Wells P V, Berger R
Science. 1967 Mar 31;155(3770):1640-7. doi: 10.1126/science.155.3770.1640.
Seventeen ancient wood-rat middens, ranging in radiocarbon age from 7400 to 19,500 years and to older than 40,000 years, have been uncovered in the northeastern, north-central, southeastern, and southwestern sectors of the Mohave Desert. Excellent preservation of macroscopic plant materials (including stems, buds, leaves, fruits, and seeds) enables identification of many plant species growing within the limited foraging range of the sedentary wood rat. An approximately synchronous zonal differentiation of vegetation in response to a gradient of elevation on limestone in the northeastern Mohave Desert is apparent from the macrofossil evidence, preserved in wood-rat middens and ground-sloth coprolites, covering a time span bracketed by radiocarbon ages of about 9000 and 10,000 years. XerophilQus juniper woodlands descended to an elevation of 1100 meters, some 600 meters below the present lower limit of woodland (1700 meters) in the latitude of Frenchman Flat. But desert or semidesert shrubs coexisted with the woodland trees throughout much of the span of elevation corresponding to the pluvial lowering of the woodland zone, and the more mesophytic phase of pinyonjuniper woodland was evidently confined to montane habitats at elevations above 1500 meters. Joshua trees, accompanied by desert shrubs, prevailed down to about 600 meters at Gypsum Cave, Nevada, but only the shrubs of the existing warm-desert vegetation occurred at 530 meters near Rampart Cave, Arizona. Pleistocene middens from the southeastern Mohave Desert record a relatively large downward shift of the pinyon-juniper woodland zone, paralleling the remarkably low minimum elevation of the existing woodland zone in that area. The macrofossil evidence speaks for former continuity of the many disjunct stands of woodland vegetation in the Mohave Desert region, at least along the higher divides connecting most of the ranges. However, there is no macrofossil evidence of pluvial continuity of range for the more mesophytic, montane, coniferous-forest zone of ponderosa pine or white fir now occupying islands of relatively mesic environment on the highest mountains of the region. On the contrary, the uneven stocking of the lofty mountains of the Mohave Desert with mesephytic or boreal species and the trend toward endemism suggest a long history of isolation.
在莫哈韦沙漠的东北部、中北部、东南部和西南部地区，已发现了17处古代林鼠 midden，其放射性碳年代范围从7400年到19500年，还有超过40000年的。宏观植物材料（包括茎、芽、叶、果实和种子）的出色保存使得能够识别出许多生长在定居林鼠有限觅食范围内的植物物种。从保存在林鼠 midden 和地懒粪便化石中的宏观化石证据可以明显看出，在莫哈韦沙漠东北部的石灰岩上，植被随着海拔梯度出现了大致同步的地带性分化，其时间跨度由放射性碳年代约9000年到10000年界定。旱生杜松林地下降到了海拔1100米，比弗伦奇曼弗拉特纬度地区目前林地的下限（1700米）低约600米。但在与林地地带因多雨而降低相对应的大部分海拔范围内，沙漠或半沙漠灌木与林地树木共存，而矮松 - 杜松林地的中生阶段显然局限于海拔1500米以上的山地栖息地。约书亚树与沙漠灌木相伴，在内华达州石膏洞一直延伸到约600米处，但在亚利桑那州壁垒洞附近530米处只有现有的暖沙漠植被中的灌木。来自莫哈韦沙漠东南部的更新世 midden 记录了矮松 - 杜松林地地带相对较大的向下移动，这与该地区现有林地地带极低的最低海拔相一致。宏观化石证据表明，莫哈韦沙漠地区许多分散的林地植被林分以前是连续的，至少沿着连接大部分山脉的较高分水岭是连续分布的。然而，对于现在占据该地区最高山脉相对湿润环境岛屿的中生、山地、针叶林地带（黄松或白云杉），没有宏观化石证据表明其在多雨时期的山脉连续性。相反，莫哈韦沙漠高山上中生或北方物种的分布不均以及特有化趋势表明其有着长期的隔离历史。
