Ecological biogeography

Systems of ecological change:

- Disturbance:

○ Often a very important part of the long time thriving of an ecosystem

§ They are subject to change and change is constant

○ Physical (abiotic):

§ External

□ Volcanism

□ Fire

□ Wind

□ Flood

○ Biological (biotic):

§ Internal

□ Pathogens/disease

□ Consumers (trophic)

□ Humanity

® Pollution

® Source extration

® Agriculture

® Urban developments

Patterns, magnitudes & frequency:

○ Homogeneous - einsleitur

○ Ecosystems are not homogeneous

§ Some more suseptible to disturbance than others

○ Scale:

§ Micro 1-500 yrs, 1 m2-1 km2

□ Individual plants, forests, flood, earthquake

§ Meso 500-10.000 km2 - 1 km2-10.000 km2

□ Glacial and interglacial periods

§ Mega 1 million to 4,600 million yrs

□ Climate regimes and evolutionary patterns

□ Bombardment (astronomical)

□ Plate tectonics

Primary succession:

- A lifeless surface (new/blank sheet)

○ Where it all starts

○ Is progressively colonised by plants and animals

§ (t.d. scree, retreating glacier fronts, lava fields or shorlines)

Process of succession:

- Sequence of stages:

○ Sere:

§ Seral stages:

□ In order to get the woodland you have to go through all the stages

□ Facilitation (highly predictible):

® Primary succession > (to) Climax vegetation community

1. Barren landscape

2. Mosses and lichens come about

– They die and the soil develops

3. Grasses and small herbaceous plants grow

w Roots break up the rock and release nutrients

4. Shrubs colonise these soils

w Deeper soils and more water can percolate

5. Ultimately trees come to the area with deeper soils (start of a hill)

w Climax community

§ Alternative models of succession:

□ Tolerance:

® Competition

◊ How tolerant plant species are to one another

} The canopy can shade for lower growing plants and they don't thrive

□ Inhibition:

® Contra facilitation:

◊ Plants colonise an area and exlude others

□ Random :

® No facilitation or inhibition

◊ Just random.

Poly climax

- Areas have woodland and a mix of wetlands and other soil types

Mono climax

- "Every region has only one climax plant community toward which all are developing"

Autogenic succession:

- Homeostasis & homeorhesis:

○ Final stage:

§ Homeostasis

□ Stable, self-regulating & equilibrium

§ Dynamic flux:

□ Seasons, cycles, trophics & nutrients

§ Resilience:

□ Depending on magnitude and frequency

® To return to and to persist in a stable state

§ Homeorhesis

□ Dynamic stability

§ Disturbance:

□ Necessery:

® Ecosystems cannot reproduce and thrive without disturbance (til lengri tíma)

Disturbance sources:

- Fire:

○ Most common disturbance source:

§ Requires fuel and an ignition source

§ Vegetation provides the fuels for wildfire and lightning is the most common ignition source

§ Vegetation type, climate and topography will influence the behaviour of fire

§ Human ignintion:

□ T.d. cigarettes

○ Fire and biomass:

§ Vegetation structure

§ Vegetation properties:

□ Combustible resins (trjákvoða)

§ Vegetation type:

□ Coniferous woodland (könguleberandi)

§ Biomass:

□ The growing plant

□ Deadwood

□ Leaf litter

○ Fire can be an important part of the ecosystem:

§ T.d for the eucalyptus tree in Australia

- Wind:

○ Causes the most amount of damage in some forest types

○ Hurricanes

○ Tornados

§ ...when the trees fall:

□ It opens up the canopy

□ Makes areas of exposed soils bare

□ Fallen trees makes other plants able to grow on them and surrounding them

- Floods:

○ River and lake flooding:

§ High rainfall or snowmelt

○ Falsh flood:

§ High rainfall

○ Costal floods:

§ Storm surges and tides

○ Positive impacts on terrestrial ecosystems:

§ Increases soil moisture

§ Riparian forests (associated with rivers)

§ Nutrients go downstream

§ Seed dispersal

§ Rhizome dispersal

○ Negative impacts on terrestrial ecosystems:

§ Respiration

§ Evaporation of nutrients

§ Toxins come through

§ Sediments

§ Root exposure

- Other:

○ Avalanches:

§ Happen year after year in the same place

○ Landslides

○ Volcanism:

§ Tephra - gjóska

○ Pathogens:

§ Disease/insect infestation

○ Humankind:

§ Can be localised or global:

□ T.d. polluted river/climate change

Marine distubance factors:

○ Sub marine landslides

○ Volcanism

○ Erosion & sedimentation

○ Climate:

§ Temperature changes in the stream

§ Salination

○ Pathogens

○ Humankind:

§ Undersea mining

§ Trolling

pollution