COMMUNITY CHANGE (SUCCESSION)

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COMMUNITY CHANGE (SUCCESSION)

• Krebs cpt. 21 pages 403-424 431

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SUCCESSION . Is the non-seasonal, directional
and continuous pattern of colonization and
extinction on a site by populations. Is the
replacement of one kind of community by another
kind the progressive changes in vegetation and
animal life that may culminate in the climax
community (Krebs 622)
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PRIMARY SUCCESSION . recovery from a new
sterile area that has been uncovered by a
retreating glacier, or created by an erupting
volcano. SECONDARY SUCCESSION . recovery of
a disturbed site.
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PRIMARY SUCCESSION
Mt. St. Helens pp403-405
Lake Michigan dunes pp416-419
Glacier Bay pp413-416
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Ice recession in Glacier Bay, Alaska, since 1760
1940
1860
Krebs Fig. 21.7 p414
1760
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SECONDARY SUCCESSION
Krebs pp419-422
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From Drury and Nisbet 1973 Succession can be
considered as an expression of differences in
colonizing ability, growth and survival of
organisms adapted to a particular set of
conditions on an environmental gradient.  The
replacement of one of several species or groups
of species by others results from interspecific
competition and the interactions of herbivores,
predators, and disease which permit one group
plants to suppress slower-growing or less
tolerant ones.
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SUCCESSION PATHWAYS (HENRY HORN)
1. OBLIGATORY SUCCESSION
A
B
C
D
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1. OBLIGATORY SUCCESSION
2. CHRONIC, PATCHY DISTURBANCE

A
B
C
D
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1. OBLIGATORY SUCCESSION
2. CHRONIC, PATCHY DISTURBANCE
3. COMPETITIVE HIERARCHY

A
B
C
D
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1. OBLIGATORY SUCCESSION
2. CHRONIC, PATCHY DISTURBANCE
3. COMPETITIVE HIERARCHY
4. QUASI-REALITY

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Institute Woods, Princeton, N.J. (Henry
Horn) Eastern deciduous hardwood forests
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Grey Birch, Betula populifera
Black Gum, Nyssa sylvatica
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Beech, Fagus sylvatica
Red Maple, Acer rubrum
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4. QUASI-REALITY
BLACK GUM
RED MAPLE
GRAY BIRCH
BEECH
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4. QUASI-REALITY
BLACK GUM
RED MAPLE
GRAY BIRCH
BEECH
BLACK GUM
RED MAPLE
GRAY BIRCH
BEECH
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4. QUASI-REALITY
BLACK GUM
RED MAPLE
GRAY BIRCH
BEECH
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Values in cells are percentages, and represent
the probability ( probability) that any
particular individual tree living now will be
replaced by any other individual tree 50 years
from now. e.g. out of every 100 individuals of
grey birch now living, in 50 years, 36 of those
grey birch will have died and will have been
replaced by black gum.
No. of individuals IN 50 YEARS GRAY BIRCH BLACK GUM RED MAPLE BEECH
No. of individuals NOW GRAY BIRCH BLACK GUM RED MAPLE BEECH
GRAY BIRCH 5 36 50 9
BLACK GUM 1 57 25 17
RED MAPLE - 14 55 31
BEECH - 1 3 96
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FOR EXAMPLE The number of Red Maple and 50
years will be 50 Gray Birch (now) 25 Black Gum
(now) 55 Red Maple (now) 3 Beech (now)
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The predicted percentage composition of a forest
consisting initially of 100 Grey Birch.
Age of forest (yrs) Now 50 100 150 200 ? Data from old forest
GRAY BIRCH 100 5 1 0 0 0 0
BLACK GUM 0 36 29 23 18 5 3
RED MAPLE 0 50 39 30 24 9 4
BEECH 0 9 31 47 58 86 93
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• From Connell and Slatyer 1977
• FACILITATION
• TOLERANCE (COMPETITION)
• INHIBITION

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FACILITATION later stages depend upon
early-stage species to prepare a favorable
environment for them
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TOLERANCElater successional species tolerate
lower resource levels i.e. have lower R than
earlier occupants, and can invade and displace
them by reducing resources to levels below those
tolerated by earlier occupants
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TOLERANCElater successional species tolerate
lower resource levels i.e. have lower R than
earlier occupants, and can invade and displace
them by reducing resources to levels below those
tolerated by earlier occupants i.e. the community
is composed of those species most efficient at
exploiting resources
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INHIBITIONall species resist the invasion of
competitors and are displaced only by death, or
damage by factors other than competition.
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INHIBITIONall species resist the invasion of
competitors and are displaced only by death, or
damage by factors other than competition. i.e.
colonizers will hold a side against all comers
until death
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FACILITATION
TOLERANCE
INHIBITION
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A study from abandoned farmland illustrates some
aspects of Facilitation, Tolerance and Inhibition
(see Krebs pp496-498)

