1. COMMUNITY CHANGE (SUCCESSION)
Krebs cpt. 21; pages ; 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. SECONDARY SUCCESSION …. … recovery of a disturbed site.
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 pp
Biol 302 succession
Glacier Bay pp

5. SECONDARY SUCCESSION
Krebs pp
Biol 302 succession

6. Succession driven by interactions between species:
Connell and Slatyer 1977
Succession driven by interactions between species:
FACILITATION
TOLERANCE (COMPETITION)
INHIBITION
Biol 302 succession

7. FACILITATION …only certain pioneer species can establish after disturbance. Early species enhance the ability of later species to establish.
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.
INHIBITION …any species can invade. Once established, species resist further invasion and are displaced only by death or further disturbance.
Biol 302 succession

8. A B D C A B C D SUCCESSION PATHWAYS Facilitation
Tolerance & Inhibition A B D C
Biol 302 succession

9. Biol 302 succession

10. FACILITATION
TOLERANCE
INHIBITION
Biol 302 succession

11. FIELD ABANDONED IN FALL
A study from abandoned farmland illustrates some aspects of Facilitation, Tolerance and Inhibition (see Krebs pp )
FIELD ABANDONED IN FALL
1. INITIAL INVASION:
Horseweed
a winter annual
produces abundant seed
self-allelopathic
Conyza canadensis
Biol 302 succession

12. More susceptible to decaying roots of horseweed, than horseweed
2. NEXT SEASON:
Asters
More susceptible to decaying roots of horseweed, than horseweed
Tolerant of dry conditions
Biol 302 succession

13. 3. SECOND AND THIRD SEASONS: Bluestem
Seedlings invading since initial abandonment
Broomsedge
More tolerant of dry conditions than Asters
Decaying roots of Horseweed promote growth
Biol 302 succession

14. Bluestem
Broomsedge
Biol 302 succession

15. Broomsedge is promoted by decaying roots of horseweed & aster
SUMMARY
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
Biol 302 succession

16. Studied trees in a New Hampshire forest
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. Beech, Fagus sylvatica
Red Maple, Acer rubrum
Biol 302 succession

20. YELLOW BIRCH
SUGAR MAPLE
BEECH
r K
Biol 302 succession

21. % plots with at least 1 seedling
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
583
317
225
166
118 84 54 48 42
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
Sugar maple
Beech +
+ 0 - ++
Seed -
Sprouts +
Biol 302 succession

24. CLIMAX MICROSUCCESSION
Beech (sprouts)
Beech (seed)
MINOR DISTURBANCE
Sugar Maple
Yellow birch
CATASTROPHIC DISTURBANCE
Successional communities
Biol 302 succession