Advertisement

Ecosystems

, Volume 17, Issue 7, pp 1151–1168 | Cite as

Warming-Induced Shrub Expansion and Lichen Decline in the Western Canadian Arctic

  • Robert H. FraserEmail author
  • Trevor C. Lantz
  • Ian Olthof
  • Steven V. Kokelj
  • Richard A. Sims
Article

Abstract

Strong evidence for a pan-Arctic expansion of upright shrubs comes from analysis of satellite imagery, historical photographs, vegetation plots, and growth rings. However, there are still uncertainties related to local-scale patterns of shrub growth, resulting interactions among vegetation functional groups, and the relative roles of disturbance and climate as drivers of observed change. Here, we present evidence that widespread and rapid shrub expansion and lichen declines over a 15,000 km2 area of the western Canadian Arctic have been driven by regional increases in temperature. Using 30 m resolution Landsat satellite imagery and high resolution repeat color-infrared aerial photographs, we show that 85% of the land surface has a positive 1985–2011 trend (P < 0.05) in NDVI, making this one of the most intensely greening regions in the Arctic. Strong positive trends (>0.03 NDVI/decade) occurred consistently across all landscape positions and most vegetation types. Comparison of 208, 1:2,000 scale vertical air photo pairs from 1980 and 2013 clearly shows that this greening was driven by increased canopy cover of erect dwarf and tall shrubs, with declines in terricolous lichen cover. Disturbances caused by wildfires, exploratory gas wells, and drained lakes all produced strong, yet localized increases in NDVI due to shrub growth. Our analysis also shows that a 4°C winter temperature increase over the past 30 years, leading to warmer soils and enhanced nutrient mineralization provides the best explanation for observed vegetation change. These observations thus provide early corroboration for modeling studies predicting large-scale vegetation shifts in low-Arctic ecosystems from climate change.

Keywords

climate change landsat lichen remote sensing satellite air photos shrubs 

Notes

Acknowledgments

We thank Ken Baldwin from the Canadian Forest Service for help in locating and shipping the 1980 CIR film canisters, Alice Deschamps and Marilee Pregitzer from CCMEO for assisting with film scanning and photo processing, and Alex Brooker from University of Ottawa for processing the Landsat image scenes. Wenjun Chen and Darren Pouliot from CCMEO, and Jan Adamczewski from Government of NWT offered helpful comments to improve the paper. The Polar Continental Shelf Program of Natural Resources Canada provided helicopter time from Great Slave Helicopters to acquire the 2013 photos and conduct ground surveys. Funding for this work was provided by the NWT Cumulative Impacts Monitoring Program under the project “A Multi-scale Assessment of Cumulative Impacts in the Northern Mackenzie Basin” led by Claire Marchildon of Aboriginal Affairs and Northern Development Canada, and a Natural Sciences and Engineering Research Council Discovery Grant to Trevor Lantz. For field assistance and logistical support we thank: Richard Binder, Jeff Moore, Emanuel Adam, Douglas Panaktalok, Yu Zhang, the Aurora Research Institute, and the Inuvialuit Joint Secretariat.

Supplementary material

10021_2014_9783_MOESM1_ESM.docx (16.8 mb)
Supplementary material 1 (DOCX 17232 kb)

