L3 Post-Glacial History of British Flora Flashcards
what time period is he ice age in
quaternary
What is the name for the current interglacial period and how long has it been going on for
The Holocene
11,700 years
Which direction was the movement of continental land mass in the Quaternary period
Migration towards polar regions
What mountainous region formed in the Quaternaty period and what did it cause
Himalayas
Led to significant cooling
3 main events that occured in the Quaternary period
Migration of continental mass towards poles
Uplift of Himalayas
Closing of the Isthmus of Panama
What change did the closing of the Isthmus of Panema bring about
Changes to ocean circulation
What causes repeated glaciations
Milankovitch cycles
What is involved in the Milankovitch cycles that causes glaciations
Eccentricity
Obliquity
Precession of the equinox
What is eccentricity
Shape of earth’s orbit around the sun
Changes over time: sometumes circular, sometimes more eliptical
What is obliquity
The tilt of the earth in relation to its plane of orbit
What is meant by precession of the equinox
The season during which the earth is closest to the sun varies over time
What happened to plants in the glaciated regions
Wiped out
Only species in the refuga survivef and repopulated
What was the last major tree to migrate back after the ice age and why
Beech
Has very large seeds so is much slower a spreading
What is studied in palaeoecology
Ecology of the past
Ways to study palaeoecology
Terrestrial sediment cores
Ice cores
Sediments
Tree rings
Fossil pollen
Macrofossils (plant parts)
Charcoal
Fossil beetles
Stable isotopes
How is sediment used in palaeoecology
Sediment is extracted as a tube of earth
Take samples along different points of the tube = different points in time
What is the benefit of takinf samples from an anoxic environment
Preserves fossils
How are the sediment tube samples processed in the lab (what is added to them and what does it do)
Hydrochloric acid added - breaks down everything except pollen as pollen contains highly resistant sporopollenin
What is the Clements Gleason debate about
What is Gleasons’ view point and is it supported by palaeoecology
Wheterh plants behave as one organism
Gleason argues that species are individualistic and just happen to occur together at certain points in time
This is supported by palaeoecology as it shows species arrive and dominate at different times and different rates
What is the possible origin of pine in Scotland
Glacial refuge off coast of Scotland which reestablished species
What was the woodland structure of Britain in the early postglacial period
Treeless steppe-tundra flora with Arctic/Alpine flora
What was the woodland structure of British woodlands 11000-10000 YA and what was the climate
Increase in juniper, birch, pine
Climate cold, becoming continental
what was the climate in the pre-boreal period
cold but becoming continental
explain what changes were seen in vegetation 10000-8000 BP
rapid rise in hazel
appearance of oak and elm
what was the climate 10000-8000BP
continental
How many years ago did Britain seperate from the European continent
8000-6000
What was the climate 8000-6000BP and what plant structure dominated
Climate warm and wet, oceanic
Wildwood forests
At what time was the most complete wildwood development
5000BP
What percentage of the UK is covered by woodland and how much of this is ancient
13%, majority conifer plantation
Only 1.2% ancient
7 main trees dominating wildwood uk
Alder
Ash
Lime
Hazel
Oak
Pine
Birch
Where was Alder found 5000YA
Major river valleys and wetlands
Where was Ash found 5000YA
Calcerous soils in S and E England
Where was Lime found 5000YA
Fertile, non-calcerous soil in England and Wales
Where was hazel found 5000YA
Calcerous soils beyond the range of Ash
Where was Oak found 5000YA
Acidic infertile soil
Where was pine found 5000YA
Western and Northern Ireland and Scotland
Where was Birch found 5000YA
Why was it often out-competed
Extreme limits of woodland growth (Northern Scotland)
Low shade tolerance
What events occured after 5000BP
Forest clearance
Easy agriculture
Blanket bog spread
What types of pollen increased and decreased
Decrease in tree pollen
Increase in graminoid pollen (grasses, cereals)
