10 and 50 cm height in the canopy; (2) NDVIpeak − leaf is best suited to capturing variation in deciduous canopy cover; and (3) NDVIdemi − leaf does not capture variability in any of our measures of shrub dominance. These findings suggest that in situ NDVI measurements made prior to deciduous canopy leaf-out could be used to identify small differences in maximum shrub height, woody stem cover, and branch abundance (particularly between 10 and 50 cm height in the canopy). Because shrubs are increasing in size and regional extent in several regions of the Arctic, investigation into spectrally based tools for monitoring these changes are worthwhile as they provide a first step towards development of remotely sensed techniques for quantifying associated changes in regional carbon cycling, albedo, radiative energy balance, and wildlife habitat.

[1]  S. Goetz,et al.  Shrub Cover on the North Slope of Alaska: a circa 2000 Baseline Map , 2011 .

[2]  S. Goetz,et al.  Tundra vegetation effects on pan-Arctic albedo , 2011 .

[3]  L. Vierling,et al.  Spinning a laser web: predicting spider distributions using LiDAR. , 2011, Ecological applications : a publication of the Ecological Society of America.

[4]  David J. Selkowitz,et al.  A comparison of multi-spectral, multi-angular, and multi-temporal remote sensing datasets for fractional shrub canopy mapping in Arctic Alaska , 2010 .

[5]  S. Goetz,et al.  Lidar remote sensing variables predict breeding habitat of a Neotropical migrant bird. , 2010, Ecology.

[6]  B. Forbes,et al.  Russian Arctic warming and ‘greening’ are closely tracked by tundra shrub willows , 2010 .

[7]  J. Cornelissen,et al.  Ecosystem feedbacks and cascade processes: understanding their role in the responses of Arctic and alpine ecosystems to environmental change , 2009 .

[8]  F. Hu,et al.  Frequent Fires in Ancient Shrub Tundra: Implications of Paleorecords for Arctic Environmental Change , 2008, PloS one.

[9]  Roberta E. Martin,et al.  Multi-trophic invasion resistance in Hawaii: bioacoustics, field surveys, and airborne remote sensing. , 2007, Ecological applications : a publication of the Ecological Society of America.

[10]  S. Goetz,et al.  Northern high‐latitude ecosystems respond to climate change , 2007 .

[11]  Steven F. Oberbauer,et al.  Relating NDVI to ecosystem CO2 exchange patterns in response to season length and soil warming manipulations in arctic Alaska , 2007 .

[12]  S. Ustin,et al.  Estimation of shrub height for fuel-type mapping combining airborne LiDAR and simultaneous color infrared ortho imaging , 2007 .

[13]  G. R. Shaver,et al.  What is the relationship between changes in canopy leaf area and changes in photosynthetic CO2 flux in arctic ecosystems? , 2007 .

[14]  Roberta E. Martin,et al.  Carnegie Airborne Observatory: in-flight fusion of hyperspectral imaging and waveform light detection and ranging for three-dimensional studies of ecosystems , 2007 .

[15]  J. Welker,et al.  Modeling the effect of photosynthetic vegetation properties on the NDVI--LAI relationship. , 2006, Ecology.

[16]  Donald A. Walker,et al.  NDVI patterns and phytomass distribution in the circumpolar Arctic , 2006 .

[17]  M. Sturm,et al.  The evidence for shrub expansion in Northern Alaska and the Pan‐Arctic , 2006 .

[18]  Steven F. Oberbauer,et al.  Plant community responses to experimental warming across the tundra biome , 2006, Proceedings of the National Academy of Sciences of the United States of America.

[19]  Howard E. Epstein,et al.  Spatial heterogeneity of tundra vegetation response to recent temperature changes , 2006 .

[20]  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.

[21]  G. Liston,et al.  Changing snow and shrub conditions affect albedo with global implications , 2005 .

[22]  J. Schimel,et al.  Nitrogen Cycling and the Spread of Shrubs Control Changes in the Carbon Balance of Arctic Tundra Ecosystems , 2005 .

[23]  M. Bret-Harte,et al.  Vegetation responses in Alaskan arctic tundra after 8 years of a summer warming and winter snow manipulation experiment , 2005 .

[24]  Marc Stieglitz,et al.  Inter-annual variability of NDVI in response to long-term warming and fertilization in wet sedge and tussock tundra , 2005, Oecologia.

[25]  D. Walker,et al.  Spatial and Temporal Heterogeneity of Vegetation Properties among Four Tundra Plant Communities at Ivotuk, Alaska, U.S.A , 2005 .

[26]  Barrow Atqasuk Oumalik Ivotuk West Dock Deadhorse Frankli Sagwon.  Spatial heterogeneity of tundra vegetation response to recent temperature changes , 2005 .

