7. Succession Flashcards
What is succession?
Patterns of abundance change with ecological time
Is succession seasonal?
No, has no season or cyclical cycle
What are the 3 types of succession?
Autogenic, Allogenic, degradative
What is autogenic succession?
Self origin, species sequence occurring where change brought about by the biota themselves
What is Allogenic succession?
Other origin, species resulting from outside,
Usually abiotic, changes to the environment
What is degradative succession?
Occurs when new and degradable resources are used successively by a number of species
How do salmon provide nutrients to the surrounding habitat?
Nutrients leach into the ground, extra nitrogen and sustinance for the trees
What is primary succession?
Occurs on landforms where no remnants of a previous community exist e.g lava flows
What is secondary succession?
Occurs in space opened by complete or partial removal of species, but where resources and propagalues remain, e.g tree falls
What are the stages of succession?
Bare ground, pioneer stage, seral stages, climax
Where can cyclic cycles of succession can occur along the stages
Seral and climax
Which stages do good colonists thrive at?
Pioneer stage
What are good colonists?
Poor competitors
High growth rate, small, wide dispersal, fast growth, short lived
What are Poor Colonists?
Good competitors
Slow growth, Large size, limited dispersal, slow population growth, long lived, K selection
What are the mechanisms that drive ecological succession
Facilitation,
Tolerance,
Inhibition
What is facilitation?
Early successional species make the environment more suitable for recruitment for late successional species
How does the bears feeding habit help grow and provide nutrients to trees?
Just bite the head of salmon, decomposing fish gives nutrients to the trees
What is the time scale of primary succession?
10-100 years
Is primary succession nominated by few or many species?
Few
How does primary succession work for animals/plants
A-B-C-D, always one dominant species, outdoos the other
How does secondary succession work for animals/plants?
Abcd-Bcd-Cd-D
What is inhibition?
Early successional species make the environment less suitable for others
When does inhibition occur?
Occurs where competitively similar species are present, holds the site against all others till they die out
What is successional tolerance?
A species neither facilitates nor inhibits its successors, occurs where competitive hierarchies exist
What starts the process of succession?
Disturbance
How can we document succession?
Observe or infer
What is an example of facilitation?
Plant succession following glacial retreat
What is an example on inhibition?
Seaweed succession on rocky shores
What is an example of tolerance?
Old field succession
How much have glaciers in SE Alaska retreated by since 1750?
120km
What does the glacier expose which is used as soil?
Glacial till
What characterises the soil?
Low nitrogen and nutrient content
Why is glacier bay in Alaska a good example of primary succession?
Clear movement of ice shows clear stages, 98% of tourists travel by boat so no damage by humans
After 5-10 years what does the bare glacial ground look like?
Colonised by pioneer species, Cyanobacteria. Lichens, dwarf fireweed and misses, nitrogen fixing plants
What happens to glacier bay after 20 years?
Pioneer flowers bloom such as mountain aven, thin grass cover
What happens to glacier bay after 30 years?
Small bushes and trees, moderate grass cover, thin soils, trees have yellow leaves due to stress
What happens to glacier bay after 60 years?
Larger trees and forests, alder, willows, cottonwood, leaves create a build of of soil
What happens to glacier bay after 100years ?
Larger trees, developed soil, alder, spruce, standing biomass, cold rainforest, very acidic soil
What happens to glacier bay after 200 years?
Developed forest, spruce trees. Hemlock
How deep is soil in glacier bay after 200 years?
15.1cm
What does the melting of these glaciers create?
New streams and rivers
What is a remnant glacier?
Static glacier at the tops of mountains
What happened to the stream?
More species inhabited it over years
Why does the river warm up over time?
Melt water gets hotter
Which seaweed dominated succession of rocky shores?
Green ulva
What competes with ulva as the successional period gets older
Gigartina
What is gigartina better at?
Surviving rough and tough conditions
What is ulva threatened by?
Storms and crabs
How did old field sites form in the US?
Pre colonial mixed hardwoods destroyed by frontier farmers6
What happened to frontier farmers as they moved west?
Exposed fields were colonised by pioneers and regeneration ensued
What is the typical sequence in old fields?
Annual weeds, herbaceous perennials, shrubs, early trees, late trees
What is the most common pioneer annual in old fields?
Ragweed
What is the drawback if ragweed?
Cannot persist under canopy light
What is the benefit of late successional plants
Shade tolerant
What is the climax state?
The final or stable community in a successional series
What is the monoclimax theory?
Succession is directional and predictable, resulting in a single climax?
What is polyclimax theory?
Many different climax communities can arise and are controlled by soil moisture,
Mineral ions activity of animals and topography
What is climax pattern hypothesis?
Continuum of climax theory that varies along environmental variants
What is alder in relation to spruce?
Inhibitor
