diversity changes Flashcards
diversity changes?
opulation declines and extinction of species
6th major extinction
how do invasions lead to diversity changes
- Accelerated by humans - transport and travel
○ Deliberate or not
○ Homogenizes ecosystems
functional types? ex?
- Groups of sp that are ecological similar with respect to their effects on ecosystems or their response to environmental change
○ Ex. N fixing plants - symbiotic relationships with bacteria- Important bc fundamentally, diversity is a really hard issue to deal with
Ecosystem processes vs effect of species number
- Npp as a function of species richness
- Curved line -where functional groups come into play
- Effect of adding new species depends on whether they are functionally redundant
- Tends to be low functional redundancy when species richness is low (more ecosystem roles or functions to fill)
- Species rich communities have higher functional redundancy (may lead to stability)
- Ie. Threshold where each species starts to serve a particular function that is not buffered by functional group redundancies
dominant vs keystone sp?
- Dominant species - species that are most abundant (or have largest biomass) in a community
- Keystone species- species that, relative to its biomass or abundance, has a disproportionately large impact on community structure
Minimal impact of rare species in terms of response
- Keystone species- species that, relative to its biomass or abundance, has a disproportionately large impact on community structure
keystone vs compensating?
- Keystone vs compensating
- The composition of diversity can alter ecosystem processes in different ways
invasion ex
- Plant invasive to hawaii
- How nitrogen fixing plant impacted basic ecosystem functions
- In each graph, where the invasive plant is present,
- Changing soil dynamics in N
- Mineralization rate - where there are invasions
- Hawaii is very vulnerable to invasions as most islands are
invasions california ex
- Natural community are bunch grasses
- Arid system - Mediterranean type
- Opportunity to invade systems due to their functional systems
- European grass + eucalyptus from australia - invasive in cali
- Tapping into ground water better by size
- Eucalyptus oil produced is an issue
- Species effect on microclimate
- Ecosystems
heat fluxes from decidous and boreal forest
- look in text
ecological services?
- Ecological services - processes and resources of value to humans provided by ecological systems. These processes and resources are typically called ecological functions
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ecosystem function
- Ecosystem function - process within an ecosystem such as biomass production, nutrient cycling, or carbon sequestration. If function is diminished, so too is the quality of the service
diversity-function relationships
* Ex. Cedar creek
- Experiments in minnesota, fundamental to understanding diversity
- This was the first time the idea of diversity was emperically tested
- Replication of different levels of diversity + combos of species
- Could measure what is taking place in the plots
- Looked at how diversity changed relatively
- Saturating curve - yield increases over time with more diverse plots being more productive over the 15 yr study
- Why increase in productivity with diversity?
○ Three main mechnisms proposed:
§ Complementarity: based on niche theory; highest in ecosystem being most fully exploited
§ Facilitation: some species enhance growth of others
§ Sampling effect: based on the assumption that functions of communities with low species evenness are driven by dominant species
□ Ie. The more species you have, the higher chance the species you pick has higher productivity than if you pick just one species
why did nitrate decrease in cedar creek
○ Nitrate decreases bc its being used at a higher rate - nutrient partitioning
