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Evs2011 talk two_transects20110404(3)
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Walker et al. EVS Rome 2011 Talk
Edie BarbourSuivre
chief c&bw à Alaska Geobotany CenterPublicité
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Evs2011 talk two_transects20110404(3)
- 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
- 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)
- 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
- 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.
- 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
- 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
- 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
- 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)
- Almost identical correlation between AVHRR NDVI and biomass along the two transects Raynolds et al. 2011 submitted. Geophysical Research Letters.
- Circumpolar aboveground biomass derived from NDVI Raynolds et al. 2011 submitted, Geophysical Research Letters
Notes de l'éditeur
- 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.
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