Diversity, functionality and evolution of medullosan seed ferns: Vegetation-climate interactions in a seasonally dry in-situ habitat of early Permian age

该项目的重点是早二叠世种子植物的生态和进化动力学及其与晚古生代气候变化的关系。这一时期的特点是广泛的冰川作用，相当于现在的冰河时代，而在二叠纪早期的冰室温室过渡是特别感兴趣的。与石炭纪的主要冰川期相比，这一时期的大气CO2分压数据存在相当大的差距。在古气候研究中，植物化石起着关键作用，因为它们提供了关于降水、温度和大气中CO2含量的可测量参数。然而，到目前为止，这些都是从孤立的植物器官，这限制了他们的古生态学意义。在广泛分布的二叠纪种子植物中，髓生植物特别提供了高于平均水平的水传导潜力，与现代阔叶树相当。因此，它们可以被认为是气候敏感的，因此有希望进行古气候研究。1）调查和重建切姆尼茨二叠纪地区髓管动物的功能，2）全植物水力学模拟，以促进植物古气候代用指标的优化方法，（3）评价了一种计算早二叠世大气CO2分压的新方法。化石来自切姆尼茨化石森林，一个就地保存的，早二叠世（2.91亿年）的绿洲状栖息地，在那里可以研究生物与环境之间的关系。该网站提供了一个世界范围内显着的髓管动物的多样性，占主导地位，这是密集的潮湿的植物群落，暴露于季节性干旱。由于被火山沉积物迅速掩埋，一些树木被发现仍然直立，因此可以通过考虑各种特定地点的参数（如古气候，土壤和植被）来研究它们的生长地点。三种几乎完全保存的髓化石将被研究，包括从根到冠的各种器官。特殊的功能，迄今没有反映解剖细节建议与现代苏铁，最近的生活亲属髓。这包括一个生态相关的水储存和供应系统的形式，一个中空的圆柱形，水平管胞网络，以及根结构，建议比较珊瑚状，共生活性苏铁根。关于植物水传导潜力的所有可测量参数都将根据其古生态意义的既定计算方法加以确定和评价。这些解剖数据的水传导率将被用来测试一个有前途的方法建模的CO2分压的气氛中，替代常用的方法的基础上气孔密度的叶子。

The project focuses on the ecological and evolutionary dynamics of early Permian seed plants and their relationships to climate change in the late Palaeozoic. This period was characterised by extensive glaciation, comparable to the present Ice Age, whereas the Icehouse-Greenhouse transition in the early Permian is of particular interest. In contrast to the main glaciation phase in the Carboniferous, this period shows a considerable data gap regarding the CO2 partial pressure of the atmosphere. In palaeoclimate research, fossil plants play a key role, as they provide measurable parameters on precipitation, temperature, and CO2 content of the atmosphere. However, so far, these have only been obtained from isolated plant organs, what limits their palaeoecological significance. Among the widespread Permian seed plants, medullosans in particular offer an above-average water conduction potential quite comparable to that of modern broadleaved trees. Accordingly, they can be recognised as climate-sensitive and thus promising for palaeoclimate studies.Aims of the project are: 1) Investigating and reconstructing functionality of medullosans at their Permian type locality of Chemnitz, 2) whole-plant hydraulic modeling in order to contribute to optimising methods of plant palaeoclimate proxies, 3) evaluating a novel approach for the calculation of the CO2 partial pressure of the early Permian atmosphere.The fossils originate from the Chemnitz Fossil Forest, an in-situ preserved, oasis-like habitat of early Permian age (291 myrs), in which relationships between organisms and their environment can be investigated. The site offers a worldwide remarkable diversity of medullosans, dominating this dense hygrophilous plant community that was exposed to seasonal droughts. Due to rapid burial by volcanic deposits, some of the trees were found still standing upright enabling to study them at their places of growth by taking into account a variety of site-specific parameters such as palaeoclimate, soil, and vegetation.Three almost completely preserved medullosans will be investigated including various organs from the roots to the crown. The function of special, hitherto not reflected anatomical details suggests the comparison with modern cycads, the nearest living relatives of the medullosans. This includes an ecologically relevant water storage and supply system in the form of a hollow-cylindrical, horizontal tracheid network, as well as root structures that suggest a comparison with coralloid, symbiotically active cycad roots. All measurable parameters on the water conductivity potential of plants are to be determined and evaluated in the context of established calculation methods with regard to their palaeoecological significance. These anatomical data on water conductivity will be used to test a promising approach of modeling the CO2 partial pressure of the atmosphere, alternatively to the commonly applied method based on stomata density of leaves.