Modelling vegetated dune landscapes

Abstract

[1] This letter presents a self-organising cellular automaton model capable of simulating the evolution of vegetated dunes with multiple types of plant response in the environment. It can successfully replicate hairpin, or long-walled, parabolic dunes with trailing ridges as well as nebkha dunes with distinctive deposition tails. Quantification of simulated landscapes with eco-geomorphic state variables and subsequent cluster analysis and PCA yields a phase diagram of different types of coastal dunes developing from blow-outs as a function of vegetation vitality. This diagram indicates the potential sensitivity of dormant dune fields to reactivation under declining vegetation vitality, e.g. due to climatic changes. Nebkha simulations with different grid resolutions demonstrate that the interaction between the (abiotic) geomorphic processes and the biological vegetation component (life) introduces a characteristic length scale on the resultant landforms that breaks the typical self-similar scaling of (un-vegetated) bare-sand dunes. Citation: Baas, A. C. W., and J. M. Nield (2007), Modelling vegetated dune landscapes, Geophys. Res. Lett., 34, L06405,

Remote sensing and spatial analysis of aeolian sand dunes: A review and outlook

“…In addition to detecting different successional stages across a vegetated or semi-vegetated dune field, the ability to resolve spatial patterns of vegetation types is important for linking empirical observations with numerical models, and for understanding the degree of forcing that would be required to reactivate stabilized or stabilizing dunes. In the numerical model of Baas and Nield (2007) it was found that the addition of two types of vegetation (shrubs and grasses) was necessary to form realistic parabolic and nebkha dunes. In this regard, multispectral imagery could and should be used to test this parameterization, and if needed, guide the refinement of the numerical growth characteristics.…”

Fine-scale patterns of vegetation assembly in the monitoring of changes in coastal sand-dune landscapes

“…In transgressive profiles, Ammophila arundinacea becomes an absolute dominant, not only because of its capability to survive deep sand burial (García-Mora et al 1999, Levin et al 2008), but also due to the reduction or disappearance of other species (as indicated by its negative correlation to other biological metrics; cf. Table 3), possibly due to loss of facilitation efficiency under extreme stress conditions (Brooker et al 2008).…”

“…7), even though only a residual percentage (3%) of the compositional variation in the vegetation dataset was found to be due to interactions between biogeography and local dynamics. Nonetheless, even along our narrow biogeographic gradient (ca 200 km long), a decrease in facilitation efficiency under extreme stress conditions (Brooker et al 2008) may be involved in the loss of unspecialized plants ('type I' species of García-Mora et al 1999) related to both biogeography (i.e. water stress gradient due to southwards decreasing rainfall; Forey et al 2008) and local dynamics (i.e.…”

“…Nonetheless, a close relation between vegetation and sediment transport/deposition in coastal dunes has been reported by a number of authors (Maun and Perumal 1999, Baas 2007, Meerkerk et al 2007, Levin et al 2008. This relationship can provide deeper insights into the dynamics of dune landscapes, which can then support a range of applications in management, monitoring and restoration (Levin et al 2006, Baas andNield 2007).…”

“…These gradients determine the organization of vegetation profiles along a succession of characteristic geomorphologic features from the beach inwards (Feagin et al 2005b, Lomba et al 2006, 2008, Greaver and Sternberg 2007, Lortie and Cushman 2007. For this reason, the quantification of vegetationgeomorphology interactions is considered crucial in the assessment of impacts of environmental changes, including the establishment of reliable indicators (Baas and Nield 2007, Levin et al 2008, Lomba et al 2008. Even though worldwide vegetation zonation in foredunes has been demonstrated decades ago (Doing 1985) and extensively confirmed in recent years (Wilson and Sykes 1999, Dech and Maun 2005, Isermann 2005, Levin et al 2008, Lomba et al 2008, the actual factors driving that zonation are yet controversial due to covariance and interaction among environmental factors (Dech andMaun 2005, Forey et al 2008).…”