• FIELD ABANDONED IN FALL
• 1. INITIAL INVASION
• Horseweed
• a winter annual
• produces abundant seed
• self-allelopathic

Conyza canadensis
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• 2. NEXT SEASON
• Asters
• More susceptible to decaying roots of horseweed,
  than horseweed
• Tolerant of dry conditions

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• 3. SECOND AND THIRD SEASONS
• Bluestem
• Seedlings invading since initial abandonment
• Broomsedge
• Seedlings invading since initial abandonment
• More tolerant of dry conditions than Asters
• Decaying roots of Horseweed promote growth

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Bluestem
Broomsedge
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SUMMARY

• FACILITATION
• Broomsedge promoted by decaying root
• TOLERANCE
• Broomsedge displaces Aster through competition
  for water
• INHIBITION
• Horseweed seedlings more tolerant of horseweed
  decomposition than Asters

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THE RESOURCE RATIO HYPOTHESIS OF PLANT
SUCCESSION
David TILMAN
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TILMAN, D. 1985. The resource-ratio hypothesis
of plant succession.American Naturalist
125827-852
READING FOR THESE LECTURES Krebs selections
from pp. 182-186
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Resource Ratio Hypothesis

• One species and one resource
• One species and two resource
• Two species and two resources
• Multiple species and two resources

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Resource Ratio Hypothesis

• One species and one resource
• One species and two resource
• Two species and two resources
• Multiple species and two resources

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Resource Ratio Hypothesis

• One species and one resource
• One species and two resource
• Two species and two resources
• Multiple species and two resources

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Resource Ratio Hypothesis

• One species and one resource
• One species and two resource
• Two species and two resources
• Multiple species and two resources

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Resource Ratio Hypothesis

• One species and one resource
• One species and two resource
• Two species and two resources
• Multiple species and two resources

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Species A
birth
Population growth death rate
mortality
0 1 2 3 4 5 6
7 8 9 10
R
Resource level 1
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OPTIMAL FORAGING Any (plant) species will absorb
resources in the proportion by which it is
equally limited by them. This proportion is the
ratio of the two values of R R the
Requirement Value i.e. the level of resource
required to hold a population (of a species) at
equilibrium i.e. where birth rate death rate
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OPTIMAL FORAGING Any (plant) species will absorb
resources in the proportion by which it is
equally limited by them. This proportion is the
ratio of the two values of R R the
Requirement Value i.e. the level of resource
required to hold a population (of a species) at
equilibrium i.e. where birth rate death rate
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OPTIMAL FORAGING Any (plant) species will absorb
resources in the proportion by which it is
equally limited by them. This proportion is the
ratio of the two values of R R the
Requirement Value i.e. the level of resource
required to hold a population (of a species) at
equilibrium i.e. where birth rate death rate
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Species A
birth
Population growth death rate
mortality
0 1 2 3 4 5 6
7 8 9 10
R
Resource level 2
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Species B
birth
Population growth death rate
mortality
0 1 2 3 4 5 6
7 8 9 10
R
Resource level 1
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Species B
birth
Population growth death rate
mortality
0 1 2 3 4 5 6
7 8 9 10
R
Resource level 2
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SPECIES A
1
3
Population growth death rate
SPECIES B
2
4
Resource 1
Resource 2
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Resource Ratio Hypothesis

• One species and one resource
• One species and two resource
• Two species and two resources
• Multiple species and two resources

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Species A
8 7 6 5 4 3 2 1
Births A gt Deaths A Population increases
Resource 2
Zero Net Growth Isocline ZNGI Births Deaths
Births A lt Deaths A Population declines
0 1 2 3 4 5 6
7 8 9 10
Resource 1
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Species B
8 7 6 5 4 3 2 1
Births B gt Deaths B Population increases
Resource 2
Zero Net Growth Isocline ZNGI Births Deaths
Births B lt Deaths B Population declines
0 1 2 3 4 5 6
7 8 9 10
Resource 1
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Resource Ratio Hypothesis

• One species and one resource
• One species and two resource
• Two species and two resources
• Multiple species and two resources

