Cenozoic xeromorphic vegetation in China and its spatial and temporal development in connection with global changes

Remarkable angiosperm evolution and significant vegetation changes took place during the Cenozoic on earth. Specifically, Neogene is a crucial period in forming the framework of the current vegetation and in restructing earth ecosystem after the Eocene–Oligocene “greenhouse-icehouse” climate transition. Under the background of global changes, regional vegetation in China was synchronously developed. Some local changes had made extensive influences, such as the topographic changes, especially the uplift of the Qinghai-Tibet Plateau, and the changes in seasonal atmospheric circulation and precipitation, i.e., the initiation and evolvement of Asian monsoon system, along with other geographic changes in land and sea. The expansion of xeromorphic vegetation, represented by forest steppe, steppe and desert, played an ever-increasing role, which was closely related with the development of angiospermous xerophytes. The distributions of some representative angiospermous pollen types with their parent plants of xerophilous origination in the Cenozoic are summarized in the paper. Evidence shows that the origination and evolution of the angiospermous xerophytes underwent a series of developments, which were prompted largely by environmental variations. Pollen studies from some representative sites in China show that spatial and temporal development of Cenozoic xeromorphic vegetation is largely consistent with the global changes.