Evs2011 talk two_transects20110404(3)


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Walker et al. EVS Rome 2011 Talk

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  • Martin Kopecky address: Department of Botany, Faculty of Science, Charles University in Prague, Benatska 2, CZ-128 01 Praha 2, Czech Republic; Department of Vegetation Ecology, Institute of Botany, Academy of Sciences of the Czech Republic, Lidicka 25/27, CZ-602 00 Brno, Czech Republic; Good afternoon. This talk presents some of the early results from two polar transects conducted during the Greening of the Arctic IPY Initiative. We look at the spatial and temporal variation of NDVI during the period 1982-2010 and compare them with ground measurements along the transects. Before I get started though, I would like to thank the co-authors on the paper who are shown here and also the many other participants in the project,
  • The focus of this talk is the ground measurements of biomass, NDVI, and leaf area index and their correlations with observations from space mainly with the Advanced Very High Resolution Radiometer measurements.
  • The map in the lower left shows the location of the North America and Eurasia Arctic transects. North America Arctic Transect: Completed in 2006 as part of the Biocomplexity of Arctic Patterned Ground Ecosystems Project (NSF). Eurasian Arctic Transect: Field seasons in 2007-2010 (NASA).
  • Our goal was to correlate the NDVI patterns with other remote sensing data such as the summer warmth index derived from the AVHRR thermal bands and a variety of the other information such as that contained in the Circumpolar Arctic Vegetation Map GIS data base.
  • The areas that we looked at on the ground were mainly zonal sites, those where the soils and vegetation correspond to the long-term climatic climax. These photos show representative sites along the Eurasia and North America transects in each bioclimate subzone.
  • Extraordinarily Sensitive Permafrost Landscapes: Extensive nutrient-poor surface sands with lichens that are easily overgrazed by reindeer. Underlain by permafrost with massive pure ice. Extensive landslides are rapidly eroding the landscape. This exposes salt-rich and nutrient-rich clays. Complex vegetation succession process that results in willow-shrub tundra in the interior parts of the peninsula.
  • There are numerous effects of all these animals, including Overgrazing and Trampling of the vegetation Transformation of previous sedge and shrub-dominated tundra vegetation into grasslands Wind erosion of the some of he trampled areas. Some of these effects are be quantified using remote sensing tools by Timo Kumpula
  • The biomass data from the transects were examined in a couple of ways. The first is a plot-level determination, which is the of the clip harvest data from the zonal plots at each sample location. Both transects show the general expected pattern of increased biomass along the bioclimate gradient, but there are also major differences related to differences in substrate, precipitation, and relative position of the locations within each subzone.
  • These differences in structure are also evident in the LAI-Biomass relationship along both transects. An equivalent amount of biomass has consistently much higher LAI values along the NAAT than along the EAT and the difference increases at higher biomass values
  • In spite of the structural and composition differences between the transects, there is overall a very strong relationship between 1-km AVHRR NDVI values and biomass along both transects and in the combined data set.
  • Broad similarities in biomass between North America and Eurasia along Arctic temperature gradient, but also major differences likely related to different disturbance regimes, geology, and precipitation patterns. Very good correlation between AVHRR NDVI and zonal landscape-level biomass. Analysis of Landsat-derived NDVI trends for a similar period did not provide corroboration for magnitude of 1982-2010 NDVI change indicated by GIMMS 3g. AVHRR NDVI is still one of the best tools we presently have for looking at long-term terrestrial response to climate change. It is highly correlated with a wide variety of the biophysical properties, but we need better calibration of remote sensing data sets and ground measurements to give us confidence in the indicated temporal trends.
  • This project is a joint collaboration by three groups of institutions in the U.S., Russia and Finland. Five funded projects were collaborating in the project including. The primary logistic funding came from NASA and NSF in the U.S. and the Russian Academy of Science in Russia.
