communities and ecosystems Flashcards
define ecological community
a community is a group of potentially interacting species that occur together in space and time
how do communities delineate
Communities delineated in different ways
Taxonomic affinity: does not interact with one another
Guild: e.g. all dependant on tree hollows for breeding
Functional groups: roles they play within their community
key processes of ecological communities
The species present in a community can be viewed as the outcome of a set of filters
E.g. a regional species pool can have dispersal limits - the outcome of evolution and biogeography
Abiotic filter - the fundamental niches of the species control the abiotic filter through environmental limits
Biotic filter - the realised niches of the species control the biotic filter through species interactions
what are ecological communities influenced by?
Regional species pool
Dispersal
Environment
Species interactions
ecological communities are constantly changing
Communities are never static
Changes due to changes in
- regional species pool
- dispersal
- environment
- species interactions
Can also all be contributed to chance
Evolution and extinction
Dispersal success and failure
Occurrence of disturbance
changes in the species pool
- Evolution and diversification
- Extinction
changes in dispersal
- Species introduced by people are a clear example of changing dispersal
- But dispersal occurs naturally too (often haphazardly)
Environments disturbances:
- Discrete events that change resource availability and/or the physical environment
- Natural: bushfires, floods, cyclones, volcanoes, disease
- Human-generated: habitat clearing, pollution
Species interactions
Invasive species can have large impacts through their species interactions
Succession in vegetation communities
- Succession: natural changes in the composition and structure of an ecological community over time
- The replacement of one community by another
Defining vegetation communities by structure
- Tree height
- Crown - the tallest layer of foliage
- Crown cover - the proportion of ground covered by the crown (0-100%)
Communities can differ based on
- Their species (and the relative abundance of the species)
- The sizes and layers of vegetation (for plant communities)
define species diversity
the composition of a local ecological community with respect to its richness (number of species), evenness (distribution of abundances of the species), or both
Species diversity → stability and productivity
↑ species diversity
↑ trait diversity
↑ functional diversity
↑ redundancy and opportunity
Functional diversity
Greater diversity
Resource consumption, transformation and provision
Physical environment
Chemical environment
Interactions among species
Thus often see links between species diversity and functional diversity
Primary succession
-Occurs when organisms colonized bare rocks introduced by retreating glaciers or volcanic eruptions
- Rock lacks both soil and life forms
Pioneer species
hardy organisms that can thrive in harsh conditions
E.g. lichen: symbiotic organisms comprised of a fungus and algae or cyanobacteria
Climax community
a community with a relatively stable species composition
Secondary succession
- Occurs when organisms recolonise a habitat that was cleared by a disturbance
- The climax community regrown is very different from the first climax community
Communities can differ based on
- Their species (and the relative abundance of the species)
- The sizes and layers of vegetation (for plant communities)
Defining vegetation communities by structure
- Tree height
- Crown - the tallest layer of foliage
- Crown cover - the proportion of ground covered by the crown (0-100%)
Species diversity
the composition of a local ecological community with respect to its richness (number of species), evenness (distribution of abundances of the species), or both
Species diversity → stability and productivity
↑ species diversity
↑ trait diversity
↑ functional diversity
↑ redundancy and opportunity
Functional diversity
Greater diversity
- Resource consumption, transformation and provision
- Physical environment
- Chemical environment
- Interactions among species
Thus often see links between species diversity and functional diversity
Communities and functional diversity
Species diversity doesn’t influence community dynamics directly, but species diversity can increase functional diversity