Wind Characteristics of Mesquite Streets in the Northern Chihuahuan Desert, New Mexico, USA

Abstract

Past research has shown that the most important areas for active sand movement in the northern part of the Chihuahuan Desert are mesquite-dominated desert ecosystems possessing sandy soil texture. The most active sand movement in the mesquite-dominated ecosystems has been shown to take place on elongated bare soil patches referred to as "streets". Aerodynamic properties of mesquite streets eroded by wind should be included in explaining how mesquite streets are more emissive sand sources than surrounding desert land. To understand the effects of wind properties, we measured them at two flat mesquite sites having highly similar soil textures but very different configurations of mesquite. The differences in wind properties at the two sites were caused by differences of size, orientation, and porosity of the mesquite, along with the presence of mesquite coppice dunes (sand dunes stabilized by mesquites growing in the dune and on its surface) found only at one of the two sites. Wind direction, u * (friction velocity), z 0 (aerodynamic roughness height) and D (zero plane displacement height) were estimated for 15-m tower and 3-m mast data. These aerodynamic data allowed us to distinguish five categories with differing potentials for sediment transport. Sediment transport for the five categories varied from unrestricted, free transport to virtually no transport caused by vegetation protection from wind forces. In addition, "steering" of winds below the level of the tops of mesquite bushes and coppice dunes allowed longer parallel wind durations and increased wind erosion for streets that aligned roughly SW-NE.

Vegetation in Drylands: Effects on Wind Flow and Aeolian Sediment Transport

“…By moving away from homogenous mean values to describe the roughness density and drag partition, Okin's [58] approach resolves the heterogeneous wind shear velocity between roughness elements and over the soil surface. This notion is supported by field observations that flux is not ubiquitous across an entire landscape during a transport event [51]. Okin's [58] method implies that surface roughness moderates the wind erosivity, rather than the threshold shear velocity for soil entrainment.…”

“…During the 1990s, more attention was given to the development of drag partitioning techniques that could establish the wind momentum flux at the soil surface in the presence of roughness elements. The schemes of Raupach [57,121] and Marticorena and Bergametti [118] were widely adopted on the basis of their good agreement with wind tunnel experiments using solid objects on non-complex surfaces (e.g., [51,71,[140][141][142][143]). However, the drag partition schemes have also been found to be limited in application in several respects.…”

“…The schemes seek to establish the mean (or maximum) shear stress ratio in the absence of information about the heterogeneity of roughness on the land surface [87]. The spatial distribution of vegetation has been shown to affect horizontal sediment flux, even at low roughness densities [28,51,119,[144][145][146]. The roughness distribution effects on aeolian sediment transport are also nuanced, in that the sediment mass flux may not always be significantly affected as long as vegetation is not overly clumped together [147].…”

“…This results in stress being transferred to the inter-canopy surface, and potentially greater sediment transport [52,75]. In the case of skimming flow (>~40% cover [43]), the increased drag from the vegetation acts to displace z 0 upwards (establishing a zero-plane displacement height, d), which simultaneously extracts momentum from the surface wind and increases wind shear stress above the canopy (e.g., [47][48][49][50][51][52]76,77]). The absorption of additional stresses by the plants therefore decreases the erosion potential at the surface, despite the additional above-canopy shear stress induced by the increased surface roughness.…”

Spatial variability of soil and nutrient characteristics of semi‐arid grasslands and shrublands, Jornada Basin, New Mexico

“…Tarbush vegetation is found within the lower piedmont slope and the alluvial plain. Mesquite shrubs occur on soil such as the Pintura series (great group: torripsamments), which is characterized by nebkha dunes, with barren blown-out areas between the dunes (Gillette and Pitchford, 2004;Gillette et al, 2006). This association exists predominantly in the eastern and central part of the Jornada Basin.…”