The Alaska Vegetation Classification - Alaska Geobotany Center ...

TilCAn unstratified, nonsorted deposit of gravel, boulders, sand and finer materialsthat has been transported and laid down by glacial ice with little or no transportationor sorting by water.Till plain-An extensive flat-to-undulating area underlain by glacial till.TlmberllneSome consider the upper edge of continuous forest to be timberline;others recognize timberline as the altitude of the highest tree or a midpoint betweenthese extremes.ToleranceThe relative ability of a plant species to survive and develop under adeficiency of an essential growth requirement, such as light, moisture, or nutrientsupply.Tre&A woody perennial plant, typically large (a mature height of at least 3 meters[lo feet]) and with a single well-defined stem and a definite crown shape.Tree Ilne-A loose term for the limit beyond which trees cannot or do not occur.Tree line is more generally used lo refer to the altitudinal boundaty, and the term'Tree limit" is used for the latitudinal boundary.Tree, dwarf-In the Alaska vegetation classification, a plant species that would,under normal conditions, be a tree but which will not achieve a height of 3 meters(10 ft) on the site where found; for example black spruce on bogs or near treeline.TundrsA cold-climate landscape having a vegetation without trees. The absenceof trees is caused by a complex of conditions that ultimately is related to regionalclimate. This regional aspect distinguishes tundra from treeless bogs where lowedaphic extremes prevent tree growth in areas within a generally forested region.Alpine tundra-That portion of the landscape above the upper limit of tree growthin the higher mountain regions that supports a plant cover of dwarf shrubs andherbs.Dwarf shrub scrub tundra--A tundra landscape (beyond the limits of treegrowth) with a dwarf shrub scrub vegetation.Herbaceous tundra-A tundra landscape (beyond the limits of tree growth) withan herbaceous vegetation.Mat and cusblon tundra-A tundra landscape (beyond the limits of tree growth)with a vegetation composed of mat and cushion plants.Sedge-grass tundra4 tundra landscape (beyond the limits of tree growth) withan herbaceous vegetation of nontussock-forming sedges and grasses.Shrub tundra-A tundra landscape (beyond the limits of tree growth) with a scrubvegetation.Tussock tundra-A tundra landscape (beyond the limits of tree growth) with anherbaceous vegetation of tussock-forming plants, particularly Eriophorurnspp.Tussock-A plant form that is tufted and bears many stems arising as a large,dense cluster from the crown.