Lecture 4- Succession

Question 1

What is succession a measure of?

Answer 1

Biodiversity changes across temporal scales

Question 2

What process controls successional processes?

Answer 2

DISTURBANCE

Question 3

WHAT ARE THE TWO MODES OF SUCCESSION?

Answer 3

Primary and secondary

Question 4

When does primary succession occur?

Answer 4

From a COMPLETELY sterile beginning, eg. Volcanic eruption

Question 5

When does secondary succession occur?

Answer 5

From a disturbance on ALREADY COLONISED land

Question 6

What are the two succession processes classed as?

Answer 6

Autogenic or allogenic

Question 7

Describe AUTOgenic succession

Answer 7

Species change from BIOTIC interactions

Question 8

Decribe ALLOgenic succession

Answer 8

Species change due to ABIOTIC interactions

Question 9

What type of species are early successional species?

Answer 9

R selected species

Question 10

Describe the characteristics of r selected species that enable them to be successful colonisers (4)

Answer 10

• produce many seeds with high dispersal ability
• no dormancy in germination(quick)
• often n-fixers which allows them to live in regions with low resource avaliability
• allocate more energy to reproduction than biomass (which allows rapid population growth)

Question 11

What type fo species are late successional species

Answer 11

K selected species

Question 12

What are the properties of k selected species that makes them successful in later successional stages?

Answer 12

• large,slow growing (allows monopolisation of light)
• send dormancy, dispersed by animals
• large, containing more resource for growth
• allow more energy to biomass than reproduction

Question 13

Which type of species are more at risk to extinction? Why?

Answer 13

K selected species as they have lesser adaptations to fluctuating environments

Question 14

Describe the r-k continuum

Answer 14

Initially, species have high rates of colonisation and low competitive ability. However,as the community switches from being r to k dominated, the rates of competitively outweigh those fo colonisation

Question 15

How does biomass change throughout succession

Answer 15

Initially a low biomass as early colonisers have low LIFE HISTORY STRATEGIES,but biomass gradually increases with the arrive of large K selected species. However, as competitive exclusion begins (from k selected species), biomass falls from its peak and stabilises

Question 16

Explain how species diversity changes throughout succession

Answer 16

Diversity is initially low as only specialised r selected species can handle unfavourable conditions (eg. Nitrogen fixers), however this rapidly increases until dominant species become prevalent, outcompeting others and stabilising biodiversity at a constant level

Question 17

What are the two mechanism of succession?

Answer 17

Colonisation

Replacement

Question 18

What are the mechanism of succession driven by?

Answer 18

COMPETITIVE EXCLUSION

Question 19

How does colonisation differ between primary and secondary succession

Answer 19

Low in secondary succession as species are already present in the environment. High in primary succession as new species immigrate.

Question 20

What are the two models of species replacement?

Answer 20

1. Inhibition model

2. Facilitation model

Question 21

Outline the inhibition model

Answer 21

Early successional species monopolise resources and completely inhibit the arrival of later species, until something ounces (eg, change in conditions) that allow later species to also access these resources

Question 22

Out line the facilitation model

Answer 22

Each invasive species involved in succession is dependant on site AMELIRATION from earlier colonists. These earlier species make the conditions optimal for the next step in succession (eg. By providing enough nutrients to the soil), and then die as conditions are no longer best suited to them

Question 23

What is a plagioclimax community?

Answer 23

One that is prevented from reaching climax state by human activities