  • Evs2011 talk two_transects20110404(3)

    1. 1. The North America and Eurasia Arctic transects: Using phytosociology and remote sensing to detect vegetation pattern and change D.A. Walker 1 , P. Kuss 1,2 , M. Kopecky 3 , G.V. Frost 4 , F.J.A. Daniëls 5 , A. Kade 1 , C.M. Vonlanthen 1,6 , M.K. Raynolds 1 , H.E. Epstein 4 1 Institute of Arctic Biology, University of Alaska Fairbanks, 2 Institute of Plant Sciences, University of Bern, 3 Department of Botany, Faculty of Science, Charles University in Prague and Department of Vegetation Ecology, Institute of Botany, Academy of Sciences of the Czech Republic, 4 Department of Environmental Sciences, University of Virginia, 5 Institute of Biology and Biotechnology of Plants, Hindenburgplatz 55, 48149, Münster, Germany, 6 Bundesamt für Umwelt BAFU, Abteilung Gefahrenprävention, Bern, Switzerland Lecture presentation, European Vegetation Survey 20 th Workshop, Rome, Italy, 6-9 April 2011 1 An International Polar Year initiative
    2. 2. Major goal of the Greening of the Arctic project: Link spatial and temporal trends of vegetation greenness observed on AVHRR satellite images to ground observations along both transects. <ul><li>Climate </li></ul><ul><li>Vegetation </li></ul><ul><li>Soils </li></ul><ul><ul><ul><li>Permafrost </li></ul></ul></ul><ul><ul><ul><li>Spectral properties </li></ul></ul></ul>5 N-factor Biomass Plant species cover NDVI and LAI Active layer depth Soil characterization Site characterizatiion Permafrost boreholes
    3. 3. Field studies along two 1800-km Arctic transects <ul><li>USGS 1-km AVHRR data set used for the CAVM. </li></ul><ul><li>North America Arctic Transect: 2002-2006 Biocomplexity of Arctic Patterned Ground Ecosystems Project (NSF). </li></ul><ul><li>Eurasian Arctic Transect: 2007-2010, Greening of Arctic (NASA). </li></ul><ul><li>Both transects through all five Arctic bioclimate subzones. </li></ul>Bioclimate Subzones Sub- Zone MJT (˚C) Shrubs A 1-3 none B 3-5 prostrate C 5-7 hemi-prostrate D 7-9 erect dwarf E 9-12 low Map by Shalane Carlson, based on CAVM Team (2003)
    4. 4. 1-km AVHRR-NDVI patterns for the Arctic along the two transects <ul><li>General pattern of reduced NDVI with higher latitude and elevation. </li></ul>Map by Martha Raynolds & Shalane Carlson
    5. 5. Summer Warmth Index (AVHRR) Vegetation (CAVM Team 2003) Variation in climate and vegetation along the transects Map by Martha Raynolds & Shalane Carlson, based on CAVM Team (2003)
    6. 6. Zonal vegetation along both transects Eurasia Transect A - Hayes Island B - Ostrov Belyy C – Kharasavey D - Vaskiny Dachi E - Laborovaya North America transect A - Isachsen B- Mould Bay C - Green Cabin D - Sagwon MNT E - Happy Valley
    7. 7. North American Arctic Transect: part of a study of biocomplexity of arctic patterned ground Based on Walker et al. 2011 (in revision). Applied Vegetation Science.
    8. 8. Biocomplexity activities Isachsen, Ellef Ringnes I. <ul><li>CALM Grids </li></ul><ul><ul><li>Active layer </li></ul></ul><ul><ul><li>Vegetation </li></ul></ul><ul><ul><li>Snow </li></ul></ul><ul><li>Climate /permafrost </li></ul><ul><ul><li>Met station </li></ul></ul><ul><ul><li>Soil temperatures </li></ul></ul><ul><ul><li>Frost heave </li></ul></ul><ul><li>Soils </li></ul><ul><ul><li>Characterization </li></ul></ul><ul><ul><li>Nitrogen mineralization </li></ul></ul><ul><ul><li>Decomposition </li></ul></ul><ul><li>Vegetation </li></ul><ul><ul><li>Classification </li></ul></ul><ul><ul><li>Biomass </li></ul></ul><ul><ul><li>Mapping </li></ul></ul><ul><li>Remote sensing </li></ul><ul><ul><li>NDVI </li></ul></ul><ul><ul><li>Mapping </li></ul></ul><ul><li>Modeling </li></ul><ul><li>Education </li></ul>
    9. 9. Small landscape maps along climate gradient: 10 x 10 grids Raynolds, M.K., Walker, D.A., Munger, C.A., et al. 2008. A map analysis of patterned-ground along a North American Arctic Transect. Journal of Geophysical Research - Biogeosciences. 113:1-18
    10. 10. Classification of patterned-ground vegetation along the NAAT <ul><li>Summarized in three papers using the Braun-Blanquet approach. </li></ul><ul><li>Low Arctic: Kade, A., Walker, D.A., and Raynolds, M.K., 2005, Phytocoenologia , v. 35, p. 761-820. </li></ul><ul><li>High Arctic: Vonlanthen, C.M., Walker, D.A., Raynolds, M.K., Kade, A., Kuss, H.P., Daniëls, F.J.A., and Matveyeva, N.V., 2008, Phytocoenologia , v. 38, p. 23-63. </li></ul><ul><li>Synthesis: Donald A. Walker, Patrick Kuss, Howard E. Epstein, Anja N. Kade, Corinne M. Vonlanthen, Martha K. Raynolds & Fred J.A. Daniëls, 2011 (in revsion). Applied Vegeation Science </li></ul>
    11. 11. Studied contrast in vegetation on and between frost features Kade et al 2005 Deadhorse Subzone C Braya purpurascens-Puccinellia angustata community Dryas integrifolia-Salix arctica community Nonsorted Circle Between Circles
    12. 12. Frost-boil plant communities, soil and site information Kade et al. 2005, Plant communities and soils in cryoturbated tundra along a bioclimate gradient in the Low Arctic, Alaska. Phytocoenologia , 35: 761-820. Plant communities Soil and site data
    13. 13. Ordination of zonal patterned ground vegetation: controlling environmental gradients <ul><li>NMDS ordination. </li></ul><ul><li>Clear gradient of vegetation response to cryoturbation within each subzone and clear floristic separation between subzones. </li></ul><ul><li>But no clear overall controlling factors for the whole data set. </li></ul><ul><li>Floristic separation between Alaska and Canada portions of the gradient due to different floristic provinces, and substrate differences. </li></ul>Patterned-ground features Between patterned-ground features Intermediate Walker et al. 2011 in revision. Applied Vegetation Science.
