Elevation-induced climate change as a dominant factor causing the late Miocene C4 plant expansion in the Himalayan foreland

Thursday, 18 December 2014
Haibin Wu1, Zhengtang Guo1, Joel Guiot2, Christine Hatte3, Changhui Peng4, Yanyan Yu1, Junyi Ge1, Qin Li1, Aizhi Sun1 and Deai Zhao1, (1)Key Laboratory of Cenozoic Geology and Environment, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, China, (2)CEREGE, Aix-en-Provence Cedex, France, (3)LSCE Laboratoire des Sciences du Climat et de l'Environnement, Gif-Sur-Yvette Cedex, France, (4)University of Quebec at Montreal UQAM, Montreal, QC, Canada
During the late Miocene, a dramatic global expansion of C4 plant distribution occurred with broad spatial and temporal variations. Although the event is well documented, whether subsequent expansions were caused by a decreased atmospheric CO2 concentration or climate change is a contentious issue. In the present study, we used an improved inverse vegetation modeling approach that accounts for the physiological responses of C3 and C4 plants to quantitatively reconstruct the paleoclimate in the Siwalik of Nepal based on pollen and carbon isotope data. We also studied the sensitivity of the C3 and C4 plants to changes in the climate and the atmospheric CO2 concentration. We suggest that the expansion of the C4 plant distribution during the late Miocene may have been primarily triggered by regional aridification and temperature increases. The expansion was unlikely caused by reduced CO2 levels alone. Our findings suggest that this abrupt ecological shift mainly resulted from climate changes related to the decreased elevation of the Himalayan foreland.