3 Biodiversity and Ecosystem Functioning (BEF) Flashcards
What is BEF?
Biodiversity and Ecosystem Functioning
- unterstand, how changes in species composition alter ecosystem functions
- what are the consequences led by loss or gain from species?
Key Questions of BEF
- Are aspects of ecosystem functioning dependent on biodiversity?
- How sensitive are ecosystem processes to changes in biodiversity?
- How do individual species affect ecosystem processes?
- biodiversity used to be seen as epiphenomenon driven by abiotic environment and ecosystem functioning
- more recently research look at reverse effect: effect of biodiversity on ecosystem functioning and abiotic environment (major changing science!)
Tilmann Experiment (1999)
- Hypothesis: increase in biodiversity leads to an increase in productivity, an increase in stability at the community level and a reduction in susceptibility to invasion by alien species
- experimental work (not mentioned how)
-experimental evidence: biodiversity does indeed affect ecosystem processes - evidence from field experimental studies
-results: species diversity increases plant biomass production in grassland
sampling effect (Tilmann)
- mean biomass production increases with plant species richness
because
- species-rich ecosystems have a higher probability of containing highly productive species
- high productivity can be achieved for particular combinations of species even at low sp richness
complementarity (Hector)
- when increasing diversity results in increasing numbers of species that are complementary rather than competitive in their use of resources
- they are exploiting different niches, such as rooting depths, and allowing more effective use of available resources
- if niches are complementary, adding species could increase process rates linearly
- as niches overlap the response should saturate
biodiversity experiments
- biodiversity experiments using synthetic communities due to sampling
- do communities, with a higher phenotypic diversity have a greater probability of containing a higher phenotypic trait diversity? and higher productivity? due to their different functional groups and particular traits?
high species richness –> higher trait diversity –> higher productivity ?
Hypothetische Mechanismen bei Experimenten zur biologischen Vielfalt unter Verwendung synthetischer Gemeinschaften. Bei der Bildung von Gemeinschaften spielen Stichprobeneffekte eine Rolle, d. h. Gemeinschaften mit mehr Arten haben eine größere Wahrscheinlichkeit, dass sie eine höhere phänotypische Merkmalsvielfalt aufweisen. Die phänotypische Vielfalt wird dann durch zwei Hauptmechanismen auf Ökosystemprozesse übertragen: Dominanz von Arten mit bestimmten Merkmalen und Komplementarität zwischen Arten mit unterschiedlichen Merkmalen. Zwischenszenarien beinhalten Komplementarität zwischen bestimmten Arten oder funktionalen Gruppen oder, äquivalent dazu, die Dominanz bestimmter Untergruppen von komplementären Arten.
functional diversity of an ecosystem.
What is it and what is it governed by?
- range of functions performed by organisms of a system
- assumed that the functioning of an ecosystem is governed by
1) functional traits of individuals
2) their distribution and abundance
3) their biological activity
functional traits
(SRF / SEF)
- specific trait associated with biogeochemical processes or ecosystem properties
- functional traits of species and their effects on ecosystems and tolerance of environmental changes
- SEF as a species’ capacity to affect an ecosystem property
- SRP as the ability of a species to maintain or enhance its population as the environment changes
- Specific Effect Functions (SEFs)
- Specific Response Function (SRFs)
examples:
-Nitrifying and denitrifying bacteria
Turf and canopy vegetation
Decomposer and predators
functional types/ groups
- individuals or species that possess a common set of functional traits
- taxa-unrelated
- traits important in determining a given ecosystem function that may be shared among multiple species in an assemblage
–> dividing species with similar eco functions into functional groups
e.g. filter feeders
developing functional classification schemes difficult - why?
1)
- traits may only be expressed by one or a few species in an assemblage
-some species may habe bundles of traits that are unique
-due to bundle they can’t be classified in priori functional groups
2)
- expression of functional traits only in a context or a certain life stage (e.g. only in larva stage), time or condition
Redundancy
- grouping species into functional groups makes inference on a degree of functional redundancy or equivalency of traits among species (e.g. nitrogen fixers –> same trait, different taxa and species)
- if most species exhibit unique important traits –> strong relationship between taxonomic (TD) and functional (FD) diversity (e.g. function: ecosystem engineering)
- if many species exhibit similar traits (=redundant traits) –> TD and FD-relationship weak
- if key functional traits are distributed in a uniform fashion among species, attempts to classify species into distinct functional groups may inhibit attempts to determine the TD–FD relationship
- level of redundancy is identified by relationship between FD and TD:
more species –> more traits –> the more linear the relationship
relationship between TD and FD
-three possible relationships:
1) top: when rare species are functionally redundant
2) middle: when every species contributes to functioning and is equally abundant
3) down: when species carry unique functional traits (key stone)
hypothetical relationships between biodiversity and ecosystem processes
Consequences of losing species
- extinctions are not random –> related to their traits
- size matters: large species loss has effect on ecosystem (top down)
- we need to maintain species at a minimum because the changing environment is stressful for many species
- we don’t just want the minimum number of species
- Redundancy (more species with same function) is our safety
- we have to determine significant species
