Impact of being evergreen or deciduous on the wood anatomy of the trees in polar regions during the warm geological period : case study from Upper Cretaceous of the James Ross Island (Antarctic Peninsula)

Změny prostředí v důsledku globálního oteplovaní a jejich následky jsou podstatnou a široce studovanou otázkou. Křídové polární ekosystémy nemají v dnešní době obdobu. Proto takové ekosystémy představují unikátní možnost pro studium extrémních prostředí a organizmů se specifickými adaptacemi na ně. Příslušné ekosystémy mohou mít klíčový význam pro pochopení možných budoucích změn na naší planetě. Diplomová práce se věnuje otázce strategie adaptace suchozemských rostlin v období pozdní křídy: stálezeleností a opadavostí. Studovaný materiál pochází z oblasti Brandy Bay a Crame Col na ostrově Jamese Rosse u Antarktického poloostrova a byl sbírán v souvislém sledu profilů od souvrství Kotick Point po souvrství Santa Marta (cenonam až kampán). Ze studovaných 55 vzorků fosilních dřev bylo vybráno a systematicky popsáno pět typických taxonů jehličnanů pro dané geologické období a oblast: Agathoxylon kellerense, Agathoxylon antarcticus, Araucarioxylon chapmanae, Podocarpoxylon multiparenchymatosum a Phoroxylon sp. Agathoxylon kellerense (vzorek číslo AN34) byl vybrán pro detailní analýzu a zjištění strategie adaptace jehličnanů na základě anatomické stavby letokruhů. Metodou stanovení strategie adaptace rostliny (procentuální zmenšení buněk; procentuální zastoupení letního dřeva; RMI; náklon CSDM křivky)...Global warming and its influence on the environment has become a popular and widespread issue. Nowadays, an analogy of a high latitude ecosystem during the greenhouse type of climate does not exist. The Cretaceous polar ecosystem gave us a unique possibility of understanding these extreme ecosystems and the specific adaptations of organisms to these conditions. Such types of ecosystem are crucial for a better understanding of possible future climate changes. This thesis focusses on the adaptation strategies of land plants during the Late Cretaceous in the Arctic peninsula. The land plants responded to these specific solar conditionals in two different ways: evergreen or deciduous. The fossil material for this study comes from Brandy Bay and Crame Col, James Ross Island, Antarctic. The material was collected in a continuous sequence from Kotic point to Santa Marta Formation (Cenomanian - Companian). A detailed and systematic analysis was performed on five out of fifty-five samples that well represented the studied region and age: Agathoxylon kellerense, Agathoxylon antarcticus, Araucarioxylon chapmanae, Podocarpoxylon multiparenchymatosum and Phoroxylon sp. Based on the detailed study of Agathoxylon kellerense (sample number AN34) wood anatomy and growth rings structure, adaptation strategies were...Institute of Geology and PaleontologyÚstav geologie a paleontologiePřírodovědecká fakultaFaculty of Scienc

Aspects of the high latitude environments in Cretaceous and Paleogene with special respect to land plants

This work is focused on the problematics of high latitudes in Cretaceous and Paleogene. The introduction describes and defines high latitude regions as well as their main characteristics nowadays. This allows one to achieve a better understanding of the substantial differences of these regions nowadays and in the geological past. The work itself then provides a brief description of the palaeographic position of the Arctic and Antarctic regions, their palaeoclimatic situations, organisms inhabiting their terrestrial and marine environments and their adaptation mechanisms. Further, a more detailed review of the land plants is presented. The last part is dedicated to the specific survival strategies of the land plants in the polar regions during the warm geological periods. On the basis of the studied literature, this work attempts to answer the questions: which strategy for adaptation to the high latitudes was used by the plants and whether being evergreen or deciduous was more effective on survival during the long and relatively warm polar nights. In conclusion, the relevance of the research of high latitude regions during the Cretaceous and Paleogene greenhouse type of climate is introduced in relation to the possible future consequences of the global warming. Key words: Cretaceous, Paleogene, land..

