Particle production and aeolian transport from a “supply‐limited” source area in the Chihuahuan desert, New Mexico, United States

Abstract

Abstract. Wind erosion mechanisms were investigated for the "scrape site" at the Jornada Experimental Range near Las Cruces, New Mexico, in the Chihuahuan desert. The scrape site was denuded of vegetation and scraped flat in 1991. We adopted the site in 1994 because it offered an opportunity to study wind erosion mechanisms for a large area of unprotected sandy and crusted soil in an otherwise natural setting and over a period of several years. We installed and operated the following instrumentation for a period of 35 months' three meteorological towers, each 2 m in height, with wind speed sensors at 0.2, 0.5, 1.0, and 2.0 m above ground; air temperature at 0.2 and 2 m height; rain gauge; seven sets of particle collectors at 0.1, 0.5, and 1.0 m heights; and three fastresponse particle mass flux sensors at 0.02, 0.1, 0.2, and 0.5 m heights; all along a transect crossing the site and parallel to the predominant southwesterly wind direction. The minimum threshold friction velocity for the scrape site with a thin layer of loose material was 25 cm s -•. This minimum threshold velocity increased to as high as 100 cm s -1 depending on the degree of particle depletion and the site's status which varied between supply unlimited just after a high wind episode and supply limited which was more typical for the rest of the time. The dominant mechanism producing fresh sediment for transport was sandblasting of the surface crust. The measurements showed that supply and availability of loose, fine particles on the surface is a strong control of rates of erosion rather than wind energy alone. IntroductionIn 1991 a unique study area for long-term wind erosion was created at the U.S. Department of Agriculture Jornada Experimental Range, a working ranch in a broad, sandy, and dry river valley northeast of Las Cruces, New Mexico. A large variety of vegetation types are present, including creosote bush, black gramma grass, and mesquite dune areas. This site was termed the "scrape site" because it was denuded of vegetation and scraped flat for a series of wind erosion experiments. In 1994 we adopted the site as part of a much larger LongTerm Ecological Research (LTER) project to quantify nutrient transport into and out of a desert ecosystem. The site was valuable in two ways: (1) being devoid of vegetation, it offered the opportunity to study wind erosion mechanisms for a large area of unprotected soil in an otherwise natural setting; and (2) because of the time span of LTER studies, these mechanisms could be studied over a period of several years. When we first visited the site in 1994, we had the following information: We hypothesized that the area was acting as a supply-limited source and designed a sampling program to investigate and answer our questions.

Modelling Wind Erosion and Dust Emission on Vegetated Surfaces

“…With their biomass largely below the saltation layer, grasses are abraded and buried by sand particles, whereas shrubs are largely spared this fate. Growth of new plants (including annuals) that rely on nutrients (Gillette and Chen, 2001) and plant-available N and P have been reduced by 89% and 78%, respectively (Okin et al, 2001b). No vegetation has regrown on the scraped site itself.…”

“…where Q Tot is the horizontal (saltation) mass flux (g cm −1 s −1 ), A is a unitless parameter (usually assumed to be equal to 1) related to supply limitation (Gillette and Chen, 2001), ρ is the density of air (g cm −3 ), g is the acceleration of gravity (cm s −1 ), u * is the wind shear velocity and u * t is the threshold shear velocity (both cm s −1 ). Q Tot is envisioned as the mass flowing past a pane one length unit wide, perpendicular to both the wind and the ground.…”

A case of extreme particulate matter concentrations over Central Europe caused by dust emitted over the southern Ukraine

“…The presence of crusts can reduce dust emission from a soil surface (Belnap and Gillette, 1997). The loss of fine soil material by wind deflation can lead to a decrease of dust production from a specific area over time (Gillette and Chen, 2001). Surface disturbances as a consequence of cultivation of soils in dry regions may lead to enhanced dust emissions.…”

Banded vegetation‐dune development during the Medieval Warm Period and 20th century, Chihuahuan Desert, New Mexico, USA

“…The dominant wind direction is from the west-southwest and is greatest in March, April, and May, with the highest average wind speed occurring in April (12.4 km/hr, 7.8 mi/hr) (Wainwright 2006). No helicoidal winds have been reported for this area (e.g., Gillette and Chen 2001). Occasional gusts can reach 145 km/ hr (90 mi/hr).…”