biomes - university of oregon geography 11.pdf · 2005-04-20 · northern conifer forest/taiga....
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Biomes
Arctic Tundra
Houghton and Skole (1990) and Schlesinger (1997)
Tundra
• Lowest diversity (# species/area) 3% worlds species
• Lowest net primary production (10-400 g/m2/yr)
• Limited harsh environment
• Growing season: 2-3 months
• Soils—permafrost, inceptisols and entisols
Tundra regions:
Climate
Mean annual Temp -20 C to -50 C
Mean annual Ppt10-50 cm
Moisture source: summer rain & thaw
• short growing season (6-10 weeks)• 2 months of continuous daylight• long, cold, dark winters
Climograph
Barrow, AlaskaElevation: 31 feet
Latitude: 71 18N Longitude: 156 47W Ft - Tundra
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Mean annual temp = -20º C to - 50 º C
Mean annual precipitation = 10 to 50 cm (mostly summer & snow melt)
Mechanical weathering poor soil development
Entisols/Inceptisolspoorly developed
Inceptisols: “embryonic” soilsEntisols: recent soils
Photo from USDA NRCS
Perennial, dark colored leaves
Lichen: symbiotic relation between algae and fungus
Colorado Rockies
Alpine Tundra•Thin soils •Different climate from Arctic Tundra•Freeze-thaw cycles operate on diurnal & seasonal cycle
Arctic Animals
Rangifer tarandus Ovibos moschatus
Ursus arctosBranta ruficollis
Arctic Tundra vs. AlpineHigh latitudes (lowlands & highlands) Mountain Tops mid and low latitudes
Large land area Small land area
Short growing season b/c of day length Short growing season b/c snow pack
Low light intensity High light intensity (especially UV)
Less precipitation Greater precipitation (as snow)
Permafrost Permafrost is rare
Human impacts in the Arctic• Warmer temperatures cause accelerated thermokarst
erosion = subsidence of terrain caused by thawing of frozen ground
• Little impact prior to 19th century. Native people maintained low population density
• Three periods of human impact in the Arctic:Early mining period (Alaska Gold Rush – 1870 to 1920s)WW II Military bases built throughout Alaska (1930s and 1940s)Oil and Natural Gas exploration (1960’s to present)
Northern Conifer Forest/Taiga
Houghton and Skole (1990) and Schlesinger (1997)
Fort Nelson, British ColumbiaElevation: 1253 feet
Latitude: 58 50N Longitude: 122 35W E - Boreal, Subartic
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Ottawa, OntarioElevation: 374 feet
Latitude: 45 19N Longitude: 075 40W Dcb - Moist Continental
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Saint John, New BrunswickElevation: 358 feet
Latitude: 45 19N Longitude: 065 53W Dcb - Moist Continental
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Climate considered “subarctic”growing season temperatures are coolannual precipitation is low (25-75 cm )
Precipitation:Continental(dry)Maritime(moist)
Temperature:Tropical (warm)Polar (cold)Arctic (very cold)
Source Regionsfor North AmericanAir Masses
Boreal Forest/Taiga
• 45 to 70 degrees Latitude• Low diversity (2-4 tree species)• NPP (400-2000 g/m2/yr)• Limited by growing season to north (3-4
months/yr); competition to south• Soil: spodosol (podzolization)
Podzolization
Moderate Precipitation
Iron rich hard pan layer
O = organicA = humus/clayE = wash out (eluviation)B = accumulation (illuviation)C = weathered bedrockR = Regolith or bedrock
General Soil horizons
Common trees of the boreal forest
Vegetation adaptations:evergreen needleafthick cuticle – xeromorphic leaves