Decadal changes in fire frequencies shift tree communities and functional traits

Area of Science:

• Ecology
• Global Change Biology
• Forestry

Background:

• Global change is causing persistent shifts in fire regimes worldwide.
• Understanding tree community sensitivity to altered fire frequencies is crucial for predicting ecosystem changes.
• The factors influencing this sensitivity remain poorly understood across diverse ecosystems.

Purpose of the Study:

• To investigate the overall effects of fire on tree communities.
• To identify factors controlling tree community sensitivity to multi-decadal fire regime alterations.
• To examine these effects across savanna and forest ecosystems in tropical and temperate regions.

Main Methods:

• Studied 29 sites with documented multi-decadal changes in fire frequency.
• Compared tree stem density and basal area in burned versus unburned plots over 50 years.
• Analyzed functional traits of trees in relation to soil nutrients and fire frequency.

Main Results:

• An average fire frequency (one fire every three years) reduced tree stem density by 48% and basal area by 53% over 50 years.
• The most significant changes were observed in savanna ecosystems and areas with pronounced wet or dry seasons.
• Frequent burning favored trees with low nitrogen and phosphorus content and efficient nitrogen acquisition via ectomycorrhizal symbioses, indicating fire-driven nutrient impacts.

Conclusions:

• Tree community responses to altered fire regimes are complex, influenced by climate, vegetation, and fire behavior.
• The coupling between fire-induced nutrient loss and plant functional traits is a key determinant of tree sensitivity.
• Predicting future ecosystem structure requires integrating fire characteristics, climate, and plant trait responses.