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Fundamental Degradation Terminology. NREM 612. high. Initial state. Function. Degr. state. low. low. high. Structure. I. Ecosystem Stability. Ecosystem stability is primarily a function of: Sensitivity & Resilience to change. - PowerPoint PPT Presentation
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Fundamental Degradation Terminology
NREM 612
StructureF
unct
ion
Initial state
Degr. state
low highlo
whi
gh
2
I. Ecosystem Stability
Ecosystem stability is primarily a function of:Sensitivity & Resilience
to change.
A. Sensitivity – defined as (in Barrow 1991) “the degree to which a given environment undergoes change due to natural forces, human action, or a combination of both.”
B. Resilience – defined as (in Barrow 1991) “ the way in which the ecosystem can withstand use.”
C. Matrix of sensitivity and resilience can form the basis for land classification (Blaikie & Brookfield 1987)
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SensitivityResilience High Low
High
Low
SensitivityResilience High Low
High easy to degradeeasy to restore
Low
Think of ecosystems that would fit into each quadrat the matrix?
With a partner, fill in the tables below
hard to degradeeasy to restore
easy to degradehard to restore
hard to degradehard to restore
Sensitivity & Resilience Matrix
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SensitivityResilience High Low
High Mangrove Tidal salt marsh
Temperate forest
Low Tropical rain forestDry forestCoral reef
Herbaceous wetlandRangeland
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Stability Terminology
II. Stability terminology
A. General1. Constancy: lack of variation in some property of a system, ability of pop. to preserve its #s
2. Persistence: survival time of a system or come component of a system
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B. Terms to evaluate response to disturbance:
1. Resistance: ability to resist displacement from initial state, syn. w/ inertia
2. Resilience: ability to recover to an initial state after disturbance
3. Elasticity: speed of recovery to initial state after disturbance
4. Hysteresis: path of recovery differs from path of degradation (process or time)
5. Malleability: degree to which post-disturbance state differs from initial state
Illustrate terms in figure below:
StructureF
unct
ion
Initial state
Degr. state
new. state
low high
low
high
Stability Terminology, con’t
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II. Succession1. From Barrow 1991: “An ecosystem returns to a climax state via a series of successional stages – which are equilibrium points reached after disturbance
A. Primary succession – establishment of plants and an
ecosystem on land not previously vegetated
“from scratch”
B. Secondary succession – recolonization of previously
vegetated land following disturbance, soil remains
intact
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2. r-selected species: early-successional, adapted to disturbance, good dispersal capabilities, large #s of offspring, generalist, shorter lifespan
3. k-selected species: later-successional, better competitors, smaller # of offspring w/ higher survival rates, specialist, longer lifespan
Succession, con’t
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4. Facilitation: early successional spp. alter env. to make it more favorable for estab. of later-successional spp.
5. Inhibition: early successional spp. alter env. to make it less favorable to estab. of later-successional spp.
6. Tolerance: early spp. neither help nor hinder later spp.
Succession, con’t
StructureF
unct
ion
Initial state
Degr. state
new. state
low high
low
high
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Relationship between stability and diversityAre diverse systems more stable than simple systems?
Pimm et al. (1995)?
III. Stability-Diversity Relationship
A. Species Richness: # of different species in a particular area
B. Evenness: relative abundance of each species represented in a particular area
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Q: Which site has greater evenness?
Site 1 Site 2
Q: What is the species richness (SR) for site 1 & site 2?
SR for site 1 & 2 = 4
Site 1 = high Site 2 = low
Q: Which site do you consider more diverse?
Site 1
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C. Diversity: not just richness or abundance, but relationship between richness & abundance
Define these terms quantitatively:
s = # of species
Pi = proportion of individuals belonging to ith species
Diversity
sShannon’s Diversity Index = H’ = - Pi * lnPi
i=1
H’ ranges from ~ 1 – 3.5, usu. not > 4.5
Evenness = E = H’ ln(s)
E ranges from 0-1
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Example calculation: How to calculate H’ & E given data
Site 1 Site 2
sH’ = - Pi * lnPi
i=1
E = H’
ln(s)
Species
ni
Pi
lnPi
Pi*lnPi
Species
ni
Pi
lnPi
Pi*lnPi
E= E=
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Q: Relationship between stability and diversityAre diverse systems more stable than simple systems?
Pimm et al. (1995)?
Stability-Diversity Relationship
1. Species Diversity:
Eveness, richness, H’, etc.
2. Functional Diversity:The range and value of traits that influences ecosystem functioning; “the component
of diversity that influences ecosystem dynamics, stability, productivity, nutrient balance, and other aspects of ecosystem functioning” from Tilman, D. 2001
“Functional Diversity” in the Dictionary of Biodiversity
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Additional Materials
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D. Successional Theories
1. Clementian: holistic approach, sees succession as orderly, directional, predictable, system proceeds towards stable climax community
a. autogenic-internal
A B C D
F. Clements
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2. Gleasonian: individualistic approach, sees succession as disorderly, stochastic, unpredictable, determined by chance events, no climax community
b. allogenic-external
B
A D
C
H. Gleason
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Which theory is correct?
Relationship of succession with stability?
Relationship w/ current restoration practices?
Neither, examples for which each theory works
Gleasonian probably closer to reality than Clementian
Clements argue that climax community = evidence of stability
Gleason would discount stability altogether
Self-design – Clementian
Designer theory - Gleasonian
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II. Sustainability Terminology
A. Basic Definitions
1. Primary (1o) Productivity: increase in biomass of green plants over a given period
2. Sustainable Yield: fraction of net 1o prod removed on a continuous basis w/o destroying/ 1o prod
3. Carrying Capacity: max. # of individuals supported by a given env.
4. Sustainable Development (SD): Any activity that raises social welfare w/ maximum amount
of resource conservation & minimum amount of environ. degr. allowable w/i given econ, social, technical constraints
a. Implies anticipate & avoid rather than react & cure mentality
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a. Alpha (α) Div: w/i site or habitat
b. Beta (β) Div: from site to site or along transect, gradient
c. Gamma (γ) Div: diversity of a larger geographical unit, i.e. landscape or region; γ div. = (α & β)
Which site has highest α diversity?
Which region has highest β diversity?
Which region has highest γ diversity?
Sites 1 & 3
Region Y, higher species turnover
Region Y w/ higher total # of species