Unravelling the clonal trait space: Beyond above-ground and fine-root traits

Plant trait variation is constrained by mechanical and energetic trade-offs as attested by the global spectrum of plant form and function and the fine-root economics space for above- and below-ground traits. However, traits that are key for fitness maintenance in some plant groups, such as clonal and bud bank traits, have not yet been integrated within the frameworks provided by the above-ground and the fine-root economics space. By using an extensive dataset encompassing above-ground, fine-root, clonal and bud bank traits of 2000 species of Central European herbs, we asked whether clonal and bud bank traits correspond to the placement of species in the above-ground or fine-root trait space. Perennial clonal and non-clonal herbs show indistinct positioning within the above-ground and fine-root trait spaces. This extends and reinforces previous fragmentary evidence of weak correlations between clonal and bud bank traits and above-ground trait dimensions. Additionally, we identify for the first time a limited correlation between clonal and fine-root traits as well. This disconnection suggests that clonal traits operate independently from other trait spectra. For this reason, we introduce the concept of a ‘clonal trait space’ for clonal herbs. The first dimension of this space is defined by bud bank size and the persistence of clonal connection, reflecting a gradient of species specialisation for on-spot persistence and tolerance to disturbance (persistence dimension). The second dimension, defined by multiplication rate and lateral spread, reflects a specialization axis for clonal multiplication and horizontal size dimension (clonal multiplication dimension). Clonal trait dimensions add non-redundant information to the above-ground or fine-roots trait space.