The characterization of the Permian Cathaysia Flora based on fossil cuticles

二叠纪见证了中生代最极端的气候转变之一，从早二叠世的深冰库条件到晚二叠世的温室状态。冈瓦纳大陆与欧亚大陆在晚宾夕法尼亚世的碰撞导致了古大陆泛大陆的形成，对气候产生了重大影响。华夏植物区系是晚古生代出现的四大植物区系之一。华夏植物群包括几个在欧美也是已知的成分，但也包括一些特有的分类群。由于华夏植物区系的分类主要是基于宏观形态学的标准，并且分类群之间的关系往往不清楚，因此，对华夏植物群进行详细的研究对于更好地了解其与其他植物区系的关系是必要的。表皮分析不仅可以更精确地确定和划分个体分类群，而且还可以根据生物学标准，即表皮解剖学，提供重要的古生态和古气候信息。该项目将以山西西北部的爬楼沟剖面为重点，该剖面目前被普遍认为是华夏植物群的标准参考剖面。这一连续出露的剖面包括几个具有良好角质层保存的植物层位，从上石炭统开始，一直延伸到二叠纪-三叠纪界线。该项目包括从连续的角质层进行全面的角质层研究，以便：（1）在生物学标准的基础上，对各分类群进行合理的定义、划界和生态学表征;（2）根据气孔密度（SD）和气孔指数（SI）重建各演替群丛的古大气CO2水平;（3）将华夏植物群与相似古纬度的欧美植物群进行比较。我们期望，这一项目将导致更好地了解华夏植物群及其与其他时间相当的古（亚）热带植物群的关系。

The Permian witnessed one of the most extreme climate transitions of the Phanerozoic, from deep icehouse conditions in the Early Permian to a greenhouse state by the Late Permian time. The collision of Gondwana with Eurasia in the Late Pennsylvanian resulted in the formation of thesupercontinent Pangea, which had a significant impact on the climate. Cathaysia is one of the four floral provinces that emerged during the late Paleozoic. The Cathaysia flora comprises several elements that are also known from Euramerica, but also a number of endemic taxa. As thetaxonomy is primarily based on macromorphological criteria and relationships of taxa often remain unclear, detailed studies of the Cathaysia flora are necessary for a better understanding of its relationships to the other floral provinces. Cuticular analysis not only allows a much more precisedefinition and delimitation of individual taxa, but it also provides important information on the palaeoecology and palaeoclimate on the basis of biological criteria, i.e. the epidermal anatomy. This project will focus on the Palougou section in NW-Shanxi, which is now generally regarded as a standard reference section for the Cathaysia flora. This continuously exposed section includes several horizons with plants with good cuticle preservation and starts in the Upper Carboniferous and runs up to the Permian-Triassic boundary. This project embraces a comprehensive study of cuticles from the successive cuticle-bearing horizons in order to: (1) establish a sound definition, delimitation, and ecological characterization of individual taxa on the basis of biological criteria, (2) reconstruct palaeoatmospheric CO2 levels of the successive associations based on stomatal densities (SD) and indices (SI), and (3) compare Cathaysia floras with Euramerican floras from thesimilar palaeolatitudes. We anticipate that this project will lead to a much better understanding of the Cathaysia flora and its relations to other time-equivalent palaeo(sub)tropical floras.