References

  1. ACIA. 2004. Impacts of a warming Arctic: Arctic climate impact assessment. Cambridge: Cambridge University Press.Google Scholar
  2. Beck PSA, Goetz SJ. 2011. Satellite observations of high northern latitude vegetation productivity changes between 1982 and 2008: ecological variability and regional differences. Environ Res Lett 6:045501.CrossRefGoogle Scholar
  3. Beers TW, Dress PE, Wensel LC. 1966. Aspect transformation in site productivity research. J Forest 64:691–2.Google Scholar
  4. Beven KJ, Kirkby MJ. 1979. A physically based, variable contributing area model of basin hydrology. Hydrol Sci Bull 24:43–69.CrossRefGoogle Scholar
  5. Bhatt US, Walker DA, Raynolds MK, Comiso JC, Epstein HE, Jia GS, Gens R, Pinzon JE, Tucker CJ, Tweedie CE, Webber PJ. 2010. Circumpolar Arctic tundra vegetation change is linked to sea ice decline. Earth Interact 14:1–20.CrossRefGoogle Scholar
  6. Blok D, Heijmans MMPD, Schaepman-Strub G, Kononov AV, Maximov TC, Berendse F. 2010. Shrub expansion may reduce summer permafrost thaw in Siberian tundra. Glob Change Biol 16:1296–305.CrossRefGoogle Scholar
  7. Blok D, Sass-Klaassen U, Schaepman-Strub G, Heijmans MMPD, Sauren P, Berendse F. 2011a. What are the main climate drivers for shrub growth in Northeastern Siberian tundra? Biogeosciences 8:1169–79.CrossRefGoogle Scholar
  8. Blok D, Schaepman-Strub G, Bartholomeus H, Heijmans MMPD, Maximov TC, Berendse F. 2011b. The response of Arctic vegetation to the summer climate: relation between shrub cover, NDVI, surface albedo and temperature. Environ Res Lett 6:035502.CrossRefGoogle Scholar
  9. Bret-Harte MS, Shaver GR, Zoerner JP, Johnstone JF, Wagner JL, Chavez AS, Gunkelman RF, Lippert SC, Laundre JA. 2001. Developmental plasticity allows Betula nana to dominate tundra subjected to an altered environment. Ecology 82:18–32.CrossRefGoogle Scholar
  10. Burn CR, Kokelj SV. 2009. The environment and permafrost of the Mackenzie delta area. Permafr Periglac Process 20:83–105.CrossRefGoogle Scholar
  11. Chapin FS. 1983. Direct and indirect effects of temperature on arctic plants. Polar Biol 2:47–52.CrossRefGoogle Scholar
  12. Chapin FS, Shaver GR, Giblin AE, Nadelhoffer KJ, Laundre JA. 1995. Responses of Arctic tundra to experimental and observed changes in climate. Ecology 76:694–711.CrossRefGoogle Scholar
  13. Chapin FS, Sturm M, Serreze MC, McFadden JP, Key JR, Lloyd AH, McGuire AD, Rupp TS, Lynch AH, Schimel JP, Beringer J, Chapman WL, Epstein HE, Euskirchen ES, Hinzman LD, Jia G, Ping CL, Tape KD, Thompson CDC, Walker DA, Welker JM. 2005. Role of land-surface changes in Arctic summer warming. Science 310:657–60.PubMedCrossRefGoogle Scholar
  14. Chen W, Chen W, Li J, Zhang Y, Fraser R, Olthof I, Leblanc SG, Chen Z. 2012. Mapping aboveground and foliage biomass over the Porcupine Caribou habitat in Northern Yukon and Alaska using Landsat and JERS-1/SAR data. In: Dr. Lola Fatoyinbo, editor. Remote sensing of biomass—principles and applications. Novi Sad: InTech. ISBN: 978-953-51-0313-4.Google Scholar
  15. Cody WJ. 1963. Reindeer range survey 1957 and 1963. Ottawa, ON: Plant Research Institute, Canada Department of Agriculture, Central Experimental Farm.Google Scholar
  16. Cornelissen JHC, Callaghan TV, Alatalo JM, Michelsen A, Graglia E, Hartley AE, Hik DS, Hobbie SE, Press MC, Robinson CH, Henry GHR, Shaver GR, Phoenix GK, Gwynn Jones D, Jonasson S, Chapin FS, Molau U, Neill C, Lee JA, Melillo JM, Sveinbjörnsson B, Aerts R. 2001. Global change and arctic ecosystems: is lichen decline a function of increases in vascular plant biomass? J Ecol 89:984–94.CrossRefGoogle Scholar