    14. 14. A few of the conclusions from the NAAT vegetation studies <ul><li>Vegetation is the principal factor affecting thermal differentials between the centers and margins of small patterned-ground features and strongly affects the types of patterned ground features that are dominant within zonal Arctic landscapes. </li></ul><ul><li>Recognizing characterizing and classifying the small-scale plant communities within respective microhabitats was essential for understanding the biological and physical controls of patterned-ground morphology. </li></ul><ul><li>The zonal patterned-ground vegetation complexes (combined microhabitats) were useful for landscape and regional-level comparisons, such as comparison of floristic richness in zonal landscapes, or for extrapolation of information collected at plot scales (such as biomass and NDVI) to larger regions. </li></ul>
    15. 15. The Eurasian Arctic Transect: <ul><li>Part of an IPY study to examine the linkages between changing Arctic sea-ice conditions, summer land temperatures, and vegetation </li></ul><ul><li>2010 expedition to Hayes Island, Franz Josef Land, completed parallel transect studies in North America and Eurasia. </li></ul>
    16. 16. 1. Extensive nutrient-poor surface sands with lichens that are easily overgrazed by reindeer. 2. Underlain by permafrost with massive pure ice. 3. Extensive landslides are rapidly eroding the landscape. 4. This exposes salt-rich and nutrient-rich clays. 5. Complex vegetation succession process that results in willow-shrub tundra and much greener vegetation in the eroded valleys. High-ice Permafrost Landscapes of the Yamal Peninsula Photos: D.A. Walker and M. Liebman (upper right)
    17. 17. Reindeer effects on greenness patterns: Photos: Bruce Forbes. Overgrazing Trampling Grassification Wind erosion <ul><ul><li>Effects on reindeer on NDVI are unknown at present because of lack of control areas to study the effects (exclosures). </li></ul></ul><ul><ul><li>Potential major effect in sandy areas. </li></ul></ul>
    18. 18. Typical layout of transects and plots at each EAT site <ul><li>Sampled loamy and sandy sites within each subzone. </li></ul><ul><li>Five 50-m transects </li></ul><ul><li>Five 5 x 5-m plots (relevés) </li></ul><ul><li>Biomass harvests in each plot (x) </li></ul><ul><li>iButtons for n-factor in corner of each plot (•) </li></ul><ul><li>Soil pit in SW corner </li></ul>Soil pit
    19. 19. NMDS Ordination of all EAT study plots based on floristic similarity a, b, c, d, e: Bioclimate subzones <ul><li>Subzone A floristically distinct from the rest of the gradient. </li></ul><ul><li>Plots organized along the Axis 1 by summer warmth, and along the second axis by soil texture, reflecting the sampling strategy. </li></ul>Sandy Loamy Increasing summer warmth
    20. 20. Full data set: Axis 1: Complex biomass / summer-warmth gradient Subzone C Subzone D Subzone B Subzone E <ul><li>Axis 1 most strongly correlated with total biomass. </li></ul><ul><li>Also, summer warmth, NDVI, LAI, disturbance, active layer thickness, species richness. </li></ul>Subzone A Total Biomass (g m -2 ) Summer warmth (˚C mo)
    21. 21. Full data set: Axis 2: Complex soil moisture, soil texture, N, organic matter gradient Vol. soil moisture (g cm -3 ) <ul><li>Soil moisture </li></ul><ul><li>Total N </li></ul><ul><li>Total C </li></ul><ul><li>Pct. sand </li></ul>N and C (%) Sand (%)
    22. 22. Biomass space: Yamal plots only (excluding FJL) Total Biomass (g m -2 ) <ul><li>Total shrub biomass </li></ul><ul><li>Total graminoid biomass </li></ul><ul><li>Field NDVI </li></ul>Bryophyte biomass Lichen biomass Field LAI <ul><li>Field NDVI is most strongly correlated to total biomass. </li></ul>
