Geographic scale and disturbance influence intraspecific trait variability in leaves and roots of North American understory plants

1. Considering intraspecific trait variability (ITV) in ecological studies has improved our understanding of species persistence and coexistence. These advances are based on the growing number of leaf ITV studies over local gradients, but logistical constraints have prevented a solid examination of ITV in root traits or at scales reflecting species’ geographic ranges. 2. We compared the magnitude of ITV in above- and below-ground plant organs across three spatial scales (biophysical region, locality, plot). We focused on six understory species (four herbs, two shrubs) that occur both in disturbed and undisturbed habitats across boreal and temperate Canadian forests. We aimed to document ITV structure over wide ecological and geographical scales by asking: 1) What is the breadth of ITV across species range-scale?; 2) What proportion of ITV is captured at different spatial scales, particularly when local scale disturbances are considered? and 3) Is the variance structure consistent betwee...