North American Deserts

1
North American Deserts

• Mohave
• Sonoran
• Chihuahuan

2
General Facts

• Wide elevational span (-86 m Death Valley
  1525 m Chihuahuan)
• Latitude (22º 36.5º N)
• Warm deserts because precipitation occurs
  primarily as rain. The Great Basin is a cold
  desert because 60 of its precipitation occurs as
  snow.

3
Physiography
4
Physiographic Features

• Playa lakes Lakes that are dry for at least
  part of the year. Form when runoff from
  surrounding mountains accumulates in basins.
• Alluvial fans cone-like depositions of sediment
  extending out from mountains onto the valleys.
• Bajada Coalesced alluvial fans. Soil
  conditions vary along a bajada. Coarse-textured
  soils found at upper portions of the bajada, and
  fine-textured soils found at lower ends.

5
Soils

• Caliche
• Hard pan soil horizon caused by cementing of
  calcium carbonates, silica, and/or iron compounds
• Forms a water-impervious layer
• Can be very thick (up to 90 m)
• Can be at the surface or buried
• Can influence vegetation (e.g. Creosote bush
  (Larrea tridentata) requires high-calcium,
  gravelly soils with a relatively deep caliche
  layer)

6
Soils

• Bajada soils
• Upper bajadas have higher proportion of large
  soil particles
• Salinity gradient from upper to lower bajada with
  greater salinity at the upper bajada
• Diversity of vegetation decreases from upper to
  lower bajada
• Erosional features such as arroyos and rills can
  modify vegetation and soil patterns on a bajada.

7
Climate
Mohave
Sonoran
Chihuahuan
Sonoran Desert is generally the warmest. Due
primarily to being at the lowest elevation Mojave
Desert has the highest absolute
temperatures. Again largely due to low
elevations. Seasonality of rainfall varies.
8
Seasonality of Precipitation