  17. Corns IGW. 1974. Arctic plant communities east of Mackenzie-Delta. Can J Bot 52:1731–45.CrossRefGoogle Scholar
  18. Ecosystem Classification Group. 2012. Ecological regions of the Northwest Territories—Southern Arctic. Yellowknife, NT: Department of Environment and Natural Resources, Government of the Northwest Territories. x + 170 pp. + insert map.Google Scholar
  19. Elmendorf SC, Henry GHR, Hollister RD, Bjork RG, Bjorkman AD, Callaghan TV, Collier LS, Cooper EJ, Cornelissen JHC, Day TA, Fosaa AM, Gould WA, Gretarsdottir J, Harte J, Hermanutz L, Hik DS, Hofgaard A, Jarrad F, Jonsdottir IS, Keuper F, Klanderud K, Klein JA, Koh S, Kudo G, Lang SI, Loewen V, May JL, Mercado J, Michelsen A, Molau U, Myers-Smith IH, Oberbauer SF, Pieper S, Post E, Rixen C, Robinson CH, Schmidt NM, Shaver GR, Stenstrom A, Tolvanen A, Totland O, Troxler T, Wahren CH, Webber PJ, Welker JM, Wookey PA. 2012a. Global assessment of experimental climate warming on tundra vegetation: heterogeneity over space and time. Ecol Lett 15:164–75.PubMedCrossRefGoogle Scholar
  20. Elmendorf SC, Henry GHR, Hollister RD, Björk RG, Boulanger-Lapointe N, Cooper EJ, Cornelissen JHC, Day TA, Dorrepaal E, Elumeeva TG, Gill M, Gould WA, Harte J, Hik DS, Hofgaard A, Johnson DR, Johnstone JF, Jónsdóttir IS, Jorgenson JC, Klanderud K, Klein JA, Koh S, Kudo G, Lara M, Lévesque E, Magnússon B, May JL, Mercado-Dı´az JA, Michelsen A, Molau U, Myers-Smith IH, Oberbauer SF, Onipchenko VG, Rixen C, Martin Schmidt N, Shaver GR, Spasojevic MJ, Þórhallsdóttir ÞE, Tolvanen A, Troxler T, Tweedie CE, Villareal S, Wahren C-H, Walker X, Webber PJ, Welker JM, Wipf S. 2012b. Plot-scale evidence of tundra vegetation change and links to recent summer warming. Nat Clim Change 2:453–457.Google Scholar
  21. Environment Canada. 2012. National climate data and information archive. Ottawa: Environment Canada. http://climate.weatheroffice.ec.gc.ca/climateData/canada_e.html. Accessed 16 June 2014.
  22. Epstein HE, Beringer J, Gould WA, Lloyd AH, Thompson CD, Chapin FS, Michaelson GJ, Ping CL, Rupp TS, Walker DA. 2004a. The nature of spatial transitions in the Arctic. J Biogeogr 31:1917–33.CrossRefGoogle Scholar
  23. Epstein HE, Calef MP, Walker MD, Chapin FS, Starfield AM. 2004b. Detecting changes in Arctic tundra plant communities in response to warming over decadal time scales. Glob Change Biol 10:1325–34.CrossRefGoogle Scholar
  24. Epstein HE, Walker DA, Bhatt US, Bieniek P, Comiso J, Pinzon J, Raynolds MK, Tucker CJ, Jia GJ, Zeng H, Myers-Smith IH, Forbes BC, Blok D, Loranty MM, Beck PSA, Goetz SJ, Callaghan TV, Henry GHR, Tweedie CE, Webber PJ, Rocha AV, Shaver GR, Welker JM, Carlson ML. 2012a. Vegetation [in Arctic Report Card 2012]. http://www.arctic.noaa.gov/report12/. Accessed 16 June 2014.
  25. Epstein HE, Raynolds MK, Walker DA, Bhatt US, Tucker CJ, Pinzon JE. 2012b. Dynamics of aboveground phytomass of the circumpolar Arctic tundra during the past three decades. Environ Res Lett 7:015506.CrossRefGoogle Scholar
  26. Epstein HE, Myers-Smith I, Walker DA. 2013. Recent dynamics of Arctic and sub-Arctic vegetation. Environ Res Lett 8:015040.CrossRefGoogle Scholar