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Species A and B
8 7 6 5 4 3 2 1
Resource 2
ZNGI A
ZNGI B
0 1 2 3 4 5 6
7 8 9 10
Resource 1
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A
B
8 7 6 5 4 3 2 1
Resource 2
ZNGI A
ZNGI B
0 1 2 3 4 5 6
7 8 9 10
Resource 1
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A B
8 7 6 5 4 3 2 1
Both species can grow
A wins
Resource 2
ZNGI A ZNGI B
B wins
Neither species can survive
0 1 2 3 4 5 6
7 8 9 10
Resource 1
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A B
8 7 6 5 4 3 2 1
Resource 2
ZNGI A ZNGI B
0 1 2 3 4 5 6
7 8 9 10
Resource 1
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A B
8 7 6 5 4 3 2 1
A B coexist
A wins
Resource 2
ZNGI A ZNGI B
B wins
Neither species can survive
0 1 2 3 4 5 6
7 8 9 10
Resource 1
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A B
8 7 6 5 4 3 2 1
A B coexist
A wins
WHY?
Resource 2
ZNGI A ZNGI B
B wins
Neither species can survive
0 1 2 3 4 5 6
7 8 9 10
Resource 1
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A B
8 7 6 5 4 3 2 1
Resource 2
ZNGI A ZNGI B
0 1 2 3 4 5 6
7 8 9 10
Resource 1
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A B
8 7 6 5 4 3 2 1
Resource 2
ZNGI A ZNGI B
0 1 2 3 4 5 6
7 8 9 10
Resource 1
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Resource Ratio Hypothesis

• One species and one resource
• One species and two resource
• Two species and two resources
• Multiple species and two resources

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A B C D E
8 7 6 5 4 3 2 1
Resource 2
A
B
C
D
E
0 1 2 3 4 5 6
7 8 9 10
Resource 1
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A B C D E
8 7 6 5 4 3 2 1
A
AB
B
BC
C
CD
Resource 2
D
A
DE
B
C
None
D
E
E
0 1 2 3 4 5 6
7 8 9 10
Resource 1
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Random Resource Supply
A B C D E
8 7 6 5 4 3 2 1
A
AB
B
BC
C
CD
Resource 2
D
A
DE
B
C
None
D
E
E
0 1 2 3 4 5 6
7 8 9 10
Resource 1
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Positively Correlated Resources
A B C D E
8 7 6 5 4 3 2 1
A
AB
B
BC
C
CD
Resource 2
D
A
DE
B
C
None
D
E
E
0 1 2 3 4 5 6
7 8 9 10
Resource 1
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Negatively Correlated Resources
A B C D E
8 7 6 5 4 3 2 1
A
AB
B
BC
C
CD
Resource 2
D
A
DE
B
C
None
D
E
E
0 1 2 3 4 5 6
7 8 9 10
Resource 1
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PRIMARY SUCCESSION
A B C D E
8 7 6 5 4 3 2 1
A
AB
B
BC
C
CD
Resource Light
D
A
DE
B
C
D
E
E
0 1 2 3 4 5 6
7 8 9 10
Resource Nitrogen
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SECONDARY SUCCESSION
A B C D E
8 7 6 5 4 3 2 1
A
AB
B
BC
Poor soil
Rich soil
C
CD
Resource Light
D
A
DE
B
C
D
E
E
0 1 2 3 4 5 6
7 8 9 10
Resource Nitrogen
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Black Oak Aspen
8 7 6 5 4 3 2 1
Aspen
Black Oak
Red Oak Black Oak
Red Oak
White Oak Red Oak
Resource Light
White Oak
Sugar Maple White Oak
Sugar Maple
0 1 2 3 4 5 6
7 8 9 10
Resource Nitrogen
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DIVERSITY
A B C D E
8 7 6 5 4 3 2 1
1
2
Resource Light
A
B
4
C
D
0
E
0 1 2 3 4 5 6
7 8 9 10
Resource Nitrogen
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TILMAN THE END
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• FORCIER, Keith
• Studied trees in a New Hampshire forest
• Trees with dbh lt2 cm (400 plots)
• 90 of canopy
• Sugar maple
• American beech
• Yellow birch

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SPECIES Density (/m2) (dmin/dmax ) x 100 plots with at least 1 seedling Mass/ind (mg)
Yellow birch 21.3 2 92 8
Sugar maple 10 57 73 268
Beech 3.9 66 55 569
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Number of cohort alive at beginning of interval Number of cohort alive at beginning of interval Number of cohort alive at beginning of interval
Age interval Yellow birch Sugar maple Beech
0-1 1-2 2-3 3-4 4-5 5-6 6-7 7-8 8-9 9-10 1000 70 lt30 1000 583 317 225 166 118 84 54 48 42 1000 410 262 188 138 121 110 92 87 83
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CANOPY SEEDLINGS SEEDLINGS SAPLINGS
lt 0.5m tall lt 0.5m tall 0.5 2 m tall
Yellow birch Yellow birch Sugar maple Beech 0 - -
Sugar maple Yellow birch Sugar maple Beech 0 0 0
Beech Yellow birch Sugar maple Beech 0 0 0 0 Seed - Sprouts
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CLIMAX MICROSUCCESSION
Beech (seed)
Beech (sprouts)
MINOR DISTURBANCE
Sugar Maple
Yellow birch
CATASTROPHIC DISTURBANCE
Successional communities
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