16 results found Displaying all 16 entries
Circumpolar Arctic Substrate pH
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Alaska Geobotany Center (AGC)
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Differences in substrate chemistry have important effects on dominant plant communities. Some of the most important effects are related to soil pH, which governs the availability of essential plant nutrients. Soils in the circumneutral range (pH 5.5-7.2) are generally mineral rich, whereas the full suite of essential nutrients are often unavailable in acidic soils (pH < 5.5) or in soils...
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2019-08-19 14:04:17 -0800
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Data
Circumpolar Arctic AVHRR Summer Warmth Index 1982-2003 (Raynolds et al. 2008)
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Alaska Geobotany Center (AGC)
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This data set was calculated from monthly AVHRR thermal infrared data (Comiso 2003). Summer Warmth Index (SWI) is the sum of monthly mean temperatures above 0 degrees Celsius. The months of May-September were evaluated for the years 1982 - 2003 (Raynolds et al. 2008).
Back to [Circumpolar Arctic Vegetation Map](/catalog/entries/5503-circumpolar-arctic-vegetation-map-cavm-team-2003)
**Map...
Complete
2019-08-15 13:37:09 -0800
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Data
Circumpolar Arctic Bioclimate Subzones
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Alaska Geobotany Center (AGC)
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A fundamental problem for the CAVM is how to characterize the transitions in vegetation that occur across the roughly 10 °C mean July temperature gradient from the tree line to the coldest parts of the Arctic. Various authors, working with different geobotanical traditions, have divided the Arctic into bioclimatic regions using a variety of terminologies. The origins of these different terms...
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2019-08-16 12:51:25 -0800
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Data
Circumpolar Arctic Floristic Provinces Map
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Alaska Geobotany Center (AGC)
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Floristic sectors characterize the considerable east-west floristic variation within the subzones. The more northern Arctic bioclimate subzones have a relatively consistent core of Arctic plant species that occur around the circumpolar region. Further south, local east-west variation is related to a variety of factors, including different paleohistories and the greater climatic heterogeneity....
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2019-08-16 12:53:02 -0800
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Data
Circumpolar Arctic AVHRR NDVI Trend 1982-2008 (Bhatt et al. 2010)
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Alaska Geobotany Center (AGC)
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The normalized difference vegetation index (NDVI) is a measure of greenness. NDVI was calculated as: NDVI = (NIR - R) / (NIR + R), where NIR is the spectral reflectance in the AVHRR near-infrared channel (0.725-1.1 µm, channel 2) where light-reflectance from the plant canopy is dominant, and R is the reflectance in the red channel (0.5 to 0.68 µm, channel 1), the portion of the spectrum where...
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2019-08-15 13:35:35 -0800
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Data
Circumpolar Arctic AVHRR False Color-Infrared (CIR) Map
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Alaska Geobotany Center (AGC)
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Advanced Very High Resolution Radiometer (AVHRR) data were obtained from the USGS Global AVHRR 10-day composite data. (http://edcdaac.usgs.gov/1KM/1kmhomepage.asp) (Markon et al. 1995). Glaciers and oceans were masked out using information from the Digital Chart of the World (ESRI 1993). The image is composed of 1 x 1-km pixels. The color of each pixel was determined by its reflectance at the...
Complete
2019-08-16 12:49:41 -0800
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Data
Circumpolar Arctic Elevation Map
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Alaska Geobotany Center (AGC)
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Elevation strongly influences soil moisture and patterns of tundra plant communities. Areas less than 100 m above sea level were separated to show low-elevation plains. Areas above 100 m elevation were divided into 333-m intervals to show decreases of about 2 °C, as predicted by the adiabatic lapse rate of 6 °C per 1000 m. This corresponds to the change in mean July temperature between...
Complete
2019-08-15 13:50:14 -0800
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Data
Circumpolar Arctic AVHRR NDVI Map
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The normalized difference vegetation index (NDVI) is a measure of greenness. NDVI was calculated as: NDVI = (NIR - R) / (NIR + R), where NIR is the spectral reflectance in the AVHRR near-infrared channel (0.725-1.1 µm, channel 2) where light-reflectance from the plant canopy is dominant, and R is the reflectance in the red channel (0.5 to 0.68 µm, channel 1), the portion of the spectrum where...
