Lec 5 Flashcards
Major landscape building features in Northern Systems
Glaciation and de-glaciation
Permafrost and melting permafrost
Pleistocene Glaciation coverage
30 percent of the world
Current glaciation in the world
11 percent
Wisconsin Glaciation
Covered most of the northern half of North America
Most recent glaciation (20k years ago)
Time since glacial cover highly variable- some areas or still covered others melted thousands of years ago
Northern ecosystems are relatively
Young
Laurentide Ice Sheet
Eastern North America
Cordilleran Ice sheet
Western North America
De- glaciation created
Creation of water systems and ecosystems
Fish and other species migrated north to fill out these systems
Tree species also dispersed into the North
Glaciation
Strips away soil, creates lake basins and riverbeds
Receded 20k years ago and forest gradually took over in Canada
Left strong imprints on the North
Boreal forest is only how many years old
5k
Evidence of glaciation
Glacial fluting
Glacial moraines
Raised beaches
Eskers
Permafrost
Earth material that has been below 0 degrees for more than 2 years so has become ice cemented
More permafrost
Farther north
Except in areas with Peatlands that provide ventilation
Permafrost continuous zone
Permafrost is everywhere
Discontinuous zones
Permafrost is spatially sporatic
Permafrost needs
Cold temperatures
Active layer
Where plants can grow
More of this the farther south you go
Why are peatlands so prevalent in the North
Permafrost restricts movement of water
Flat terrain can reduce water flow
Short summers and cold temperatures reduce rates of decomposition
3 conditions for a peatland to form
Annual precipitation must be greater than 500mm
Annual temp cannot be too hot
Positive water balance
Permafrost areas have an abundant amount of
Soil water that cannot be drained due to permafrost underneath
Bog
A peatland that gets water from rain/snow falling
Water table at or slightly below surface
Low mineral content
Bog water is very
Acidic due to organic acids from decomposition
Paludification
The conversion of dry lands into peatlands
The drowning or submergence of upland ecosystems
Limiting factors for plants in peatlands
Waterlogged (low oxygen)
Poor nutrients
High in toxins
Acidophiles
Plants that thrive in acid environments
4 types of bogs
Basin
Domed
Palsa
Peat plateau
Spruce bog
Pond border bog- will likely become a basin bog
Black spruce, tamarack, and Labrador tea can tolerate conditions
Formation of domed bog
Bogs fill area but peat continue to develop
Spread beyond original area
Palsa
Has an ice core
A mound of peat that develops as a result of the formation of a number of ice lenses beneath the surface
Fen
A peatland which is influenced by water outside its own limits
Why to fens have greater plant diversity
Water is moving
High nutrients
Rich fens are
Alkaline while poor are acidic
Wetland development is function of
Climate
Geomorphology (Landform)
Hydrology
Chemistry
Biology
Swamps
Forested wetlands, peatlands
Not as wet as fens, bogs, marshes
Associated with rivers, lakes and waterways
Why are marshes and swamps usually found in more southern regions than peatlands
Because decomposition is temp dependent
Marsh
Shallow surface water whose level fluctuates
Little accumulation of peat, high productivity, high decomposition
Herbaceous vegetation