Impact of being evergreen or deciduous on the wood anatomy of the trees in polar regions during the warm geological period : case study from Upper Cretaceous of the James Ross Island (Antarctic Peninsula)

Global warming and its influence on the environment has become a popular and widespread issue. Nowadays, an analogy of a high latitude ecosystem during the greenhouse type of climate does not exist. The Cretaceous polar ecosystem gave us a unique possibility of understanding these extreme ecosystems and the specific adaptations of organisms to these conditions. Such types of ecosystem are crucial for a better understanding of possible future climate changes. This thesis focusses on the adaptation strategies of land plants during the Late Cretaceous in the Arctic peninsula. The land plants responded to these specific solar conditionals in two different ways: evergreen or deciduous. The fossil material for this study comes from Brandy Bay and Crame Col, James Ross Island, Antarctic. The material was collected in a continuous sequence from Kotic point to Santa Marta Formation (Cenomanian - Companian). A detailed and systematic analysis was performed on five out of fifty-five samples that well represented the studied region and age: Agathoxylon kellerense, Agathoxylon antarcticus, Araucarioxylon chapmanae, Podocarpoxylon multiparenchymatosum and Phoroxylon sp. Based on the detailed study of Agathoxylon kellerense (sample number AN34) wood anatomy and growth rings structure, adaptation strategies were..

Impact of being evergreen or deciduous on the wood anatomy of the trees in polar regions during the warm geological period : case study from Upper Cretaceous of the James Ross Island (Antarctic Peninsula)

Global warming and its influence on the environment has become a popular and widespread issue. Nowadays, an analogy of a high latitude ecosystem during the greenhouse type of climate does not exist. The Cretaceous polar ecosystem gave us a unique possibility of understanding these extreme ecosystems and the specific adaptations of organisms to these conditions. Such types of ecosystem are crucial for a better understanding of possible future climate changes. This thesis focusses on the adaptation strategies of land plants during the Late Cretaceous in the Arctic peninsula. The land plants responded to these specific solar conditionals in two different ways: evergreen or deciduous. The fossil material for this study comes from Brandy Bay and Crame Col, James Ross Island, Antarctic. The material was collected in a continuous sequence from Kotic point to Santa Marta Formation (Cenomanian - Companian). A detailed and systematic analysis was performed on five out of fifty-five samples that well represented the studied region and age: Agathoxylon kellerense, Agathoxylon antarcticus, Araucarioxylon chapmanae, Podocarpoxylon multiparenchymatosum and Phoroxylon sp. Based on the detailed study of Agathoxylon kellerense (sample number AN34) wood anatomy and growth rings structure, adaptation strategies were..

A review of the Hirmeriellaceae (Cheirolepidiaceae) wood

International audienceSummary The Hirmeriellaceae are an extinct family of Mesozoic conifers. Their foliage has been described in the genera Brachyphyllum , Frenelopsis , Pseudofrenelopsis , etc., while their pollen corresponds to the genus Classopollis , the male cones to e.g. Classostrobus or Tomaxellia and the female scales were named Hirmeriella and Paraucaria , for example. Reproductive structures are necessary for a definite identification of the family. Such fossils are rarely found in connection with mature secondary xylem. As a result, very little is known about the wood anatomy of the Hirmeriellaceae. This work reviews available evidences, either from connections between wood and reproductive structures typical for the Hirmeriellaceae or from associations of such fossils within Mesozoic rocks. Connection cases are rare and are reported only for the Cretaceous and for genera Frenelopsis and Pseudofrenelopsis . Association cases are more numerous; however, they are also poorly distributed in time, being reported mostly from two intervals only, the latest Triassic–earliest Jurassic and the Early Cretaceous. Wood data are also poorly distributed taxonomically with most of them being from the frenelopsids. The fossil genera Agathoxylon , Brachyoxylon , Protocupressinoxylon and Protopodocarpoxylon were used for wood fossils which are more or less safely related to the Hirmeriellaceae. However, only the first two seem to have been rightly used, the first usually for juvenile or small diameter wood, the second for more mature wood. Even if there seems to be a privileged link between Brachyoxylon and the Hirmeriellaceae, it cannot be said to be exclusive