  27. Euskirchen ES, McGuire AD, Chapin FS, Yi S, Thompson CC. 2009. Changes in vegetation in northern Alaska under scenarios of climate change, 2003–2100: implications for climate feedbacks. Ecol Appl 19:1022–43.PubMedCrossRefGoogle Scholar
  28. Forbes BC, Fauria MM, Zetterberg P. 2010. Russian Arctic warming and ‘greening’ are closely tracked by tundra shrub willows. Glob Change Biol 16:1542–54.CrossRefGoogle Scholar
  29. Fraser RH, Olthof I, Carriere M, Deschamps A, Pouliot D. 2011. Detecting long-term changes to vegetation in northern Canada using the Landsat satellite image archive. Environ Res Lett 6:045502.CrossRefGoogle Scholar
  30. Frost GV, Epstein HE, Walker DA, Matyshak G, Ermokhina K. 2013. Patterned-ground facilitates shrub expansion in Low Arctic tundra. Environ Res Lett 8:015035.CrossRefGoogle Scholar
  31. GNWT. 2011. Environmental impact statement for construction of the Inuvik to Tuktoyaktuk highway, NWT. Government of Northwest Territories EIRB File No. 02/10-05. http://www.dot.gov.nt.ca/_live/documents/content/EIS%20Inuvik%20to%20Tuk%20Highway%20low%20res.pdf. Accessed 16 June 2014.
  32. Goetz SJ, Bunn AG, Fiske GJ, Houghton RA. 2005. Satellite-observed photosynthetic trends across boreal North America associated with climate and fire disturbance. Proc Nat Acad Sci USA 102:13521–5.PubMedCrossRefPubMedCentralGoogle Scholar
  33. Higuera PE, Brubaker LB, Anderson PM, Brown TA, Kennedy AT, Hu FS. 2008. Frequent fires in ancient shrub tundra: implications of paleo-records for Arctic environmental change. PLoS ONE 3:e0001744.PubMedCrossRefGoogle Scholar
  34. Hope AS, Kimball JS, Stow DA. 1993. The relationship between tussock tundra spectral reflectance properties and biomass and vegetation composition. Int J Remote Sens 14:1861–74.CrossRefGoogle Scholar
  35. Jandt R, Joly K, Meyers CR, Racine C. 2008. Slow recovery of lichen on burned caribou winter range in Alaska tundra: potential influences of climate warming and other disturbance factors. Arct Antarct Alp Res 40:89–95.CrossRefGoogle Scholar
  36. Johnstone JF, Kokelj SV. 2008. Environmental conditions and vegetation recovery at abandoned-drilling mud sumps in the Mackenzie Delta region, NWT, Canada. Arctic 61:199–211.Google Scholar
  37. Joly K, Cole MJ, Jandt RR. 2007a. Diets of overwintering caribou, Rangifer tarandus, track decadal changes in Arctic tundra vegetation. Can Field Nat 121:379–83.Google Scholar
  38. Joly K, Jandt RR, Meyers CR, Cole MJ. 2007b. Changes in vegetative cover on Western Arctic Herd winter range from 1981 to 2005; potential effects of grazing and climate change. Rangifer 17:199–206.CrossRefGoogle Scholar
  39. Joly K, Jandt RR, Klein DR. 2009. Decrease of lichens in Arctic ecosystems: the role of wildfire, caribou, reindeer, competition and climate in north-western Alaska. Polar Res 28:433–42.CrossRefGoogle Scholar
  40. Jorgenson MT, Shur YL, Pullman ER. 2006. Abrupt increase in permafrost degradation in Arctic Alaska. Geophys Res Lett 33:L02503.CrossRefGoogle Scholar
  41. Kemper JT, Macdonald SE. 2009. Directional change in upland tundra plant communities 20–30 years after seismic exploration in the Canadian low-Arctic. J Veg Sci 20:557–67.CrossRefGoogle Scholar
  42. Kendall M. 1975. Rank correlation methods. London: Charles Griffin.Google Scholar
  43. Klein DR, Shulski M. 2011. The role of lichens, reindeer, and climate in ecosystem change on a Bering Sea island. Arctic 64:353–61.Google Scholar
