Leaf and root traits are partially coordinated but they show contrasting multi-trait-based community trait dispersion patterns in a subtropical forest

The ecology of plant species relies on the synchronous functioning of leaves and roots, but few studies have simultaneously examined the community trait dispersion patterns (CTD) of both organs. We measured 16 analogous leaf and root traits on 44 co-occurring woody species in a subtropical forest in southern China, examining whether leaf and root traits were coordinated, organized into parallel trait axes, exhibited similar CTD, and displayed consistent responses in CTD and community-weighted means of (CWM) traits over environmental gradients. While the first axes of leaf and root trait variation similarly exhibited a fast – slow continuum, leaf traits covered a secondary ‘carbon economics’ axis, contrasting to root traits depicting a collaboration axis reflecting species’ mycorrhizal dependency. Analogous leaf and root chemical traits were generally coordinated but less so for morphological traits. At the community level, changes in the CWM of the first axes were generally consistent among organs with more conservative traits found as increasing elevation but not for the second axis. While root traits became thinner and more conservative as soil phosphorus decreased, leaf traits rarely varied. When different trait axes were combined, leaf traits were overdispersed but tended to converge with increased elevation and soil potassium and phosphorus levels, whereas root traits were clustered but tended to diverge along the same gradients. Our study highlights fine filtering of different suites of traits above- and below-ground, which in turn might reduce overall niche overlap among species and promote coexistence with diverse functional designs.