Variation cascades: resource pulses and top-down effects across time scales

Area of Science:

• Ecology
• Community Dynamics
• Theoretical Ecology

Background:

• Traditional ecological theories focus on equilibrium dynamics.
• Limited understanding of community responses in fluctuating environments.

Purpose of the Study:

• Extend top-down and bottom-up theories to fluctuating environments.
• Analyze how primary productivity fluctuations affect food web variability.
• Provide a unified method to assess perturbation time scales on community responses.

Main Methods:

• Derived population frequency response in trophic communities.
• Transformed time-based data to the frequency domain.
• Analyzed variability patterns across different trophic levels.

Main Results:

• Low frequencies: primary producers and secondary consumers show high variability; primary consumers are stable.
• Top-down effects create alternating variability patterns (variation cascades).
• Intermediate frequencies amplify variation; high frequencies attenuate it.

Conclusions:

• Novel theory for community responses to productivity fluctuations.
• Indirect species interactions are key drivers across the frequency spectrum.
• Frequency domain analysis unifies understanding of ecological dynamics.