  44. Kokelj SV, Riseborough D, Coutts R, Kanigan JCN. 2010. Permafrost and terrain conditions at northern drilling-mud sumps: impacts of vegetation and climate change and the management implications. Cold Reg Sci Technol 64:46–56.CrossRefGoogle Scholar
  45. Kumar A, Perlwitz J, Eischeid J, Quan X, Xu T, Zhang T, Hoerling M, Jha B, Wang W. 2010. Contribution of sea ice loss to Arctic amplification. Geophys Res Lett 37:L21701.Google Scholar
  46. Lantz TC, Kokelj SV. 2008. Increasing rates of retrogressive thaw slump activity in the Mackenzie Delta region, N.W.T., Canada. Geophys Res Lett 35:L06502. doi: 10.1029/2007GL032433.CrossRefGoogle Scholar
  47. Lantz TC, Kokelj SV, Gergel SE, Henry GHR. 2009. Relative impacts of disturbance and temperature: persistent changes in microenvironment and vegetation in retrogressive thaw slumps. Glob Change Biol 15:1664–75.CrossRefGoogle Scholar
  48. Lantz TC, Gergel SE, Henry GHR. 2010. Response of green alder (Alnus viridis subsp. fruticosa) patch dynamics and plant community composition to fire and regional temperature in north-western Canada. J Biogeogr 37:1597–610.Google Scholar
  49. Lantz TC, Marsh P, Kokelj SV. 2013. Recent shrub proliferation in the Mackenzie Delta uplands and microclimatic implications. Ecosystems 16:47–59.CrossRefGoogle Scholar
  50. Macias-Fauria M, Forbes BC, Zetterberg P, Kumpula T. 2012. Eurasian Arctic greening reveals teleconnections and the potential for structurally novel ecosystems. Nat Clim Change 2:613–18.CrossRefGoogle Scholar
  51. Mackay J, Burn C. 2011. A century (1910–2008) of change in a collapsing pingo, Parry Peninsula, Western Arctic Coast, Canada. Permafr Periglac Process 22:266–72. doi: 10.1002/ppp.723.Google Scholar
  52. Manseau M, Huot J, Crete M. 1996. Effects of summer grazing by caribou on composition and productivity of vegetation: community and landscape level. J Ecol 84:503–13.CrossRefGoogle Scholar
  53. Marsh P, Russell M, Pohl S, Haywood H, Onclin C. 2009. Changes in thaw lake drainage in the Western Canadian Arctic from 1950 to 2000. Hydrol Process 23:145–58.CrossRefGoogle Scholar
  54. McManus KM, Morton DC, Masek JG, Wang D, Sexton JO, Nagol JR, Ropars P, Boudreau S. 2012. Satellite-based evidence for shrub and graminoid tundra expansion in northern Quebec from 1986 to 2010. Glob Change Biol 18:2313–23.CrossRefGoogle Scholar
  55. Myers-Smith IH, Hik DS, Kennedy C, Cooley D, Johnstone JF, Kenney AJ, Krebs CJ. 2011a. Expansion of canopy-forming willows over the twentieth century on Herschel Island, Yukon Territory, Canada. Ambio 40:610–23.PubMedCrossRefPubMedCentralGoogle Scholar
  56. Myers-Smith IH, Forbes BC, Wilmking M, Hallinger M, Lantz T, Blok D, Tape KD, Macias-Fauria M, Sass-Klaassen U, Lévesque E, Boudreau S, Ropars P, Hermanutz L, Trant A, Collier LS, Weijers S, Rozema J, Rayback SA, Schmidt NM, Schaepman-Strub G, Wipf S, Rixen C, Ménard CB, Venn S, Goetz S, Andreu-Hayles L, Elmendorf S, Ravolainen V, Welker J, Grogan P, Epstein HE, Hik DS. 2011b. Shrub expansion in tundra ecosystems: dynamics, impacts and research priorities. Environ Res Lett 6:045509.CrossRefGoogle Scholar
  57. Naito AT, Cairns DM. 2011. Relationships between Arctic shrub dynamics and topographically derived hydrologic characteristics. Environ Res Lett 6:045506.CrossRefGoogle Scholar
  58. Olofsson J, Oksanen L, Callaghan T, Hulme PE, Oksanen T, Suominen O. 2009. Herbivores inhibit climate-driven shrub expansion on the tundra. Glob Chang Biol 15:2681–93.CrossRefGoogle Scholar
