Middle Devonian Archaeopteridales and their role in the evolution of early forest ecosystems

在泥盆纪(大约4亿-3.6亿年前)，从最初的小型草本植物逐渐发展到末期的郁闭林。森林被认为是生物多样性的中心，也是碳汇，建立这种生态系统对地球系统意义重大。直到最近，第一批森林树木被认为是泥盆纪晚期的始祖鸟(始祖鸟属)。它们的树干类似于活针叶树的树干，树枝多叶，但带有孢子繁殖。最近，假孢子植物被证明在中泥盆世形成了森林。这些植物的树干与树蕨类植物有一些相似之处，但树枝上缺乏扁平的网状叶。与这些假孢子虫植物同时代的是始祖蕨属的早期形式，名为斯瓦尔巴迪亚。人们对早期始祖鸟的建筑、形态和解剖知之甚少。该项目将研究这些植物的新材料，这些材料来自与中泥盆世伪孢子树相同的沉积物。根据这种材料，早期始祖鸟的“全植物”概念将被创造出来。目前的理论表明，树叶是随着大气中二氧化碳的减少而进化的。这项调查的结果将使人们能够直接比较在从无叶森林向有叶森林过渡期间竞争优势的两种植物，以及更好地了解它们与种子植物的关系。

During the Devonian era (approximately 400-360 million years ago) there was a progressive development from small herbaceous plants at the beginning to canopied forests at the end. Forests are well regarded as centres of biodiversity, as well as carbon sinks, and the establishment of such ecosystems were of great significance to the Earth System. Until recently the first forest trees were thought to be archaeopteridalean progymnosperms (genus Archaeopteris) during the Late Devonian. These had trunks which are similar to those of living conifers, and leafy branches, but reproduced with spores. More recently pseudosporochnalean plants have been shown to have formed forests in the Mid Devonian. These plants had trunks with some similarity to treeferns, yet the branches lacked flattened webbed leaves. Contemporaneous with these pseudosporochnalean plants were early forms of archaeopteridalean, named Svalbardia. Little is known about the architecture, morphology and anatomy of the early archaeopteridaleans. This project will study newly available material of these plants from the same deposits as the Mid Devonian pseudosporochnalean trees. From this material 'whole-plant' concepts of the early archaeopteridaleans will be created. Current theories suggest that leaves evolved in response to a drop in atmospheric CO2. The results of this investigation will allow direct comparison of the two whole plants which were competing for dominance during the transition from non-leafy to leafy forests, as well as better understanding of their relationships to seed plants.