Spatial patterns of land-surface temperature and NDVI, and their relation to vegetation distribution on the Yamal Peninsula, Russia
Martha
K.
Raynolds, Institute of Arctic Biology, University of Alaska Fairbanks, PO Box 757000, Fairbanks, Alaska 99775-7000, USA, ,, fnmkr@uaf.edu
Donald
A. (Skip)
Walker, Institute of Arctic Biology, University of Alaska Fairbanks, PO Box 757000, Fairbanks, Alaska 99775-7000, USA, ,, ffdaw@uaf.edu
(Presenting)
Josefino
C.
Comiso, Cryospheric Sciences Branch, NASA Goddard Space Flight Center, Code 614.1,, Greenbelt, Maryland 20771, USA, ,, josefino.c.comiso@nasa.gov
Arctic vegetation is largely controlled by climate, particularly summer temperatures. Satellite data can be used to calculate land surface temperatures resulting in spatially detailed maps that are an improvement over interpolated data based on few, mostly coastal weather stations. Temperature data most relevant to arctic plants between 1982-2003 was summarized as average summer warmth index (SWI = the sum of monthly mean temperatures > 0 ºC). As mapped by the CAVM, the Yamal bioclimate subzones are warmer than average for the Arctic, especially for Subzone C. A bioclimate map based on satellite temperatures shows coldest areas along the coast and in areas with many lakes. The Normalized Difference Vegetation Index (NDVI) is a measure of relative greenness and can also be calculated from satellite data. The analysis included maps created by the Earth Cryosphere Institute as part of the Circumpolar Arctic Vegetation Map (CAVM 2003) project (including landscape, Quaternary geology, soil texture), the CAVM classes, elevation, and SWI. The main trend in NDVI values is an increase from north to south, a gradient along with both temperature and elevation increase. NDVI increases about 0.0036 units for every degree of SWI, which is less than the response of the Arctic as a whole (0.0137. The increase in NDVI with elevation is mostly due to the higher elevations occurring in the areas farthest south, but also holds true on the Peninsula itself, where NDVI increases 0.0012 units for every meter in elevation. For the Arctic in general, NDVI decreases with elevation. There was no evidence of differences in NDVI due to age of surfaces as mapped by Quaternary geology, but NDVI of marine sediments were lower than NDVI of glacial and glacio-fluvial deposits (0.46 vs. 0.49). A general linear model analysis showed that landscape (as mapped by “landschaft”) and elevation together accounted for 49% of the variation in NDVI among CAVM polygons . Lithology, vegetation type, SWI and percent lake area together accounted for an additional 13% of the variation.
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