Biol 302 succession 1

COMMUNITY CHANGE COMMUNITY CHANGE (SUCCESSION)(SUCCESSION)

Krebs cpt. 21; pages 403-424; 431Krebs cpt. 21; pages 403-424; 431

Biol 302 succession 2

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)

Biol 302 succession 3

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.

Biol 302 succession 4

PRIMARY SUCCESSION

Mt. St. Helens pp403-405

Lake Michigan dunes pp416-419

Glacier Bay pp413-416

Biol 302 succession 5

SECONDARY SUCCESSION

Krebs pp419-422

Biol 302 succession 6

Connell and SlatyerConnell and Slatyer 19771977

Succession driven by interactions Succession driven by interactions between species:between species:

FACILITATIONFACILITATION

TOLERANCE (COMPETITION)TOLERANCE (COMPETITION)

INHIBITIONINHIBITION

Biol 302 succession 7

FACILITATION …only certain pioneer species can establish after disturbance. Early species enhance the ability of later species to establish.

INHIBITION …any species can invade. Once established, species resist further invasion and are displaced only by death or further disturbance.

TOLERANCE …any species can invade. Early species have little or no effect on abilities of later species to invade. Later species can displace early species by reducing resources to levels below those tolerated by earlier occupants.

Biol 302 succession 8

Facilitation

SUCCESSION PATHWAYSSUCCESSION PATHWAYS

A B C D

A B

CD

Tolerance & Inhibition

Biol 302 succession 9

Biol 302 succession 10

FACILITATION

TOLERANCE INHIBITION

Biol 302 succession 11

A study from abandoned farmland illustrates A study from abandoned farmland illustrates some aspects of Facilitation, Tolerance and some aspects of Facilitation, Tolerance and

Inhibition (see Krebs pp 419-422) Inhibition (see Krebs pp 419-422)

FIELD ABANDONED IN FALLFIELD ABANDONED IN FALL

1. INITIAL INVASION:1. INITIAL INVASION:

• HorseweedHorseweed

• a winter annuala winter annual

• produces abundant seedproduces abundant seed

• self-allelopathicself-allelopathic Conyza canadensis

Biol 302 succession 12

2. NEXT SEASON:2. NEXT SEASON:

• Asters Asters

• More susceptible to More susceptible to decaying roots of decaying roots of horseweed, than horseweedhorseweed, than horseweed

• Tolerant of dry conditionsTolerant of dry conditions

Biol 302 succession 13

3. SECOND AND THIRD SEASONS3. SECOND AND THIRD SEASONS:

• BluestemBluestem

• Seedlings invading since initial abandonmentSeedlings invading since initial abandonment

• BroomsedgeBroomsedge

• Seedlings invading since initial abandonmentSeedlings invading since initial abandonment

• More tolerant of dry conditions than AstersMore tolerant of dry conditions than Asters

• Decaying roots of Horseweed promote growthDecaying roots of Horseweed promote growth

Biol 302 succession 14

Bluestem

Broomsedge

Biol 302 succession 15

FACILITATION:

• Broomsedge is promoted by decaying roots of horseweed & aster

TOLERANCE:

• Broomsedge displaces aster through competition for water

INHIBITION:

• Horseweed litter prevents aster from persisting

SUMMARYSUMMARY

Biol 302 succession 16

FORCIER 1975

Succession driven by interaction of disturbance & life history traits of species

Studied trees in a New Hampshire forest

• Trees with dbh >2 cm (400 plots)

• 90% of canopy:

• Sugar maple

• American beech

• Yellow birch

Biol 302 succession 17

Eastern deciduous hardwood forests

Several tree species

Biol 302 succession 18

Grey Birch, Betula populifera

Black Gum, Nyssa sylvatica

Biol 302 succession 19

Red Maple, Acer rubrum

Beech, Fagus sylvatica

Biol 302 succession 20

YELLOW BIRCH

SUGAR MAPLE BEECH

r K

Biol 302 succession 21

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

Biol 302 succession 22

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

<30

1000

583

317

225

166

118

84

54

48

42

1000

410

262

188

138

121

110

92

87

83

Biol 302 succession 23

CANOPY SEEDLINGS SAPLINGS

< 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 +

Biol 302 succession 24

CATASTROPHIC DISTURBANCE

Yellow birch

Sugar Maple

Beech (seed)

Beech (sprouts)

MINOR DISTURBANCE

Successional communities