How do trees respond to species mixing in experimental compared to observational studies?

Area of Science:

• Ecology
• Forestry
• Biodiversity Science

Background:

• Ecologists have long studied tree species diversity's impact on forest productivity across various scales.
• Research has employed diverse methods, including observational studies and experimental designs.

Purpose of the Study:

• To assess the consistency of tree species' growth responses to species mixing across different research approaches.
• To determine if findings from national forest inventories, diversity experiments, and comparative plot networks are transferable.

Main Methods:

• Utilized data from five European national forest inventories (16,773 plots).
• Analyzed data from six tree species diversity experiments (584 plots).
• Incorporated data from six networks of comparative plots (169 plots).

Main Results:

• Confirmed a general positive effect of tree species mixing on species growth, averaging 16%.
• Found no consistency in species-specific growth responses to mixing across the three research approaches.
• This lack of consistency persisted even when comparing plots with similar mixture compositions and forest types.

Conclusions:

• Tree species-specific responses to mixing are not consistent across different research approaches.
• Integrating insights from diverse research methods is crucial for selecting species mixtures that enhance forest biodiversity and functioning.
• Future forest management strategies should account for the variability in species responses observed across different study designs.