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Updated 11/03/98

Criteria used to infer "rules-based" vegetation

Any pollen assemblage which does not fall into the categories listed below is mapped as "Unclassified".  As the classifications are made, a site is given the first classification for which it qualifies.  Any subsequent classifications are ignored.  Please note that the cutoffs are based on lake samples. Because depositional environments differ in the size of their pollen catchments and sometimes in the quality of pollen preservation, chances of erroneous or non-classification of non-lake fossil samples may occur.

Alaska
Spruce forest-tundra
  • 5-10 % Picea
Spruce forest
  • > 10 % Picea
Balsam Poplar forest-tundra
  • > 1 % Populus
  • < 5 % Picea
  • Betula Present
  • Salix Present
Grass-shrub tundra
  • < 5 % Picea
  • 20 - 40 % Alnus + Betula
  • > 20 % Cyperaceae + Poaceae
Birch-Willow-Heath tundra
  • < 5 % Picea
  • > 40 % Betula + Alnus
  • < 20 % Cyperaceae + Poaceae
Grass tundra
  • < 20 % Betula + Alnus
  • > 20 % Cyperaceae + Poaceae
  • < 10 % Other herbs
Russia
Grass tundra
  • > 40 % Cyperaceae + Poaceae
  • < 10 % Betula + Alnus
  • > 5 % Other herbs
Grass-shrub tundra
  • 20 - 40 % Cyperaceae + Poaceae
  • 10 - 40 % Betula + Alnus
Birch-Willow-Heath tundra
  • > 40 % Betula + Alnus
  • < 20 % Cyperaceae + Poaceae
  • < 10 % Pinus subg. Strobus
  • Larix Absent
Stone Pine tundra
  • > 30 % Pinus subg. Strobus
  • < 20 % Betula
  • > 20 % Alnus
Larch forest-tundra
  • < 10 % Pinus subg. Strobus
  • > 20 % Betula
  • > 15 % Alnus
Larch forest
  • Larix Present
  • > 10 % Betula
  • 10 - 30 % Pinus subg. Strobus
  • > 15 % Alnus