[27]  J. Wingfield,et al.  Arctic spring: The arrival biology of migrant birds , 2004 .

[28]  Global change: Carbon conundrum on the tundra , 2004, Nature.

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

[30]  F. Stuart Chapin,et al.  Detecting changes in arctic tundra plant communities in response to warming over decadal time scales , 2004 .

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

[32]  S. Jonasson.  Plant communities and species distribution of low alpine Betula nana heaths in Northernmost Sweden , 2004, Vegetatio.

[33]  M. V. van Wijk,et al.  Interannual variability of plant phenology in tussock tundra: modelling interactions of plant productivity, plant phenology, snowmelt and soil thaw , 2003 .

[34]  J. Gamon,et al.  Response of NDVI, biomass, and ecosystem gas exchange to long-term warming and fertilization in wet sedge tundra , 2003, Oecologia.

[35]  W. Gould,et al.  Phytomass, LAI, and NDVI in northern Alaska: Relationships to summer warmth, soil pH, plant functional types, and extrapolation to the circumpolar Arctic , 2003 .

[36]  F. Stuart Chapin,et al.  Primary and secondary stem growth in arctic shrubs: implications for community response to environmental change , 2002 .

[37]  C. Dormann,et al.  Climate change in the Arctic: using plant functional types in a meta‐analysis of field experiments , 2002 .

[38]  W. Cohen,et al.  Lidar Remote Sensing for Ecosystem Studies , 2002 .

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

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

[41]  J. Johnstone,et al.  DEVELOPMENTAL PLASTICITY ALLOWS BETULA NANA TO DOMINATE TUNDRA SUBJECTED TO AN ALTERED ENVIRONMENT , 2001 .

[42]  F. Chapin,et al.  Interactions of shrubs and snow in arctic tundra: measurements and models , 2001 .

[43]  E. Rastetter,et al.  Vegetation characteristics and primary productivity along an arctic transect: implications for scaling‐up , 1999 .

[44]  Donald A. Walker,et al.  Landsat MSS-derived land-cover map of northern Alaska: Extrapolation methods and a comparison with photo-interpreted and AVHRR-derived maps , 1999 .

[45]  F. Chapin,et al.  An experimental test of limits to tree establishment in Arctic tundra , 1998 .

[46]  G. Asner.  Biophysical and Biochemical Sources of Variability in Canopy Reflectance , 1998 .

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

[48]  Lee A. Vierling,et al.  Differences in arctic tundra vegetation type and phenology as seen using bidirectional radiometry in the early growing season , 1997 .

[49]  F. Chapin,et al.  Physiological and Growth Responses of Arctic Plants to a Field Experiment Simulating Climatic Change , 1996 .

[50]  S. Hobbie.  Temperature and plant species control over litter decomposition in Alaskan tundra , 1996 .

[51]  F. Chapin,et al.  Long-term responses to factorial, NPK fertilizer treatment by Alaskan wet and moist tundra sedge species , 1995 .

[52]  F. Hu,et al.  Postglacial Vegetation and Climate Change in the Northern Bristol Bay Region, Southwestern Alaska , 1995, Quaternary Research.

[53]  N. Auerbach,et al.  Biomass and leaf-area index maps derived from SPOT images for Toolik Lake and Imnavait Creek areas, Alaska , 1995, Polar Record.

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

[55]  J. Schaefer,et al.  Scale-dependent Correlations of Arctic Vegetation and Snow Cover , 1995 .

[56]  F. Hu,et al.  Arctic Tundra Biodiversity: A Temporal Perspective from Late Quaternary Pollen Records , 1995 .

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

[58]  James F. Reynolds,et al.  Arctic ecosystems in a changing climate : an ecophysiological perspective , 1993 .

[59]  N. Matveyeva,et al.  4 – Circumpolar Arctic Vegetation , 1992 .

[60]  Douglas L. Kane,et al.  Snow hydrology of a headwater Arctic basin: 1. Physical measurements and process studies , 1991 .

[61]  L. Hinzman,et al.  Snow Hydrology of a Headwater Arctic Basin 2 , 1991 .

[62]  G. O. Batzli,et al.  The influence of high quality food on habitat use by arctic microtine rodents , 1991 .

[63]  Donald A. Walker,et al.  Spatial interrelationships between terrain, snow distribution and vegetation patterns at an arctic foothills site in Alaska , 1989 .

[64]  Ghassem R. Asrar,et al.  Leaf-area estimates from spectral measurements over various planting dates of wheat , 1985 .

[65]  J. A. Schell,et al.  Monitoring vegetation systems in the great plains with ERTS , 1973 .

[66]  R. Macarthur,et al.  On Bird Species Diversity , 1961 .