A trait‐based approach to community assembly: partitioning of species trait values into within‐ and among‐community components

TLDR

Plant functional traits vary along environmental gradients and among species in similar conditions, complicating synthesis of functional and community ecology. The study introduces a trait‑based approach that decomposes species’ trait values into alpha and beta components. The approach defines beta values as a species’ position along a community‑level trait gradient and alpha values as the deviation from the community mean of co‑occurring taxa. In coastal California woody plant communities, beta trait values for specific leaf area, leaf size, wood density, and maximum height covary strongly with soil‑moisture gradients, while alpha values show little correlation, indicating independent axes of differentiation and providing a novel framework to integrate functional ecology with community assembly theory.

Abstract

Plant functional traits vary both along environmental gradients and among species occupying similar conditions, creating a challenge for the synthesis of functional and community ecology. We present a trait-based approach that provides an additive decomposition of species' trait values into alpha and beta components: beta values refer to a species' position along a gradient defined by community-level mean trait values; alpha values are the difference between a species' trait values and the mean of co-occurring taxa. In woody plant communities of coastal California, beta trait values for specific leaf area, leaf size, wood density and maximum height all covary strongly, reflecting species distributions across a gradient of soil moisture availability. Alpha values, on the other hand, are generally not significantly correlated, suggesting several independent axes of differentiation within communities. This trait-based framework provides a novel approach to integrate functional ecology and gradient analysis with community ecology and coexistence theory.