Biodiversity & functioning of natural ecosystems I

Question 1

What is diversity

Answer 1

species richness + evenness of spread

Biodiversity (includes diversity w/in species, between species and of ecosystems) can be:
-> Taxonomic (evenness + richness)
-> Phylogenetic (time since divergence)
-> Genetic (alleles, nucleotides, chromosomes etc)
-> Functional diversity (functional groups / traits)

Question 2

The feedback loops

Answer 2

components:

Environment (land use, hunting, pollution, soil type, topography)

Ecosystem funcitoning (decomposition, biomass production, herbivory, pollination) -> permit ecosystem services

Biodiversity

Question 3

origonal paradim:

Answer 3

environment -> biodiversity and ecosystem functioning

ecosystem functioning -> Biodiversity

Environment -> Biodiversity example: latitudinal gradient
- Productivity + diversity have generally +ve relationship (correlation not causation + not for all groups / systems eg. ocean)
- species diversity is higher nearer equator / at lower latitudes (as increased primary productivity and resources)
- Eg. coral reefs + rainforests (exception = penguins)

Environment -> biodiversity: deforestation

Environment -> Productivity -> biodiversity example: Eutrophication and global change
- N is a key limiting resource
- Increased in soild accidently (pollution) and on purpose (fertilisation)
- Environment increases productivity but this reduces diversity

Question 4

Updated paradigm

Answer 4

Biodiversity and environment -> ecosystem functioning

Mechanisms

Lottery effect:
- Not all species are equal so the higher the diversity the greater the chance of the community containing successful species.
- ‘insurance’ against a fluctuating environment

Niche complenetarity:
- Different species in a ecosystem occupy functionally distinct niches and use resources in a complementary way
- Niche differentiation in mixtures can lead to complementarity
- > Resource use
- > pollinators
- > against pests, disease and weeds
- Links to idea to idea of species functional heterogeniety increasing ecosystem functioning
- Eg. wetlands support many species as they occupy different niches (eg. wigeons graze, teal feed in shallows, mallards upend to reach down, shovelers filter surface water, tufted ducks + pochards dive to deeper sediments)

Study showing Complementarity effect -> meta analyses
- Study measured overyeilding of species mixtures relative to expected yields based on monoculture yields of indiv component and their relative abundance in the mixture
- Mixtures on average more productive but not always overyield the best monocultures -> depends in species is redundant or dominant

**Redundant species hypothesis: **
- Caertain species are key and have a large influence on productivity
- Certain species are redundant and have little effect on funcioning as existing species expand their functioning.
- Threshold of biodiversity loss beyond which functioning collapses
- The other way around: Once no. species exceeds this threshold there is no extra benefit of increasing diversity on funcitoning -> saturating effect of biodiversity

**Species functional heterogeniety **
- Different species support different functions, in different places, at different times
- Increasing diversity means greater diversity of functional traits that can
- > increase total resource capture
- > Reduce effect of pests and weeds
- > Increase pollination
- > Increase stability

• Maintaining multiple ecosystem processes requires higher levels of biodiversity than does a single process

Question 5

Testing the effect of biodiversity on productivity:

Answer 5

Biodiversity experiments reveal a general positive relationship between diversity and function

Species knockouts
- artifical plant comunities created in ecotrons -> 16 controlled environment changes
- Biodiversity manipulated (species knocked out) and productivity recorded
- After 40 days, high diversity leads to greater change in abundance

Field Test: Ceder creed
- Gradient of biodiversity and productivity recorded -> number and type of species controlled
- repeated over many years

Question 6

Overview

Answer 6

The interaction between environment, biodiversity and ecosystem functioning

origonal paradigm:
- Environment effects ecosystem funcitoning and biodiversity
- Ecosystem functioning effect biodiversity

new paradigm
- Environment effects ecosystem functioning and biodiversity
- Ecosystem functioning effect biodiversity and vice versa

Why?
- Lottery effect
- redundent species hypothesis
- functional diversity
- Niche complementation