Do plant communities show constant final yield?

Area of Science:

• Plant Ecology
• Community Ecology
• Ecosystem Dynamics

Background:

• Constant final yield (CFY) describes how plant monoculture biomass production plateaus at higher densities.
• Understanding if CFY applies to plant communities is crucial for predicting community-level dynamics.
• This phenomenon is considered a fundamental principle in plant ecology.

Purpose of the Study:

• To experimentally test if plant mixtures exhibit constant final yield (CFY).
• To determine if species' proportional biomass contribution remains stable in mixtures above CFY density.
• To investigate the role of density dependence in plant community structure.

Main Methods:

• Conducted glasshouse experiments over three years using "community density series" with varied overall densities but constant species proportions.
• Grew mixtures of annual and perennial herbaceous species, alongside monocultures, in mesocosms and pots.
• Harvested, separated, dried, and weighed aboveground biomass for each species.

Main Results:

• Plant mixtures demonstrated classical constant final yield (CFY) behavior.
• Species' proportional biomass contributions in mixtures showed minimal change above the density at which CFY was reached.
• Evidence for CFY was stronger in species mixtures than in monocultures.

Conclusions:

• Constant final yield (CFY) is applicable to plant communities, particularly those composed of annual species.
• Individual species' competitive performance stabilizes once CFY is reached in mixtures.
• Plant coexistence theory should incorporate both density and frequency dependence for densities below CFY.