Arcuate
Dune Patterns in Southern New Mexico
The Jornada
Experimental Range,
located approximately 40 km north, northeast of Las Cruces, New Mexico,
has numerous geomorphologic features that are typical to arid/semi-arid
regions. One of these features, arcuate or parabolic dunes, is frequently located in
transitional zones between desertified areas and grassland. As the name implies these dunes are arc
shaped and consist of three separate zones that repeat in sequence as one
pattern; the desertified zone, the dune zone composed of shrubs, and the
grassland zone. This pattern of
desertified area, dune area, and grassland repeats in a southwest to northeast
trend until further up on the piedmont slope where hydrologic features control
the landscape.
According to surveyor notes
from the middle 1800’s to the early 1900’s the area was predominantly covered
with perennial grasses (Gibbens et al). Now the area is predominantly covered with
creosote and mesquite shrubs. The change
coincides with the introduction of intense cattle grazing during the late
1800’s and early 1900’s. The arcuate dunes lie on the piedmont slope of the San Andreas
Mountain which consists of limestone
parent material. The basin floor
contains ancestral Rio Grande
river sediment.
The arcuate
dune is part of a patterned sequence (Fig. 1).
The first section is an area of eroded, silty
soils barren of most vegetation (Figs. 2 and 3). It is characterized by gullies and sheet
erosion indicating that it is a prominent run-off zone. As erosion migrates upslope scarplets form that range in height from approximately 2cm
to 1 meter (Fig. 4). The arcuate dune is upslope of the scarplet
and consists of red aeolian sand that has blown in
from the adjacent basin floor. The sand has buried the silty
alluvial sediments washed down from limestone bedrock to the east (Figs. 5a,
5b). In front of the arcuate
dunes are areas of grass cover (Fig. 6).
The dunes form a dam behind which run-in water and nutrients accumulate.
Figure 1. Aerial photograph of
Jornada landscape
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This landscape
occurs in southern New Mexico
has well as other arid/semi-arid regions of the world.
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Gobi
desert of northwest China.
Eroded, barren
surface in front of
coppice dunes. Picture taken during
a sandstorm.
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Gobi
desert of northwest China.
Sand
dunes encroaching into grassland.
This area is used
for camel grazing.
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South of the
equator; southwestern
Kenya. Grassland with
shrubs
encroaching.
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South of the
equator; southwestern
Kenya. Eroded
soil in front of scarplets.
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References
Gibbens, R.P., McNeely,
R.P., Havstad, K.M., Beck, R.F., Nolen, B.,
2005. Vegetation changes in the Jornada Basin
from 1858 to 1998. Journal of Arid Environments 61, 651-668.
Additional Reading
Dunkerley, D.L., Brown, K.J.,
1999. Banded vegetation near Broken
Hill, Australia:
significance of surface roughness and soil
Physical
properties. Cantena 37, 75-88.
Ludwig, J.A.,
Wilcox, B.P., Breshears, D.D., Tongway, D.J., Imeson, A.C.,
2005. Vegetation patches and runoff-erosion as
Interacting ecohydrological processes in semiarid landscapes.
Ecology 86, 288-297.
Monger, H.C., Bestelmeyer, B.T. (in press) The
soil-geomorphic template and biotic change in deserts.
Peterson, F.F.,
Fleischmann M.C., Bohmont, D.W. Landforms of the Basin and Range Province: defined for Soil Survey.
Nevada
Agricultural Experimental Station. Technical Bulletin
28. January 1981.
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