Strategy Space and the Disturbance Spectrum: A Life-History Model for Tree Species Coexistence

Area of Science:

• Ecology
• Forest Science
• Evolutionary Biology

Background:

• Forest ecosystems are shaped by disturbance regimes (type, size, intensity, frequency).
• Tree life-history traits are hypothesized to be adaptations to these specific disturbance regimes.
• Understanding species coexistence requires integrating disturbance dynamics with plant traits.

Purpose of the Study:

• To propose a framework defining tree strategy space based on key life-history traits.
• To develop a fitness model elucidating trait interactions under varying disturbance regimes.
• To test the model's predictive power for species composition and richness.

Main Methods:

• Defined four axes of tree strategy space: shade tolerance, tree height, vegetative reproduction, and seed dispersal.
• Developed a fitness model to simulate trait evolution and species coexistence.
• Validated the model using data from eastern US, boreal Canada, and SW US woodlands.

Main Results:

• The fitness model demonstrates how fluctuating disturbance regimes promote species coexistence.
• The model accurately predicts the number of common tree species in diverse North American forest types.
• Explanations for latitudinal gradients in tree species richness are provided.

Conclusions:

• A strong relationship exists between disturbance characteristics and forest species composition.
• The model successfully predicts species coexistence by integrating life-history traits and disturbance regimes.
• This approach offers a unified explanation for forest diversity patterns across different scales.