    23. 23. Toward a synthesis of the two transects <ul><li>Although the research along the two transects had different objectives. There is a common primary data set from both transects: </li></ul><ul><ul><li>Vegetation, soils, and site factors from zonal vegetation along the complete Arctic bioclimate gradient. </li></ul></ul><ul><ul><li>Ground measurements of key plant productivity variables: biomass, LAI, and NDVI. </li></ul></ul><ul><ul><li>A circumpolar remote-sensing data set that contains vegetation, land temperatures, and NDVI data for both transects and changes in NDVI since 1982. </li></ul></ul><ul><li>This allows us to compare the spatial and temporal trends in vegetation, biomass, and NDVI between the two transects in response to ongoing changes in climate and land-use. </li></ul>
    24. 24. Synoptic tables for NAAT and EAT NAAT EAT <ul><li>Only a few taxa were diagnostic for the same subzone along both transects: </li></ul><ul><ul><li>Subzone A: </li></ul></ul><ul><ul><li>Cerastium arcticum </li></ul></ul><ul><ul><li>Draba subcapitata </li></ul></ul><ul><ul><li>Saxifraga cernua </li></ul></ul><ul><ul><li>Subzone E: </li></ul></ul><ul><ul><li>Betula nana/exilis </li></ul></ul><ul><ul><li>Empetrum nigrum </li></ul></ul><ul><ul><li>Salix phylicifolia/pulchra </li></ul></ul><ul><li>But many more for the broader High Arctic, Low Arctic groups of subzones. </li></ul>
    25. 25. Compared to NAAT, EAT has : <ul><li>Less biomass in subzone A (Wetter, much colder). </li></ul><ul><li>More biomass in subzone C, (Wetter, unglaciated landscape along the EAT.) </li></ul><ul><li>Much more biomass in subzone E. </li></ul><ul><li>Fewer evergreen shrubs and lichens. (Reindeer?) </li></ul>Plot-level biomass trends along EAT and NAAT NAAT EAT
    26. 26. Comparison of EAT and NAAT Leaf Area Index vs. Biomass <ul><li>An equivalent amount of biomass has consistently much higher LAI values along the NAAT than along the EAT and the difference increases at higher biomass values. </li></ul><ul><li>Reflects the different structure of the vegetation along the two transects. Higher proportion of the total biomass is non-green along the NAAT (more wood, standing dead, hairy leaves, brown moss, evergreen shrubs and lichens). </li></ul>
    27. 27. Almost identical correlation between AVHRR NDVI and biomass along the two transects Raynolds et al. 2011 submitted. Geophysical Research Letters.
    28. 28. Circumpolar aboveground biomass derived from NDVI Raynolds et al. 2011 submitted, Geophysical Research Letters
    29. 29. Conclusions <ul><li>There are broad similarities in community composition and structure between North America and Eurasia transects, but also major differences related to different disturbance regimes, geology, and precipitation patterns. </li></ul><ul><li>The Eurasia transect is much more homogeneous in the middle part of the transect (subzones B, C, D) than the NAAT. </li></ul><ul><li>Based on these data, it is not possible to define distinct zonal plant communities, except at the ends of the gradient in Subzones A and E, which are similar on both transects. The middle parts of the gradients have few good diagnostic taxa. </li></ul><ul><li>Ordination analysis reveals strong relationships between field-NDVI and total live biomass. </li></ul><ul><li>There is also a very strong correlation between AVHRR NDVI and zonal landscape-level biomass, that is nearly identical along both transects, which gives us good confidence in the biomass of zonal sites as depicted on our biomass map of the Arctic. </li></ul><ul><li>This study has shown the feasibility of studying and monitoring zonal landscape-level biomass and NDVI across the full Arctic bioclimate gradient. </li></ul>
    30. 30. Collaborations <ul><li>Institutions: </li></ul><ul><ul><li>University of Alaska </li></ul></ul><ul><ul><li>University of Virginia </li></ul></ul><ul><ul><li>Earth Cryosphere Institute (RAS), </li></ul></ul><ul><ul><li>Arctic Centre, Rovaniemi </li></ul></ul><ul><ul><li>Agriculture and Agri-Foods, Canada </li></ul></ul><ul><ul><li>University of Münster </li></ul></ul><ul><ul><li>Masaryk University, Brno </li></ul></ul>2 <ul><ul><li>Funding </li></ul></ul><ul><ul><li>U.S.: NSF, NASA </li></ul></ul><ul><ul><li>Finland: ENSINOR </li></ul></ul><ul><ul><li>Russian Academy of Science </li></ul></ul><ul><ul><li>Synthesis data analysts: Patrick Kuss, Martin Kopecky and JJ Frost </li></ul></ul>