Reconstruction of the Late Pleistocene to Late Holocene vegetation transition using packrat midden and pollen evidence from the Central Mojave Desert

ABSTRACT The Mojave Desert of the American West is characterized by plant species that reflect a unique mixture of winter precipitation and summer monsoon climate. Currently, the Mojave Desert experiences a strong summer monsoonal pattern with weak winter precipitation. Data from pollen and packrat midden analyses have revealed a history of Mojave Desert vegetation during the transition from the late Pleistocene to late Holocene (~17500 Cal. years B.P. to ~ 1200 Cal. years B.P.) that highlight a summer dominated monsoonal pattern, similar to those in the greater American Southwest. We compare pollen data from a lava tube in the Cima volcanic field, located in south-central region of the Mojave Desert, with plant macrofossil data from several woodrat midden localities in the region. The record for the Cima volcanic field reveals a vegetation history spanning the last ~ 8300 Cal. years B.P., with data from ancient woodrat middens detailing the record from ~17500 Cal. years B.P. to 7,800 Cal. years B.P. A Bryson macro-physical climate model for the transition from the late Pleistocene to the Late Holocene was created and compared to our findings to assess possible relationships between climatic variations and the arrival of diagnostic plant species within the Mojave Desert.摘要 美国西部的莫哈韦沙漠（Mojave Desert）的植被类群兼具冬季降水与夏季季风气候的独特混合特征，这是其典型标识。当前，莫哈韦沙漠呈现出显著的夏季季风格局，冬季降水则相对微弱。通过花粉与林鼠贮巢（packrat midden）分析获得的数据，揭示了晚更新世晚期至全新世晚期（约17500校正距今年（Cal. years B.P.）至约1200校正距今年（Cal. years B.P.））期间莫哈韦沙漠的植被演化历史，该历史凸显了以夏季为主导的季风模式，这与美国更大范围西南部的季风模式高度相似。本研究将采自莫哈韦沙漠中南部锡马火山场（Cima volcanic field）一处熔岩管（lava tube）的花粉数据，与该区域内多个林鼠贮巢点位的植物大化石（plant macrofossil）数据进行了对比分析。锡马火山场的植被记录覆盖了过去约8300校正距今年的演化历程，而古代林鼠贮巢的数据则详细记录了约17500校正距今年至7800校正距今年的植被变化。我们构建了晚更新世晚期至全新世晚期的布莱森宏观物理气候模型（Bryson macro-physical climate model），并将其与本研究的观测结果进行对比，以评估气候变异与莫哈韦沙漠特征植物类群出现之间的潜在关联。