Asymmetric competition causes multimodal size distributions in spatially structured populations

Area of Science:

• Ecology
• Forestry
• Mathematical modeling

Background:

• Plant populations often show diverse size distributions, even under uniform conditions.
• Understanding the drivers of this size variation is crucial for ecological studies.

Purpose of the Study:

• To investigate the causes of multimodal plant size distributions in even-aged cohorts.
• To model tree growth and competition dynamics in a spatially explicit environment.

Main Methods:

• Developed an individual-based model for tree growth.
• Utilized data from a long-term New Zealand forest study for parameterization.
• Simulated spatially explicit competition and density-dependent mortality.

Main Results:

• Asymmetric resource competition is essential for creating multimodal size distributions.
• Initial spatial clustering effects on size distribution are temporary.
• Restricted resource capture domains lead to complex, multi-layered size distributions.
• The number of size modes correlates with the number of direct competitors.

Conclusions:

• Asymmetric competition within local neighborhoods is the primary driver of complex plant size distributions in even-aged cohorts.
• Spatial dynamics and competition intensity shape population structure.
• The model provides insights into forest stand dynamics and ecological competition theory.