Week 6 Flashcards
Define Community?
- The co-occurrence of individuals of several species in time and space
- And the role of interdependences among the species
Assemblages
- The group of species that are present and potentially interacting within a study (or restoration) area
Species Pool
- all species occurring within a biogeographic region
- Much larger scale than local species assemblage
What are assemblage rules?
- broad patterns of species co- occurrence
- ex. species with similar food habits would seldom co-occur
What are the three models of community assemblage?
- Deterministic
- Stochastic
- Alternative stable states
Deterministic community assemblage
- A communities development is seen as the inevitable consequence of abiotic and biotic factors
- Predictable re-assembly after disturbance
Stochastic community assemblage
- Community compostition and structure is essentially random
- Recovery depends on vacant niches and who fills those niches quickly
- Reassembly provides a different community than before
- Any number of new states could develop, depending on
o Organisms present, environmental conditions, historical events
Alternative stable states community assemblage
- Intermediate of deterministic and stochastic – reflects nature most
- Constraints on restructuring recovering communities
- Various trajectories, depending on
o Organisms present, environmental conditions, historical events, element of randomness inherent in all systems
What are the four parameters you need to know to restore a community successfully?
- Components of community assemblages
- The patterns/relationships in community assemblages
- Rules that govern the expression ofthe property (why does the community function the way that it does?)
- The mechanism that caused the pattern
Contrast the ‘community’ approach with the ‘species assemblage’ concept (4).
Species assemblage:
- Smaller scale, could be part of a larger community
- Focuses on identifying the filters and constraints that will modify the species present in a specific area throughout a successional pathway.
- this concept does not discount the need to know if interactions among species are occurring on a larger spatial scale than the restoration site under study,
* but identifies that we only need to know if those interactions serve as constraints to the species on our site of interest.
What are the three species pools to consider?
- Regional species pool: the set of species occurring in a certain biogeographic or climatic region which are potential members of the target assemblage
- Local species pool: the set of species occurring in a subunit of the biogeographic region, such as a valley segment
- Community (assemblages) species pool: the set of species present in a site within the target community
The concept of ecological filters forms one of the main approaches in assembly rules theory; explain the concept of ecological filters and how they influence your approach to the restoration of communities.
- Abiotic and biotic controls/conditions that determine how organisms establish
- Organisms who are adapted, can establish
- Organisms who aren’t adapted will be “filtered” out
- A continual evolution (survival of the fittest)
- The focus is on the end product of numerous interactions between a colonist and the ecosystem components
- Restorationists can use assembly rules at the beginning of restoration projects to determine what factors are limiting/filtering the community
What are some basic abiotic filters to consider in designing your goals for restoring community assemblages (3)?
- climate: rainfall and temperature gradients,
- substrate: fertility, soil water availability, toxicity,
- landscape structure: landscape position, previous land use, patch size, and isolation
Should your restoration of communities be based upon concepts of succession versus assemblage rules? Why?
- Both are intertwined, use both
