Edited by Andrea Rinaldo, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland, and approved June 26, 2018 (received for review December 14, 2017)
Since the appearance of land plants in Devonian time, vegetation has played a key role in the coevolution of life and landscapes as a result of mutual orchestrated processes between vegetation characteristics, environmental disturbances, and soil allometry. We mathematically frame the interactions between these three processes into a single parameter that discriminates between vegetated and bare states. In agreement with theories linking ecosystem development to hydrosphere and lithosphere connectivity, this theory suggests that the vegetation biodiversity of river sediment deposits occurs as a selection process in and among the biomechanical characteristics of species. Verified against field observations, this theory allows for water management applications and has important implications to understand natural and man-induced changes in biogeomorphological styles.
Conditions for vegetation spreading and pattern formation are mathematically framed through an analysis encompassing three fundamental processes: flow stochasticity, vegetation dynamics, and sediment transport. Flow unsteadiness is included through Poisson stochastic processes whereby vegetation dynamics appears as a secondary instability, which is addressed by Floquet theory. Results show that the model captures the physical conditions heralding the transition between bare and vegetated fluvial states where the nonlinear formation and growth of finite alternate bars are accounted for by Center Manifold Projection. This paves the way to understand changes in biogeomorphological styles induced by man in the Anthropocene and of natural origin since the Paleozoic (Devonian plant hypothesis).
Author contributions: M.B.B., P.P., and C.C. designed research, performed research, and wrote the paper.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1721765115/-/DCSupplemental.
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