Linking changes in species–trait relationships and ecosystem function using a network analysis of traits (NAT)

A major challenge in ecology and environmental management is linking changes in community composition to ecosystem functions. We developed the network analysis of traits (NAT) to show changes in community network structure based on the changes in the composition and connectivity between clusters of species that share traits that imply shifts in functional diversity. We tested the application of NAT on a 113 species found on an intertidal sandflat that was subject to experimental nitrogen addition (control [0 g N/m(2) ], medium [150 g N/m(2) ], and high [600 g N/m(2) ]). This allowed us to directly link mechanistic changes in community composition and function with the trait-space network patterns revealed by NAT. We demonstrate that under medium (150 g N/m(2) ) N treatment, functional diversity remained consistent, whereas increasing disturbance to high (600 g N/m(2) ) N treatment affected the species-trait network structure and caused merging of functional clusters implying a loss of functional trait diversity.