Science. 1979 May 18;204(4394):701-10. doi: 10.1126/science.204.4394.701.
Plant macrofossils in ancient packrat middens document the presence of woodland communities in most of the present Chihuahuan, Sonoran, and Mohave deserts in the southwestern United States during the late Wisconsinan (22,000 to 11,000 years before present by radiocarbon dating). Warm desert species were common in the woodlands at lower elevations and mixed conifer and subalpine forests were present at high elevations. Inferred mild, wet winters and cool summers produced unusual plant and animal associations compared to those of today. Montane communities acquired modern aspects and more mesophytic species disappeared from lower woodlands about 11,000 years ago. Early Holocene xeric woodlands and an inferred winter precipitation regime persisted until about 8000 years ago. The present circulation patterns, rainfall regimes, and biotic distributions probably formed as a result of the melting of the continental ice sheets. Southwestern communities appear to have responded quickly to climatic changes compared to the gradual responses of central and eastern United States forest communities.
古代囊鼠丘中的植物大化石记录表明，在距今 22000 到 11000 年前的威斯康星晚期（放射性碳定年法），美国西南部的大部分奇瓦瓦、索诺兰和莫哈韦沙漠中存在林地社区。在较低海拔地区的林地中，温暖的沙漠物种很常见，而在高海拔地区则存在混合针叶林和亚高山森林。推断温和、潮湿的冬季和凉爽的夏季与今天的气候相比，产生了不寻常的植物和动物组合。大约 11000 年前，山地社区获得了现代特征，而较低林地中的更多中生植物物种消失了。大约 8000 年前，早全新世干旱林地和冬季降水模式持续存在。目前的环流模式、降雨模式和生物分布可能是由于大陆冰盖融化而形成的。与美国中部和东部森林社区的逐渐响应相比，西南社区似乎对气候变化的反应更快。
