Gran Desierto de Altar - Flora

Flora

See also: List of plants by common name (Sonoran Desert)

Vegetation assemblages of the Gran Desierto are typical of the lower Sonoran Desert with a marked difference in vegetation type and density with location. Large areas of the southern and eastern sand sea, especially near the margins, have a moderately dense (up to 20%) cover of perennial low shrubs and herbs such as bursage (Ambrosia dumosa) and longleaf jointfir (Ephedra trifurca) with creosote bush (Larrea tridentata) in areas of thin sand cover. Palo Verde/Acacia/Ocotillo communities occur on alluvial slopes on the northern side of the sand sea, particularly in arroyos and washes. Felger estimated total vegetation cover at 15% in the star dunes and about 10% in the low transverse or crescentic dunes areas. These percentages are substantially greater than in most active dune fields where vegetation covers of 15% are more typical .

Several teams (e.g. Van Devender et al. and Hall et al. ) have examined the nests (middens) built by pack rats as a proxy for ancient vegetation regimes. All have concluded that the Gran Desierto has been a refugia for desert plants since at least the late Pleistocene. The Gran Desierto has served as a refuge for most dominant Mojave Desert plant species during cooler pluvial epochs as well. Van Devender has also reported C14 dates for a midden from the Tinajas Altas Mountains showing assemblages of Juniper and Joshua trees coexisting with contemporary Gran Desierto flora and fauna more than 43,000 years before present. Although midden studies do not provide information beyond the late Pleistocene, they do indicate that, in gross form, the climate of the Gran Desierto as recorded by plant communities has been desert-like since at least the peak of the Wisconsinan glaciation.