Test 1.3 Ecological Succession

Question 1

What is Ecological Succession?

Answer 1

Non seasonal, continuous pattern of colonization, change & extinction at a site by species populations.

Question 2

Allogenic Succession

Answer 2

Species sequence occurs brought about by abiotic factors e.g: changes to the environment; silk deposition aquatic–> terrestrial environment

Question 3

Autogenic Succession

Answer 3

Species sequence occurs brought about by the organism themselves

Question 4

Degradative Succession

Answer 4

When new and degradable resources are used successively by a number of species. Sequence termites as the resource is used up.

• Salmon left overs from bears
• Fallen pine needles broken down by different fungi

Question 5

Autogenic Succession - Primary succession

Answer 5

Occurs on landforms where no remnants of a previous community exist e.g. lava flows

A makes environment more suitable for B which does the same for C which does the same for D etc…

Question 6

Autogenic Succession - Secondary succession

Answer 6

Occurs in space opened by complete or partial removal of species but where resources remain

Question 7

What is the successional clock?

Answer 7

Stages of succession

Bare ground –> Pioneer seal stage –> Seral stages –> Climax

Question 8

R-selected species

Answer 8

R=RAPID: Species with high growth rates, produce many offspring, exploit less crowded ecological niches

Question 9

K-selected species

Answer 9

Species with populations that fluctuate near the carrying capacity. Found in late successional, stable biological communities

Question 10

Facilitation mechanism of succession

Answer 10

Species help one another to change the environment in ways that aid other species to colonise

e.g. plants following glacial retreat

Question 11

Tolerance mechanism of succession

Answer 11

Species put up with each other but have different competitive abilities

e.g. Old field succession

Question 12

Inhibition mechanism of succession

Answer 12

Opposite to facilitation, the one who gets in first takes over and prevents others getting in

e.g. Seaweed succession on rocky shores - green algae out competes red algae. But red algae tougher therefore remain after heavy storm
Green algae predated by herbivorous crabs

Question 13

Tolerance

Answer 13

A species neither facilitates nor inhibits its would be successors

Question 14

2 Methods of documenting succession

Answer 14

Observe seral stages over time.

Compare communities in space that corresponds to different stages in successional time (Sousa 1979)

Question 15

Old field succession:

Answer 15

• (Bazzaz, 1979) Studied in EUS
• Pre-colonial hardwoods destroyed by farmers
• Farms abandoned as wester frontier opened In 19th century
• Exposed fields colonised by pioneers, regenerative succession occurs

Weeds–> herbaceous perennials–> shrubs–> early successional trees–> late successional trees

Question 16

Name some late successional plant species characteristics

Answer 16

Grow slower, seeds are shade tolerant, grow despite presence of pioneers, cast shadows when grown inhibiting pioneers

Question 17

Monoclimax theory

Answer 17

(Clements 1916): Succession is directional and predictable

Single climax controlled by local environment

Question 18

Polyclimax theory

Answer 18

(Tansley 1939): Many different climax communities can occur depending on:
Soil moisture
Mineral ions
Animal activity
Topography & other factors

Question 19

Climax pattern hypothesis

Answer 19

(Whittaker 1953): Variation on polyclimax idea: a continuum of climax types that vary gradually along environmental gradients