title: Secondary dispersal driven by overland flow in drylands: Review and mechanistic model development.
abstract: Seed dispersal alters gene flow, reproduction, migration and ultimately spatial organization of dryland ecosystems. Because many seeds in drylands lack adaptations for long-distance dispersal, seed transport by secondary processes such as tumbling in the wind or mobilization in overland flow plays a dominant role in determining where seeds ultimately germinate. Here, recent developments in modeling runoff generation in spatially complex dryland ecosystems are reviewed with the aim of proposing improvements to mechanistic modeling of seed dispersal processes. The objective is to develop a physically-based yet operational framework for determining seed dispersal due to surface runoff, a process that has gained recent experimental attention. A Buoyant OBject Coupled Eulerian - Lagrangian Closure model (BOB-CELC) is proposed to represent seed movement in shallow surface flows. The BOB-CELC is then employed to investigate the sensitivity of seed transport to landscape and storm properties and to the spatial configuration of vegetation patches interspersed within bare earth. The potential to simplify seed transport outcomes by considering the limiting behavior of multiple runoff events is briefly considered, as is the potential for developing highly mechanistic, spatially explicit models that link seed transport, vegetation structure and water movement across multiple generations of dryland plants.
authors.affiliation: Department of Civil and Environmental Engineering, UC Berkeley, 661 Davis Hall, Berkeley, California 94720 USA.
authors.forename: Sally E
authors.initials: SE
authors.lastname: Thompson
authors.affiliation: Soil, Water and Environmental Sciences, A R O - Volcani Center, Bet Dagan, 50250 Israel.
authors.forename: Shmuel
authors.initials: S
authors.lastname: Assouline
authors.affiliation: Division of Hydrologic Sciences, Desert Research Center, Las Vegas, Nevada 89119 USA.
authors.forename: Li
authors.initials: L
authors.lastname: Chen
authors.affiliation: Nicholas School of the Environment, Duke University, Box 90328, Durham, North Carolina 27708 USA.
authors.forename: Ana
authors.initials: A
authors.lastname: Trahktenbrot
authors.affiliation: Geography and Environmental Development, Ben-Gurion University of the Negev, Be'er Sheva, Israel.
authors.forename: Tal
authors.initials: T
authors.lastname: Svoray
authors.affiliation: Nicholas School of the Environment, Duke University, Box 90328, Durham, North Carolina 27708 USA ; Pratt School of Engineering, Duke University, Durham, North Carolina 27708 USA.
authors.forename: Gabriel G
authors.initials: GG
authors.lastname: Katul
keywords: Eulerian; Lagrangian; Modeling; Overland flow; Seed dispersal; Semi-arid