  59. Olthof I, Latifovic R. 2007. Short-term response of Arctic vegetation NDVI to temperature anomalies. Int J Remote Sens 28:4823–40.CrossRefGoogle Scholar
  60. Olthof I, Pouliot D. 2008. Recent (1986–2006) vegetation-specific NDVI trends in Northern Canada from satellite data. Arctic 61:381–94.Google Scholar
  61. Palmer MJ, Burn CR, Kokelj SV. 2012. Factors influencing permafrost temperatures across tree line in the uplands east of the Mackenzie Delta, 2004–2010. Can J Earth Sci 49(8):877–94. doi: 10.1139/e2012-002.CrossRefGoogle Scholar
  62. Pearson RG, Phillips SJ, Loranty MM, Beck PSA, Damoulas T, Knight SJ, Goetz SJ. 2013. Shifts in Arctic vegetation and associated feedbacks under climate change. Nat Clim Change 3:673–7.CrossRefGoogle Scholar
  63. Pouliot D, Latifovic R, Olthof I. 2009. Trends in vegetation NDVI from 1 km AVHRR data over Canada for the period 1985–2006. Int J Remote Sens 30:149–68.CrossRefGoogle Scholar
  64. Racine C, Jandt R, Meyers C, Dennis J. 2004. Tundra fire and vegetation change along a hillslope on the Seward Peninsula, Alaska, USA. Arct Antarct Alp Res 36:1–10.CrossRefGoogle Scholar
  65. Rampton VN. 1988. Quaternary geology of the Tuktoyaktuk Coastlands, Northwest Territories. Memoir 423. Ottawa: Geological Survey of Canada, Energy Mines and Resources Canada.Google Scholar
  66. Raynolds MK, Walker DA, Epstein HE, Pinzon JE, Tucker CJ. 2012. A new estimate of tundra-biome phytomass from trans-arctic field data and AVHRR NDVI. Remote Sens Lett 3:403–11.CrossRefGoogle Scholar
  67. Raynolds MK, Walker DA, Verbyla D, Munger CA. 2013. Patterns of change within a tundra landscape: 22-year Landsat NDVI trends in an area of the northern foothills of the Brooks Range, Alaska. Arct Antarc Alp Res 45:249–60.CrossRefGoogle Scholar
  68. Riedel SM, Epstein HE, Walker DA. 2005. Biotic controls over spectral reflectance of Arctic tundra vegetation. Int J Remote Sens 26:2391–405.CrossRefGoogle Scholar
  69. Rocha AV, Loranty MM, Higuera PE, Mack MC, Hu FS, Jones BM, Breen AL, Rastetter EB, Goetz SJ, Shaver GR. 2012. The footprint of Alaskan tundra fires during the past half-century: implications for surface properties and radiative forcing. Environ Res Lett 7:044039.CrossRefGoogle Scholar
  70. Ropars P, Boudreau S. 2012. Shrub expansion at the forest–tundra ecotone: spatial heterogeneity linked to local topography. Environ Res Lett 7:015501.CrossRefGoogle Scholar
  71. Schneider CA, Rasband WS, Eliceiri KW. 2012. NIH Image to ImageJ: 25 years of image analysis. Nat Methods 9:671–5.PubMedCrossRefGoogle Scholar
  72. Screen JA, Simmonds I. 2010. The central role of diminishing sea ice in recent Arctic temperature amplification. Nature 464:1334–7.PubMedCrossRefGoogle Scholar
  73. Sims RA. 1983. Ground-truth and large-scale 70 mm aerial photographs in the study of reindeer winter rangeland, Tuktoyaktuk Peninsula area, NWT. PhD thesis, University of British Columbia.Google Scholar
  74. Smith SL, Burgess MM, Riseborough D, Nixon FM. 2005. Recent trends from Canadian permafrost thermal monitoring network sites. Permafr Periglac 16:19–30.CrossRefGoogle Scholar
  75. Sturm M, Schimel J, Michaelson G, Welker JM, Oberbauer SF, Liston GE, Fahnestock J, Romanovsky VE. 2005. Winter biological processes could help convert Arctic tundra to shrub land. Bioscience 55:17–26.CrossRefGoogle Scholar
  76. Tape K, Sturm M, Racine C. 2006. The evidence for shrub expansion in Northern Alaska and the Pan-Arctic. Glob Change Biol 12:686–702.CrossRefGoogle Scholar
