Welcome! §Please read the board completely. §Please get out your Ecology objectives #1- 5 and...
-
Upload
marvin-booker -
Category
Documents
-
view
217 -
download
1
Transcript of Welcome! §Please read the board completely. §Please get out your Ecology objectives #1- 5 and...
Welcome!
Please read the board completely.
Please get out your Ecology objectives #1-5 and review with your neighbor for the quiz. (add review ideas in a different color!)
Succession – Change in Ecosystems
Case Study: Enchanted Rock, TX
Enchanted Rock, State Park
15 mi NW of Fredricksberg
Granite batholith surrounded by limestone
.Succession: the orderly replacement of one ecosystem by another.
Primary Succession Secondary Succession
Primary succession begins with bare rock.
The granite rock cracks and breaks off as it is heated and cooled each day and season. This is the first step in the formation of soil.
Dust, rain, and soil particles are trapped in the depressions, allowing grasses to grow. The first species to appear in an
area are referred to as pioneer species.
Characteristics of early successional or pioneer plants:
Grow close to ground
reproduce quickly
can survive harsh conditions
short lives
Plants live, die and are decomposed, adding to the soil depth. This allows more seeds to germinate and grow.
Cacti can grow here, too and are a good example of midsuccessional species.
As communities grow, abiotic conditions are altered,
allowing new communities to take hold.
How would soil development change the amount of moisture available to plants? How would the growth of plants change the amount of wind at ground level?
Climax communities represent the final stage of succession. These climax communities will remain in this spot until they are disrupted.
Characteristics of climax or late successional communities
Slow growingcan tolerate shadetall (or at least taller than pioneers)
Climax communities differ by ecoregion, but they generally include long-lived and woody species.
Climax communities are described by their vegetation, but remember that animal communities will change as succession proceeds, too.
Factors affecting succession patterns and rates
Facilitation – one species makes an area suitable for species with
different requirements.
Inhibition – early species hinder the establishment and growth of
other species
Tolerance – late successional plants are largely unaffected by
plants at earlier stages of succession
Secondary Succession begins with a disturbance in an existing ecosystem.
Clear cuttingAbandoned agricultural fieldFire!
Some Climax species are fire adapted!
Humans don’t like disturbances, but some ecosystems need them!
Fire wars – 17-31
What can you add now?
Primary succession Secondary succession
Fire is critical to prairie and forest ecosystems
Returns nutrients to soil Helps certain seeds
germinate Forest – clears underbrush
/fuel Prairie – kills trees Light can reach soil Help control
pathogens/insects
Intermediate Disturbance hypothesis
Fire Suppression
1944 – US Forest Service
1988 – fires in Yellowstone shocked nation
1990 – fire policy change
Yellowstone 1988 1.4 million acres burned; May - Nov
US Forest fire policy
Extinguish arsonManage lightning strikesProtect peopleApplication of improved scientific
understanding in succession
Succession is a pattern
Nature doesn’t always fit human categories
Many scientists doubt the usefulness of the concept of succession
Succession does help predict what changes may occur in an ecosystem over time