Complete
2019-08-02 13:49:35 -0800
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Data
Circumpolar Arctic Lake Cover Map
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Alaska Geobotany Center (AGC)
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Lake cover strongly affects the reflectance of the land surface over large areas of the Arctic, and was useful for identifying extensive wetlands. Lake cover was based on the number of AVHRR water pixels in each mapped polygon, divided by the number of pixels in the polygon. Since the imagery has a pixel size of 1 km^2, lake cover is underestimated for areas with many small lakes. Pixels within...
Complete
2019-08-16 12:48:07 -0800
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Data
Circumpolar Landscape Age Map (Raynolds et al. 2008)
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Alaska Geobotany Center (AGC)
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The landscape age map shows the length of time (in thousands of years) that Arctic landscapes have been available for plant colonization and the development of plant communities (Raynolds et al 2008). For most areas, this would be the time since the most recent deglaciation. Other areas first became available for plant colonization after emerging from under water due to drainage of glacial...
Complete
2019-08-16 12:55:40 -0800
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Data
Circumpolar Arctic Coastline and Treeline Map
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Alaska Geobotany Center (AGC)
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The map extent is the Arctic, defined as the Arctic Bioclimate Zone, the area of the Earth with tundra vegetation and an Arctic climate and Arctic flora. It excludes tundra regions that lack an Arctic flora, such as the boreal oceanic areas of Iceland, the Aleutian Island, and the alpine tundra regions south of latitudinal tree line. Tundra is a physiognomic descriptor of low-growing vegetation...
Complete
2019-08-16 12:53:51 -0800
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Data
Circumpolar Arctic Landscape Map
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Alaska Geobotany Center (AGC)
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The landscape map was derived from topographic data, regional physiographic maps, and visual interpretation of the AVHRR false-CIR image. Landscape codes were assigned to each of the vegetation polygons. For Greenland, Russia and the United States, detailed landscape maps formed the basis of the vegetation polygons (see vegetation mapping section). However, these regional landscape maps did not...
Complete
2019-08-19 14:03:55 -0800
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Data
Circumpolar Arctic Biomass (Raynolds et al 2012)
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Alaska Geobotany Center (AGC)
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This map portrays an estimate of above ground plant biomass for the tundra biome based on trans-Arctic field data and AVHRR NDVI (Raynolds et al. 2012). Aboveground phytomass was sampled on transects along the Arctic bioclimate gradient in North America (1750 km long, 8 locations sampled 2003–2006) and Eurasia (1500 km, 5 locations sampled 2007–2010). The study locations were chosen to...
Complete
2019-08-15 13:30:05 -0800
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Data
Circumpolar Arctic Vegetation Map (CAVM Team 2003)
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Alaska Geobotany Center (AGC)
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The Circumpolar Arctic Vegetation Map (CAVM) is a geoecological map of the entire Arctic with a unified legend. It is the first vegetation map of an entire global biome at a comparable resolution. It was funded by the US National Science Foundation (OPP-9908-829), the US Fish & Wildlife Service, the US Geological Survey and the US Bureau of Land Management.
The CAVM region is north of the...
Complete
2019-08-26 13:22:51 -0800
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Data
Circumpolar Arctic Vegetation Map (Vegetation Layer)
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Alaska Geobotany Center (AGC)
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Mapped polygons at 1:7.5 million scale contain many vegetation types. The map portrays the zonal vegetation within each mapped polygon. Zonal sites are areas where the vegetation develops under the prevailing climate, uninfluenced by extremes of soil moisture, snow, soil chemistry, or disturbance, and are generally flat or gently sloping, moderately drained sites, with fine-grained soils...
Complete
2019-08-16 12:56:27 -0800
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Data
Circumpolar Arctic Biomass Trend 1982-2010 (Epstein et al. 2012)
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Alaska Geobotany Center (AGC)
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Trend in Arctic biomass was calculated from a linear regression of biomass values for all years 1982-2010 (Epstein et al 2012). Pixels with significant trends (p < 0.05) were retained. Biomass was calculated from the relationship between AVHRR NDVI and ground sampling of biomass, as described below: Aboveground phytomass was sampled on transects along the Arctic bioclimate gradient in North...
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2019-08-15 13:31:21 -0800
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Data