  77. Tape KD, Hallinger M, Welker JM, Ruess RW. 2012. Landscape heterogeneity of shrub expansion in Arctic Alaska. Ecosystems 15:711–24.CrossRefGoogle Scholar
  78. Timoney KP, La Roi GH, Zoltai SC, Robinson AL. 1992. The high subarctic forest-tundra of Northwestern Canada: position, width, and vegetation gradients in relation to climate. Arctic 45:1–9.CrossRefGoogle Scholar
  79. Tremblay B, Lévesque E, Boudreau S. 2012. Recent expansion of erect shrubs in the low Arctic: evidence from Eastern Nunavik. Environ Res Lett 7:035501.CrossRefGoogle Scholar
  80. Tucker CJ. 1979. Red and photographic infrared linear combinations for monitoring vegetation. Rem Sens Environ 8:27–150.Google Scholar
  81. Vincent LA, Wang XL, Milewska EJ, Wan H, Yang F, Swail V. 2012. A second generation of homogenized Canadian monthly surface air temperature for climate trend analysis. J Geophys Res Atm 117:D18110.CrossRefGoogle Scholar
  82. Wahren C-HA, Walker MD, Bret-Harte MS. 2005. Vegetation responses in Alaskan Arctic tundra after 8 years of a summer warming and winter snow manipulation experiment. Glob Change Biol 11:537–52.CrossRefGoogle Scholar
  83. Walker DA. 1987. Height and growth rings of Salix lanata ssp. richardsonii along the coastal temperature gradient of northern Alaska. Can J Bot 65:988–93.Google Scholar
  84. Walker DA, Raynolds MK, Daniëls FJA, Einarsson E, Elvebakk A, Gould WA, Katenin AE, Kholod SS, Markon CJ, Melnikov ES, Moskalenko NG, Talbot SS, Yurtsev BA, Other Members of the CAVM Team. 2005. The circumpolar Arctic vegetation map. J Veg Sci 16:267–82.CrossRefGoogle Scholar
  85. Walker MD, Wahren CH, Hollister RD, Henry GHR, Ahlquist LE, Alatalo JM, Bret-Harte MS, Calef MP, Callaghan TV, Carroll AB, Epstein HE, Jonsdottir IS, Klein JA, Magnusson B, Molau U, Oberbauer SF, Rewa SP, Robinson CH, Shaver GR, Suding KN, Thompson CC, Tolvanen A, Totland O, Turner PL, Tweedie CE, Webber PJ, Wookey PA. 2006. Plant community responses to experimental warming across the tundra biome. Proc Natl Acad Sci USA 103:1342–6.PubMedCrossRefPubMedCentralGoogle Scholar
  86. Xu L, Myneni RB, Chapin FS, Callaghan TV, Pinzon JE, Tucker CJ, Zhu Z, Bi J, Ciais P, Tommervik H, Euskirchen ES, Forbes BC, Piao SL, Anderson BT, Ganguly S, Nemani RR, Goetz SJ, Beck PSA, Bunn AG, Cao C, Stroeve JC. 2013. Temperature and vegetation seasonality diminishment over northern lands. Nat Clim Change 3:581–6.Google Scholar
  87. Zamin TJ, Grogan P. 2013. Caribou exclusion during a population low increases deciduous and evergreen shrub species biomass and nitrogen pools in low Arctic tundra. J Ecol 101:671–83.CrossRefGoogle Scholar
  88. Zhu Z, Woodcock CE. 2012. Object-based cloud and cloud shadow detection in Landsat imagery. Rem Sens Environ 118:83–94.CrossRefGoogle Scholar

Copyright information

© UKCrown: Natural Resources Canada 2014

Authors and Affiliations

  • Robert H. Fraser
    • 1
    Email author
  • Trevor C. Lantz
    • 2
  • Ian Olthof
    • 1
  • Steven V. Kokelj
    • 3
  • Richard A. Sims
    • 4
  1. 1.Canada Centre for Mapping and Earth Observation (CCMEO)Natural Resources CanadaOttawaCanada
  2. 2.School of Environmental StudiesUniversity of VictoriaVictoriaCanada
  3. 3.Northwest Territories Geoscience OfficeGovernment of the Northwest TerritoriesYellowknifeCanada
  4. 4.Tetra Tech EBAVancouverCanada

Personalised recommendations