Growth races in The Mallee: Height growth in woody plants examined with a trait-based model

Plant height and growth are fundamental to the understanding of species ecological strategies, to the description and prediction of ecosystem dynamics and to vegetation management, such as plant species' fire responses. However, a convenient way to characterize the height growth strategies for multiple species have been elusive. We examine the height growth trajectories in 18 woody plant species in a light-saturated, fire-prone, semi-arid environment as well as the influence of functional traits on those trajectories. We test trait-growth relationships by examining the influence of specific leaf area, woody density, seed size and leaf nitrogen content on three aspects of plant growth; maximum relative growth rate, age at maximum growth and asymptotic height. Woody plant species in the semi-arid mallee exhibit fast growth trajectories. Small seeded species were likely to be the fastest to reach maximum height, while large-seeded species with high leaf nitrogen were likely the slowest. Tall species had low stem densities and tended to have low specific leaf area. We modelled plant growth using a hierarchical multi-species model that formally incorporates plant functional traits as species-level predictors of growth, which provides a method for predicting species height growth strategies as a function of their traits. We extend this approach by using the modelled relationships from our trait-growth model to predict: growth trajectories of species with limited data; real species with only trait data and; hypothetical species based only on trait coordination. We hope this highlights the potential to use trait information for ecological inference and to generate predictions that could be used for management.