Communities - Succession Flashcards
What are the processes and mechanisms of succession?
Succession progresses in seral stages beginning with vegetation and moving into the return of animals
What are the differences between primary and secondary succession?
Primary: starting again from nothing - no existing biota, seed bank, or top layer
Secondary: large setback but not completely starting over - some biota retained, seed bank is present, top layer is present
What are some disturbance processes that may lead to succession?
Fire, deglaciation, earthquakes, flooding…
Link concepts from evolution, physical environment,
populations, etc. to describe succession
The physical environment may be disturbed by chance abiotic events, the species that can adapt will pass on their beneficial traits to their offspring. These individuals will make up the new population of a climax community.
Disturbance
An event that causes damage or destruction to some part of a community or larger landscape
Succession
Process of community-level recovery after disturbance
Resiliance
Ability to recover original condition after a distrubance
Resistance
Ability to avoid displacement from a disturbance
Characteristics of disturbance
Frequency, intensity, scale, return frequency
Disturbance frequency
Regularity of the disturbance event
Disturbance intensity
Severity of the disturbance event
Disturbance scale
Microdisturbance: local-scale (ex. tree falls down)
Large scale stand-replacing: entire community is affected, leads to shifting mosaic succession (patches of varying successional stages)
Return frequency
Regular: cyclical and predictable (ex. seasonal)
Irregular: stochastic and unpredictable
Seral stage
One of several transitional community types (sere) during succession
Climax community
Stable, predictable endpoint to succession, but still dynamic
Characteristics of early succession
Ruderal and survivor species - fast growing, tolerant of high temperatures and light, good dispersers
Characteristics of mid succession
Pioneer trees and shrubs - stress tolerant, shade adapted
Characteristics of late succession
Competitive trees and shrubs - slower growing, less disturbance tolerant, dominant community
Aquatic succession
Stages are called hydroseres - edges of lake fill with sediment, vegetation grows, and eventually the lake is filled in
Alternative stable states
Ecosystems are dynamic and may have several possible stable states. The current state is determined by interactions between species, the species available, and abiotic changes
Facilitation model
Early seral stages help the establishment of later stages by “prepping” the environment
Tolerance model
Species occupy different niches, so they can only exist in certain seral stages where there niches are realized
Inhibition model
Early species inhibit the establishment of later species. Later species only establish themselves as a result of further disturbance
How does vegetation spread (5)?
Vegetative (budding)
Advanced regeneration (young only released when old die)
Long distance dispersal of seed
Serotiny (retention of seed in woody capsules - released by fire)
Seed bank (seed accumulation in the soil)
Succession impacts on life history… early vs. late
Early succession species: short-lived, fast growth, many small seeds
Late succession species: taller, shade canopy, deep roots, longer lived, slow growth, fewer larger seeds
How does disturbance change the structure and function of a community?
Depends on frequency and intensity - often damages soil quality, destroys vertical profile, and decreases biodiversity
Transient climax
Frequent disturbance exceeds resistance & resilience - locked in a particular seral stage
Fire/grazing-maintained climax
Fire/grazing prevents the following seral stages - new climax established
Primary succession
All existing biota are removed, no seed bank, no top layer of soil
Unpredictable climax community, colonized by long-distance dispersal
Ex: deglaciation
Secondary succession
Some biota is retained, seed bank exists, top layer of soil remains
More predictable climax community, shifting mosaic
Ex. clearcut
