Succession & Distrubance Flashcards
What is ecological succession?
The change in species composition in communities over time, influenced by biotic (living) and abiotic (non-living) factors
Who proposed the Superorganism Hypothesis of succession?
Frederic Clements, who described plant communities as groups of species working toward a stable climax community
How did Henry Gleason’s Individualist Hypothesis differ from Clements’ view on succession?
Gleason argued that individual species respond to fluctuating conditions, and community composition changes generally without deterministic endpoints
What are two main types of succession ?
- primary succession: occurs on bare land (cooled lava, retreating glaciers)
- secondary succession: occurs where life previously existed but the ecosystem was disturbed (abandoned farmland, post-fire areas)
What are pioneer species?
The first organism to colonize an area, characterized by:
- many small seeds
- fast growth rate
- short life cycles
- shade intolerance
Name some characteristics of late-successional species
- fewer, larger seeds
- slower growth rates
- long life cycles
- shade tolerance
What is facilitation in succession?
A process where early species modify the environment, making it more suitable for later species (nitrogen fixation by alder trees)
What is the Intermediate Disturbance Hypothesis?
Species richness leaks at intermediate levels of disturbance, balancing competitive exclusion and colonization opportunities
How do human activities impact ecological disturbances?
- increase disturbance: farming and deforestation promote early-successional species and deplete nutrients
- decrease disturbance: fire suppression leads to late-successional dominance and greater risk of catastrophic events
What are examples of abiotic and biotic disturbances?
- abiotic: hurricanes, fires, volcanic eruptions
- biotic: insect infestations, grazing by animals like bison
What is a climax community?
Traditionally, it’s a final stable stage of succession, but in practice ecosystems are dynamic with multiple stages coexisting due to disturbances
Describe an example of primary succession
The colonization of bare rock by lichens and mosses in Glacier Bay Alaska, following glacial retreat
What role do nitrogen-fixing species play in succession?
They enrich the soil, facilitating the establishment of other plant species
