#PACKRAT ARIZONA SERIES#

The development of radiocarbon dating using the tandem accelerator mass spectrometer (TAMS) allows direct dating of very small samples. Radiocarbon dating of packrat midden assemblages from a single cave or from several nearby sites in a homogeneous local area can yield a detailed, local vegetation chronology for many thousands of years from within 30-50 m on the rocky slopes in front of the dry rock shelters 3,4. In most of the modern deserts, woodland or forest communities were present during the last glacial age, the Wisconsin. LATE QUATERNARY ECOLOGY, CLIMATOLOGY, AND BIOGEOGRAPHY OF THE NORTHERN CHIHUAHUAN DESERT FROM FOSSIL PACKRAT MIDDENSAnalyses of well-preserved plant remains from ancient packrat (Neotoma) middens have yielded much information on the history of vegetation, fauna and climate from the more arid portions of North America over the past 40,000 years 1,2. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author. Digital access to this material is made possible by the University Libraries, University of Arizona. appears to have been due, at least in part, to increasing winter temperatures.Д¬opyright В© is held by the author. The appearance of many desertscrub species around 5000-4000 yr B.P.

Bioclimatic envelopes for C4 grasses indicate winter temperatures were no more than 4.5вњ¬ colder than present and summer temperatures no more than 4.4вњ¬ colder during late Pleistocene, while summer precipitation was reduced by no more than 50%.

#PACKRAT ARIZONA SERIES#

Few middens date from the early to middle Holocene, while 35 middens from the late Holocene detail increasingly aridity.Bioclimatic envelopes were also applied to packrat midden series from the USA-Mexico borderlands.

After ~15,410 cal yr B.P., Pinus edulis declined in abundance and disappeared briefly at 13,925 cal yr B.P., coincident with other evidence for BГёlling-AllerГёd aridity, and then rebounded briefly during the Younger Dryas. This site also supported summer-flowering C4 annuals and grasses, indicating abundant summer rains and relatively warm temperatures. Between 36,200-15,410 cal yr B.P., rocky areas above playa lakes supported Pinus edulis, Juniperus osteosperma, Juniperus cf. midden record was also developed from the Peloncillo Mountains along the Arizona-New Mexico-Mexico border. The late Holocene was marked by arrival of Chihuahuan Desert scrub as vegetation became modern in character. Pinus edulis and Juniperus scopulorum had become rare or disappeared. This summer-flowering understory, characteristic of modern desert grasslands, suggests at least moderate late Pleistocene summer precipitation. coahuilensis and an understory of C4 annuals and grasses. Plant macrofossil and pollen assemblages from nine middens indicate late Pleistocene vegetation along pluvial lake margins consisted of open pinyon-juniper communities dominated by Pinus edulis, Juniperus scopulorum, Juniperus cf. The focus of this dissertation is the reconstruction of late Quaternary ecology, climatology, and biogeography of the northern Chihuahuan Desert.A new packrat midden chronology from Playas Valley, NM is the first installment of an effort to reconstruct paleovegetation and paleoclimate in the U.S.A.-Mexico Borderlands. A conspicuous gap in packrat midden coverage, however, exists for this area and paleovegetation data is scarce. The northwestern Chihuahuan Desert along the U.S.A.-Mexico border contains a rich mosaic of vegetation with high levels of biodiversity.

Packrat arizona