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Unformatted text preview: vironment Clear cutting entire water shed Nutrient losses were 10x higher in clear cut water shed relative to water
shed number 6 Doubled nitrogen fixation rates globally, all not beneficial Disturbance has a negative impact on nutrient cycles
Aldo Leopold (1887-1948)
A Sand County Almanac
“The Odyssey of X” describes how man influences nutrient cycles
Succession (Chp 20)
primary vs secondary
an integrated summary Bacteria fungi and lichens create weathering of rocks to facilitate the initial production of
an area – EX: Glacier Bay Alaska (took 1500 to 2000 years for final stable climax
community to form)
Community organization in space Smaller spaces create more dense communities and inhibit development of the area Look at composition and growth form Special composition based on physionomy
Community organization through time (temporal changes) Herbaceous species give rise to an area that can hold shrubs, which then gives rise to
trees New ground usually have pioneer species, change with site location, but process
remains the same Alaska ecosedum, willowards species then other organisms come in New species modify the environment Suga are in steep slopes Muskegs on shallow
Example of ecological succession in an old field
changing to a pine forest
then a pine forest
then an oak hickory forest
Your text describes ecological succession for:
Glacier Bay, Alaska
A rocky intertidal community
Sycamore Creek, Arizona Do species composition, community structure, and associated ecological processes
change in a predictable, directional way over time in ecological communities?
Succession – a change in species composition and community structure over time
Sere – series of communities
Seral stage – each community
Climax – final “stable” community Most studies of succession focus on plants because plants influence animals
Secondary Succession in Virginia
Pgs 487-488 100-150 years Old field
Grasses and weeds
Loblolly pine forest
Oak forest Loblolly pine forest - No hardwoods
- Recurring fires
- Poor soils Animal succession?
Succession in environments that have not been influenced by organisms. A slow
Examples: Receding glaciers, colcanoes, talus slopes
In Virginia? Accreting coastlines Secondary Succession
Succession after a disturbance in environments where organisms once thrived
Examples: Fire, floods, avalanches, hurricanes, tornadoes, etc.
Human related disturbances?
Agriculture, clearcutting, roadcuts, mining?
TIME! New land
(1^0 Succession) Pioneer seral stage Seral stages CLIMAX Disturbance
Relate these mechanisms to the data presented in Figures 21, 23, 24 and 25
Succession may include a combination of all three of these mechanisms
Stability – the persistence of, or rapid return to, a given state after a temporary
Resistance – to remain unchanged
Resilience – to absorb changes and rapidly return to an original state
STABILITY = RESISTANCE + RESILIENCE System
parameter Disturbance or perturbation...
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- Spring '12