ENVS 3710 Lecture Notes - Lecture 6: Secondary Succession, Ecotone, Monarch Butterfly

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Published on 13 Apr 2013
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Successional dynamics in relation to landscape ecosystems
- Succession bad rep in the 50s and 60s to deterministic of its use
o Locked into the use of the deterministic process
o Succession and dynamics used interchangablely
Succession (ecological community dynamics) in its broadest most comprehensive sense is the gradual
replacement of one community of organism in an ecosystem by another
- Gradual process not aware that it is occurring
- Within a particular ecosystem
- Not fully understood why it happens; but it occurs over and over again in ecosystems
There are two broadly recognized types of succession: primary and secondary. Primary succession
involves gradual community change on larger extents of land that has been newly created (lava flows)or
newly exposed (glacial tills or landslides)
- Things that happen in primary also happen in the secondary
- A sort of “hybrid succession
- Gap phase succession a micro succession (occurs on a very small piece of land); variant of
second type of succession
- Primary succession devolved of life; or newly created; single cell organisms that could stay
underground for a long period of time
Secondary secession occurs where the standing vegetation has been removed over an extensive area by
major or catastrophic disturbances (fire, agriculture, mining, flood etc.)
- All natural: fire and flooding - catastrophic
- Human intervention: fire (aboriginal- traditional firing of the forests) and mining
- Disturbances of ecosystems fire and agriculture
The dynamic process by which community change occurs is highly site and context specific, and will not
occur exactly the same even on very similar sites in the same region
- Not 100% understood why the species change
- Many factors has effect on how succession occurs how plants replace the next one
- The context is also important what is on it? What causes it to change? And time (directional
flow)? unfolding into the future; the memory (the site holds all that it has been)
Secondary succession in particular will depend on the history of what has been on the site in terms of
ecosystems prior to the major or catastrophic disturbances, and the history of the types, intensities,
frequencies and extents of prior disturbances.
- Past disturbances are important; type of disturbances
- How much of the land was affected would be in the history of the land
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- Would play out after the last disturbances it had on the land previous landscape disasters
might be important to the landscape of the “NOW”
Secondary succession will also depend on what ecological systems exist as context to the site
undergoing secondary succession, their sizes, configurations and conditions.
- If abandon; it would be a different succession vs. a desert and a lake on either side of the
succession
- Context is not as important in the first 5 10 years, the most important is the memory of what
has been grown on it
Secondary succession has been intensely studied in ecosystems with little human intervention. In human
altered ecosystems, successional processes unfold as much in elation of human use of the land as on
natural processes of community change.
IMG: parking lot abandoned for 20 years (grass and trees started to grow) primary succession
o Soil underneath would harbor some seeds before the contraction took place
o Start to pop up in the crakes below
o Forces it to follow a slower succession process for secondary
Because successional process are highly site and context specific and each site has unique history, the
pattern of community change will be variable. However, there are trends, or trajectories of change
which can be very broadly understood.
- One general plant community (would be replaced by another) and another
- Trajectory size, species type
The classic example of a secondary successional trajectory is the abandoned pasture field changing to
forest
- Trajectory might be the same but the species might not be the same
IMG: abandon pastures
In broad outline old field succession proceeds slowly through arguable six or seven discernibly
communities of organism: old field to perennial forbs and grasses to short lived shrubs and trees to
longer lived shrubs and trees to very long lived trees and shrubs. Forbs of different plant species and
attendant herbivores, carnivores and soil biota all change as the larger vegetated community changes
- Annually or bi annually species would dominate
- After 3 years plants (perennials) longer lived (3 7 or 8 years)
- The plants that you would see are : Seeds within the soil (since the last time the ground was
disturbed) or
- Herbaceous plants stay there for about 15 years (might come after community and
community)
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Document Summary

Succession bad rep in the 50s and 60s to deterministic of its use: locked into the use of the deterministic process, succession and dynamics used interchangablely. Succession (ecological community dynamics) in its broadest most comprehensive sense is the gradual replacement of one community of organism in an ecosystem by another. Gradual process not aware that it is occurring. Not fully understood why it happens; but it occurs over and over again in ecosystems. There are two broadly recognized types of succession: primary and secondary. Primary succession involves gradual community change on larger extents of land that has been newly created (lava flows)or newly exposed (glacial tills or landslides) Things that happen in primary also happen in the secondary. Gap phase succession a micro succession (occurs on a very small piece of land); variant of second type of succession. Primary succession devolved of life; or newly created; single cell organisms that could stay underground for a long period of time.

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