Predictability of dune activity in real dune fields under unidirectional wind regimes

Abstract

We present an analysis of 10 dune fields to test a model-derived hypothesis of dune field activity.The hypothesis suggests that a quantifiable threshold exists for stabilization in unidirectional wind regimes: active dunes have slipface deposition rates that exceed the vegetation deposition tolerance, and stabilizing dunes have the opposite. We quantified aeolian sand flux, slipface geometry, and vegetation deposition tolerance to directly test the hypothesis at four dune fields (Bigstick, White Sands Stable, White Sands Active, and Cape Cod). We indirectly tested the hypothesis at six additional dune fields with limited vegetation data (Hanford, Año Nuevo, Skagen Odde, Salton Sea, Oceano Stable, and Oceano Active, "inverse calculation sites"). We used digital topographic data and estimates of aeolian sand flux to approximate the slipface deposition rates prior to stabilization. Results revealed a distinct, quantifiable, and consistent pattern despite diverse environmental conditions: the modal peak of prestabilization slipface deposition rates was 80% of the vegetation deposition tolerance at stabilized or stabilizing dune fields. Results from inverse calculation sites indicate deposition rates at stabilized sites were near a hypothesized maximum vegetation deposition tolerance (1 m a À1 ), and active sites had slipface deposition rates much higher. Overall, these results confirm the hypothesis and provide evidence of a globally applicable, simple, and previously unidentified predictor for the dynamics of vegetation cover in dune fields under unidirectional wind regimes.

The Imprint of Vegetation on Desert Dune Dynamics

“…We make use of repeat aerial LIDAR topographic data collected in September 2009 and June 2010, to construct digital elevation models (DEMs) with horizontal and vertical resolutions of 1 and 0.1 m, respectively (see section 4). The dunes at White Sands have characteristic lengths of ∼100 m, heights of several meters, and migration rates of several meters per year, so structure and dynamics are well resolved with this data set (Barchyn & Hugenholtz, 2015;Pelletier, 2015;Xia & Dong, 2016). We assume that the rates of dune migration for the 2009-2010 windy season are typical of the migration that would occur in any other given year.…”

“…Vegetation acts to slow dune migration, through three mechanisms: (i) reducing boundary shear stress b due to form drag (Durán & Herrmann, 2006b;Lancaster & Baas, 1998); (ii) binding and consolidation of sand by roots (Waldron, 1977) and (iii) facilitating the formation of sand-stabilizing soil crusts (Figures 1e-1g). In order for plants to gain a foothold, however, their growth rate must outpace the rate of burial by sand on the lee faces of dunes (Barchyn & Hugenholtz, 2015;Durán & Herrmann, 2006b;Jerolmack et al, 2012;Reitz et al, 2010) (Figures 1e-1g). This occurs at a threshold dune migration rate, below which the stabilizing effects of plants result in a positive feedback that further slows dune migration (Baas & Nield, 2007;Durán & Herrmann, 2006b;Pelletier et al, 2009).…”

Vegetation of semi-stable rangeland dunes of the Navajo Nation, Southwestern USA

“…This trait is consistent with Bower's hypothesis of the adaptive advantage of rapid growth in response to sand burial. Vegetation tolerance to sand deposition has been proposed as one component of understanding dune field dynamics (Barchyn and Hugenholtz 2015).…”

Recent greening (1981–2013) in the Mu Us dune field, north‐central China, and its potential causes

“…As a result, restricted aeolian activity would be conducive to vegetation growth and the development of soil crusts, which in turn facilitate dune stabilization. Vegetation could even colonize the lee faces of dunes as a result of an overall reduction in sediment flux across the dune (Barchyn & Hugenholtz, 2015;Z. Xu et al, 2015).…”