Complementarity among four highly productive grassland species depends on resource availability

Area of Science:

• Ecology
• Plant Ecology
• Biodiversity Research

Background:

• Positive species richness-productivity relationships are frequently observed in biodiversity experiments.
• The influence of resource availability on these relationships in highly productive grass-legume mixtures remains under-explored.

Purpose of the Study:

• To investigate how resource availability (control, fertilization, shading) modifies biodiversity effects in mixtures of highly productive grasses and legumes.
• To test if resource partitioning and facilitation mechanisms are altered by varying resource levels.

Main Methods:

• Established monocultures and mixtures (2-, 3-, and 4-species) of two grasses and two legumes (Jena Experiment).
• Manipulated resource supply through control, fertilization, and shading treatments.
• Quantified community biomass production and analyzed net diversity effects (complementarity and selection effects).

Main Results:

• Community biomass increased with fertilization (+12%) and decreased with shading (-56%) relative to control.
• Net diversity effects were positive under control (+15%) and shading (+72%), but negative under fertilization (-10%).
• Positive complementarity effects were linked to resource partitioning and N2 fixation (control) or carbon-limited partitioning (shading).

Conclusions:

• Resource availability significantly influences the net diversity effects in mixtures of productive grasses and legumes.
• Fertilization reduced positive diversity effects by increasing light competition, while shading enhanced them.
• Complementarity, driven by resource partitioning and facilitation, is a key driver of biodiversity effects, modulated by resource supply.