Transcript Mt St Helens New life in the Blast Zone

Mt St Helens
New life in the Blast Zone
Secondary Succession
- a note taking exercise
Note taking
• Using the website [ngm.com] and then the
May 2010 National Geographic Magazine
• Make notes from the three spreads of text
and then the figure on pages 46 + 47.
• Absorb the images and THINK about the
process
• Write up your notes on plain paper or PC
to organise your thoughts into a clear and
logical account …
May 1980 – 30 yrs
•
•
•
•
51 killed, 200 square miles of forest
Situated between Mt Hood and Mt Adams
2549m
Thousands of dead trees floating on Spirit
Lake = unique environment
• Now richer than ever – tadpoles, aquatic
plants + 20” Rainbow Trout
• Elk Population have soared
Recovery
• Top 1300’ were removed, 3 billion cubic
yards mud and snow
• BUT How did fish reappear twice as long as
they were previously?
• Lake above mackinaw, below Rainbows so
how did they transfer? Were they illegally
re-introduced? – plagio climatic?
• Real questions isn’t how they got there?
but how they got so big?
Primary Colonisation
• Came back to life 2004 – 2008
• Most studied large scale re-colonisation /
disturbance in the world
• Biological legacies
•
•
•
•
•
Fallen trees
Buried roots
Seeds
Gophers
Amphibians
all survived
Sampling
• Assumption forest would decolonise from
outside
• First plant discovered by Charlie Crisafulli in
1981 on the Pumice Plain.
• Quickly Foxglove and purple prairie lupin were
primary colonising producing simple food for
insects. This was followed by habitats for mice
and voles.
• Death – plants enrich ash and attract organisms
allowing others to colonize and so modify the
environment
Control
• Spring 2009 – passed to allow limited
fishing
• Saplings evident , Indian paintbrush, 15’
willow and ash, toads and tree frogs
WATER
• Macrophytes in shallows – Fish
• After explosion visibility ↓ 30@ to 6”
• Body temperature, Carbon Manganese
iron and lead = bacteria Flourished
• Microbes, aerobes ↓ [used up oxygen],
anerobes, ntrogen consuming, bacteria
feeding on methane and heavy materials.
Aquatic Change
• Stream and snow melt enters diluting the
lake – water clears, sunlight penetrates…
• Phyto Plankton ↑ so aquatic insects ↑
amphibians found, by 1990s macrophytes
grow in shallows.
• Tiny midges, freshwater snails, rainbows
reach four to five pounds in 2/3 years
New Species
• Colonise explosively only to burn out +
decline
• Predators, parasites and colonisers
compete
• Land gradually changing from grey back to
green
1.
Pocket Gophers push soil to the surface
2.
Glacier lilies rise through the ash rather than snow
3.
Flexible fir trees grow erect again
4.
Toads and burrowing animals like deer mice re-emerge
5.
Fireweed seeds take root, purple lupines add nitrogen
6.
Ballooning spiders arrive but need years to establish breeding
7.
Elk hoofs break up the soil
8.
Prey attract predators such as coyote
Plagio Climax?
•
•
•
•
Rainbow Trout eventually 20” 2 ½ lbs
World class fishery
so Proposal to award 10 licences annually
Explosive interest in the area after
eruption but this has died back – biological
recovery centre now closed
• Majority of visitors now foreigners,
Americans now day trippers
• National Park? but not static
Dynamic equilibrium
Changes remain important but sample plots
cannot represent the whole population so..
Reliant on Satellite survey; the future?
Images NGM.com
http://ngm.nationalgeographic.com/2010/05/mo
unt-st-helens/funk-text
Text National Geographic - May 2010