Improved modelling of plant competition through traits

Abstract

Competition among individuals, species, and functional groups within natural vegetation stands plays a central role in determining the ecosystem's structure, composition, and productivity by influencing how different plant populations compete for limited resources such as light, water, nutrients, and space. In other words, competition structures the composition of ecological communities by affecting the relative performance of different plant populations; these effects emerge through trait-dependent differences in growth and resource use. Plant traits that influence plant performance, such as growth rates, leaf morphology, and wood density, provide a perspective into the processes and structural factors that govern competition and adaptation to stress. As such, traits can be powerful tools to characterize competitive dynamics and adaptation to stress conditions. Traits are often used in forest ecology and biodiversity research as indicators of plant performance, including species distribution, environmental tolerance, growth, and competitiveness. Similarly, traits reflect functional trade-offs in the evolution of species or in ecological assembly to maximize individual performance under different resource availability or stress conditions. Environmental stress governs community assembly by filtering species distributions and limiting species survival. Understanding and modelling how functional traits and competition influence community structure and productivity under conditions of resource variability is fundamental to community assembly. The variability in available resources for growth, reproduction, and survival creates different growth conditions along environmental gradients, allowing for testing the role of traits, plant strategies, competition, and adaptation to stress conditions in community assembly.

Overall, this research underscores the importance of incorporating functional trait information to model plant competition and ecosystem processes. This study disentangles the community assembly process and productivity by examining how traits, strategies, and environmental conditions interact across gradients. It also shows how such models can simulate ecosystem responses to global environmental changes, offering valuable insights into the dynamic interplay between biotic competition, abiotic stress, and plant strategies in natural ecosystems. Integrating trait-mediated interactions into these models improves predictions of ecosystem dynamics and responses to climate change, deepening our understanding of ecosystem functioning and resilience under future environmental conditions.

Date of Thesis submission	2025
Original language	English
Awarding Institution	Western Sydney University
Sponsors	Australian Government Research Training Program Scholarship
Supervisor	Benjamin Smith (Supervisor), Stefan Olin (Supervisor), Mark Tjoelker (Supervisor), Mikael Pontarp (Supervisor) & Daniel Metcalfe (Supervisor)