Development of vegetation in the Central Mojave Desert of California during the late quaternary

Vegetation analysis of 47 Neotoma (packrat) middens from the core of the central Mojave Desert of California reveal changes in desert plant community composition over the last ca. 24,000 years BP, one of the lowest and most and locations in North America. Habitat currently dominated by Mojave Desert Larrea tridentata (creosote bush) was occupied prior to ca. 11,500 years BP by Pinus monophylla (pi (n) over tilde on), Juniperus osteosperma (Utah juniper), Purshia mexicana (bitterbush), Cercocarpus ledifolius (mountain mahogany), and Prunus fasciculata (desert almond) woodland above 1000 m. P monophylla-Juniperus woodland was widespread over the southern and central Mojave Desert. However, less than 150 km north of the central Mojave, J. osteosperma steppe dominated the landscape. Paleoecologic records spanning latitude 35degreesN ca. 37degreesN document a biogeographic boundary between milder, moister environments to the south and the colder, drier environments to the north. At elevations <1000 m desert scrub species of Lycium cooperi (wolfberry), Salvia mojavensis (Mojave sage) and the mesophytic Prosopis juliflora (mesquite) occurred near the shore of pluvial Lake Mojave from ca. 8810 to 8430 years BP. Larrea is not recorded on the xeric carbonate substrates (605 m) until ca. 6990 years BP, then took over 2000 years to dominate the regional landscape. Modem vegetation associates such as Thamnosma montana (desert rue) and Atriplex confertifolia (shadscale) were established by ca. 4500 years BP. Late Holocene vegetation changes document Neoglacial cooling and wetter conditions than today between ca. 3490 and 2640 years BP, paralleling the regional pluvial lake highstands and marsh deposit records. Decreases of mesophytic Mojave Desert associates in the Granite Mountains suggest climates similar to today's aridity between ca. 1970 and 1440 years BR Mesophytic species increase in middens dating between ca. 1390 and 700 years BP at higher elevation sites; during the same time Prosopis occurs at lower elevation sites. (C) 2004 Elsevier B.V. All rights reserved.