Transcript Ecosystem Restoration

Ecosystem Restoration
Repaying the Ecological Debt
Conceptual issues
After manipulation of a natural system,
have three choices:
Ecosystem Restoration
Restoration – bring back to pre-disturbance
condition
Rehabilitation – partial replacement of original
ecosystem
Enhancement – alternative ecosystem
Note: to understand above scenarios of recovery
have to consider two biological factors of
colonization and succession
Colonization and Succession
- Both are ecosystem changes with time
1.
Colonization – arrival of new species in an
empty patch
Colonization of “bare” areas based on MacArthur
and Wilson theory of island biogeography 
CONSIDER DENUDED PATCHES AS ISLANDS
Ex. Clear-cuts, strip mine are islands in a “sea” of
mixed deciduous forest
Seq
Species (s)
S = Seq (1-e -Gt)
∆S = colonization rate
G = ____
∆t
Time (t)
1. Number of species depends on colonization rate (G)
2. G starts out high, gets smaller and smaller
3. Colonization rate based on two relationships
(mainland, deciduous forest)
Species source
inhospitable terrain
“islands”
(clear-cut, toxic waste
site, strip mine)
▲ Longer distance from source (mainland) = lower # of species
inhospitable
terrain
Larger patches = higher probability of being “hit” by propagules
▲ Increased size/area = increased # of species on islands
Seq
Factors Affecting Colonization Rates
Immigration
Extinction
Proximity to source
Residual disturbance, toxics
Kind of organism (vagility)
Competition
Reproductive rate (r- vs Kselection)
Habitat diversity and quality
Air, water currents (rafting)
Generalist/Specialist
Note: once reach equilibrium  dynamics become interactive = succession
Non-interactive
Interactive = succession
Species (s)
Seq
Time (t)
Succession
• Orderly change in community composition over
time
• Usually follows colonization  especially studied
in plant communities
• Two models
– relay floristics
– initial floristics
Abandonment
Weeds |
Grassland
Species
Crop
Relay floristics
Years
|
Shrubland
|
Forest
Abandonment
Weeds |
Grassland
Species
Crop
Initial floristics
Years
|
Shrubland
|
Forest
Implications for Reserve Design
better
worse
A
B
C
D
E
F
Significance to restoration
of altered ecosystems
• Relay floristics – ongoing process based on
external input
• Initial floristics – happens all at once based on
internal input
▲Might have to manage system to help recovery
- stock fish
- soil stabilization with annual plants
- etc.
Tionesta
Natural
Area,
Allegheny
National
Forest, PA
Photo by R. Grippo