Lecture 13: Linking Biodiversity to Ecosystem Functioning

Gonzalez

How much biodiversity do grasslands need?

• 200 plant species

How much biodiversity do North American lakes need?

• 80 algae species

How much biodiversity do deciduous forests need?

• 53 tree species

How much biodiversity to tropical forests need?

• 2000+ plants

How much biodiversity do North American streams need?

• 120 algae

How much biodiversity does the open ocean need?

500 phytoplankton

Biodiversity-Ecosystem Functioning (BEF)

• Old paradigm: Environmental variation drives biodiversity and ecosystem functioning

• New paradigm: Biodiversity and environmental variation jointly drive biodiversity and ecosystem functioning

Ecosystem functioning

Stocks of biomass, flow of nutrients, or fluxes of gases

Ecosystem multifunctionality

When biodiversity promotes the supply, persistence, and stability of multiple ecosystem functions above a certain level

Ecosystem services/ nature’s contributions to people

Subset of functions of relational value to humans

Ecosystem

Combined plant and animal communities and physical environment

“Complementarity” model of ecosystem diversity and function

• Species functionally complement each other because each niche has a function

“Rivet” model of ecosystem diversity and function

• After a certain amount of species, there is redundancy

“Drivers and passengers” model of ecosystem diversity and function

• Some species are drivers and contribute strongly to ecosystem function

• Some species are passengers and contribute only to species richness

Functional traits

• Influence ecosystem properties (effect traits)

• Influence species response to environmental conditions (response traits)

These can be used to group species

Functional diversity, plotted

Area corresponds to functional diversity

2 mechanisms by which adding a species can promote function

• Complementarity: Increased function due to resource partitioning or facilitation

• Selection: Greater likelihood of diverse communities being dominated by a competetively superior, high-performing species

Selection effect

• When species with higher-than-average yields when grown alone dominate the functioning of a multispecies community

Complimentarity

• Species yields are higher on average that expected based on average monoculture yield