Predict how would the forest look in ten years if it were left undisturbed 62Ecological Disturbances and Succession SC912L174 Describe changes in ecosystems resulting from seasonal variations climate change and succession ID: 713548
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Slide1
Do Now: Fire as an Ecological Disturbance
Predict how would the forest look in ten years if it were left undisturbed. Slide2
6.2_Ecological Disturbances and Succession
SC.912.L.17.4 Describe changes in ecosystems resulting from seasonal variations, climate change and succession.By Dr. Suris SotoSlide3
What Is Disturbance?
A disturbanceIs an event that changes a community (both biotic and abiotic are affected)Removes organisms from a community
Alters resource
availabilitySlide4
Causes of Disturbances
Natural Human
They are common in
ecosystems
Seasonal Variations (summer, fall, winter, spring)
Fire
Hurricanes
Floods
Volcanic Eruptions
Are the most widespread agents of disturbance
Usually reduces species diversity
Humans also prevent some naturally occurring disturbances
Deforestation and land cleared
Farming
Urbanization (Developments)Slide5
Ecological Succession
Ecological successionIs the gradual sequence of community and ecosystem changes
after a disturbance
One community of organisms
replaces
anotherSlide6
Types of Ecological Succession:
Primary successionOccurs where no soil, (barren terrain)
exists when succession begins
No pre-existing plant or animal life
Examples: After volcanic eruption, retreating glacier (natural), abandon parking lot (human-caused)
Secondary succession
Begins in an area where
soil remains
after a disturbance
Some organisms may still be there
Examples: After a flood, hurricane, tornado (natural) or after
land cleared for farming, deforestation (human-caused)Slide7
Examples of Primary Succession ---- No Soil, barren rock
Glacier Retreating
Volcanic Eruption
Abandon parking lotSlide8
Examples of Secondary succession
Secondary Succession after a fireA FireIs a significant disturbance in most terrestrial ecosystems
Is often a necessity in some communities (helps recycle materials)
(a)
Before a controlled burn.
A prairie that has not burned for
several years has a high propor-
tion of detritus (dead grass).
(b)
During the burn.
The detritus
serves as fuel for fires.
(c)
After the burn.
Approximately one month after the controlled burn, virtually all of the biomass in this prairie is living.
Figure a–cSlide9
The large-scale fire in Yellowstone National Park in 1988Demonstrated that communities can often respond very rapidly to a massive disturbance
Figure 53.22a, b
(a) Soon after fire.
As this photo taken soon after the fire shows, the burn left a patchy landscape. Note the unburned trees in the distance.
(b) One year after fire.
This photo of the same general area taken the following year indicates how rapidly the community began to recover. A variety of herbaceous plants, different from those in the former forest, cover the ground.Slide10
Secondary Succession See how after a disturbance, a community is replaced by another
Notice how both the biotic and abiotic factors may change Example: as the trees grow taller (biotic), they cast a shade (light= abiotic) over the smaller tressSlide11
Pioneer species
Always the first species to move into a devastated areaMust be able to live on limited resourcesMust be able to live in barren rockThey include
Bacteria
Lichens
Lichens are a symbiosis (close relationship) of a fungus and a green algae
Each organisms depends on each other for survival (mutualism)
Fungus anchors lichen to a surface, absorbs water and nutrients, and protects the algae from direct sunlight.
The algae performs photosynthesis to make its own food and also feed the fungus
As lichens grow, they make break down rock , help form soil. When it dies it decomposes enriching the soil. Slide12
Pioneer species (Primary Succession) Lichens
Mosses
Bacteria Slide13
Primary Succession Slide14Slide15
Climax community Fairly stable community
Marks the end of succession in an area Organisms present depend on the climate and physical features of the areaEx. In areas with little rain the climax is a grasslandNothing lasts forever: A new disturbance can happen at any time
Disturbances in climax communities can lead to secondary succession (fire, drought, snow) or primary succession in the event of volcanic eruption covering the soil with lava, hardened to rock, etc. Slide16
Draw it yourself:
Illustrate one
of the two types of ecological succession.
Describe the events that take place
step by step
.
List the organisms that colonize the area
Include the biotic or abiotic conditions that change over time that led to the colonization of the area by such organisms.
Example: As the shrubs grow taller, they shade the grasses, so these dye due to the lack of sunlight.Slide17
Sample work:
Descriptions and explanations will go on the back of the paper in a series of steps. Slide18
Which of the following is not a possible cause of secondary succession?
FireFloodEarthquake
Change of seasonsSlide19
Which of the following is an example of primary succession?
Lichens growing on rocks after a volcanic eruptionGrasses growing after a forest fireOak trees replacing pine trees in a forest
Nonnative species introduced into a climax communitySlide20
Which term refers to final forest’s development?
Pioneer forestSecondary forestClimax forest
Conifer forest