干旱区生态环境知识资源中心

Eighty-two plant and 26 small vertebrate taxa were identified from four radiocarbon dated woodrat (Neotoma sp.) midden samples from a rock crevice at 655 m elevation on Picacho Peak, Pinal Co., Arizona. A late Wisconsin (I 1,100 to 13,170 YBP) pinyon-juniper-oak woodland dominated by Pinus monophylla (singleleaf pinyon) and Juniperus cf. osteosperma (Utah juniper) and J. erythrocarpa/monosperma (redberry/oneseed juniper) shifted to a more xeric juniper-oak woodland/chaparral in the early Holocene (9,420 to 10,280 YBP). Extralocal species that no longer live on Picacho Peak were 29.9% in the late Wisconsin and 20.1% in the early Holocene with the greatest changes in long-lived trees, shrubs, and succulents. The biogeographic and taxonomic significance of Scaphiopus hammondi (western spadefoot) and the ecological adaptability of Phrynosoma platyrhinos (desert horned lizard), Micranthe whitneyi (elf owl), and Neotoma cf. albigula (white-throated woodrat) are discussed. All taxa in the vertebrate fauna are widespread in desertscrub and desert-grassland, still occur in the area, and enter woodlands only at the upper or northern edges of their ranges. The typical inhabitation of woodlands by these vertebrates and anomalous associations in the flora probably reflect the expansion of equable climates that now characterize ecotonal habitats during the late Wisconsin glacial.