Literatura científica selecionada sobre o tema "Coniferâs, Fossil"
Crie uma referência precisa em APA, MLA, Chicago, Harvard, e outros estilos
Consulte a lista de atuais artigos, livros, teses, anais de congressos e outras fontes científicas relevantes para o tema "Coniferâs, Fossil".
Ao lado de cada fonte na lista de referências, há um botão "Adicionar à bibliografia". Clique e geraremos automaticamente a citação bibliográfica do trabalho escolhido no estilo de citação de que você precisa: APA, MLA, Harvard, Chicago, Vancouver, etc.
Você também pode baixar o texto completo da publicação científica em formato .pdf e ler o resumo do trabalho online se estiver presente nos metadados.
Artigos de revistas sobre o assunto "Coniferâs, Fossil"
1
Ram-Awatar and A. Rajanikanth. "Triassic Conifer wood from the Tiki Formation, South Rewa Basin, Madhya Pradesh, India." Journal of Palaeosciences 56 (December 31, 2007): 127–32. http://dx.doi.org/10.54991/jop.2007.63.
Texto completo da fonteResumo:
The present paper records a conifer wood from the Triassic sequence of the Tiki Formation, ~3 km NE of Tiki Village, district Shahdol, Madhya Pradesh, India. Since Triassic wood records are hardly known from India when compared to leaf fossils, the present report of podocarpean wood provides additional evidence for the existence of conifers in the otherwise pteridosperm dominated fossil flora of South Rewa Basin during the Carnian-Norian times.
2
Jordan, Gregory J., Raymond J. Carpenter, Jennifer M. Bannister, Daphne E. Lee, Dallas C. Mildenhall, and Robert S. Hill. "High conifer diversity in Oligo-Miocene New Zealand." Australian Systematic Botany 24, no. 2 (2011): 121. http://dx.doi.org/10.1071/sb11004.
Texto completo da fonteResumo:
Eight species of Podocarpaceae foliage are recognised from the late Oligocene or early Miocene Newvale site, South Island, New Zealand, and the following five new species are described: two of Dacrydium Lamb. and one each of Dacrycarpus (Endl.) de Laub., Phyllocladus Rich. ex Mirb. and Halocarpus Quinn. The latter is the first macrofossil record of this New Zealand endemic genus. All these conifers, plus Agathis Salisb., Microcachrys Hook.f. and Podocarpus Pers., co-occurred in the local vegetation at Newvale. In conjunction with prior records of macrofossils and pollen, these fossils indicate that the late Paleogene to early Neogene conifer flora of New Zealand was very diverse, with all but one of the extant genera present, together with several regionally or globally extinct genera, and multiple species of many of these genera. This fossil diversity is similar to the Paleogene fossil conifer diversity observed in south-eastern Australia (and particularly Tasmania) and in parts of North America.
3
Yao, Zhao-Qi, Lu-Jun Liu, Gar W. Rothwell, and Gene Mapes. "Szecladia new genus, a late Permian conifer with multiveined leaves from South China." Journal of Paleontology 74, no. 3 (2000): 524–31. http://dx.doi.org/10.1017/s0022336000031784.
Texto completo da fonteResumo:
A conifer from the uppermost Permian with small, helically arranged leaves is described from the Guangxi Autonomous Region and Guizhou Province of South China as Szecladia multinervia, new genus and species. The material includes both impression specimens and the first anatomically preserved Paleozoic conifer fossils from China. Shoots are irregularly branched, with small, helically arranged, multiveined leaves. Stems display an endarch eustele with abundant, dense wood. Leaf traces diverge from the stele as a single bundle that divides several times in the cortex and at the base of the leaves, forming about seven or eight parallel veins in each leaf. Szecladia is the earliest known conifer with multiveined leaves and it represents a distinctive coniferous element of the uppermost Permian Cathaysian flora in South China. Szecladia further demonstrates that conifers with wood and leaf venation suggestive of the Podocarpaceae may have evolved by the end of the Paleozoic.
4
Bomfleur, Benjamin, Christian Pott, and Hans Kerp. "Plant assemblages from the Shafer Peak Formation (Lower Jurassic), north Victoria Land, Transantarctic Mountains." Antarctic Science 23, no. 2 (2010): 188–208. http://dx.doi.org/10.1017/s0954102010000866.
Texto completo da fonteResumo:
AbstractThe Jurassic plant fossil record of Gondwana is generally meagre, which renders phytogeographic and palaeoclimatic interpretations difficult to date. Moreover, plant fossil assemblages mainly consist of impressions/compressions with rather limited palaeobiological and palaeoecological significance. We here present a detailed survey of new Early Jurassic plant assemblages from the Pliensbachian Shafer Peak Formation, north Victoria Land, Transantarctic Mountains. Some of the well-preserved fossils yield cuticle. The floras consist of isoetalean lycophytes, sphenophytes, several ferns, bennettitaleans, and conifers. In addition, three distinct kinds of conifer shoots and needles were obtained from bulk macerations. The composition of the plant communities is typical for Jurassic macrofloras of Gondwana, which underscores the general homogeneity of Southern Hemisphere vegetation during the mid-Mesozoic. Altogether, the plant fossil assemblages indicate humid and warm temperate conditions, which is in contrast to recent palaeoclimatic models that predict cool temperate climates for the continental interior of southern Gondwana during the Jurassic. However, there is no evidence for notable soil development or peat accumulation. The environmental conditions were apparently very unstable due to intense volcanic activity that resulted in frequent perturbation of landscape and vegetation, hampering the development of long-lived climax communities. Cuticles of bennettitaleans and conifers show xeromorphic features that may have been beneficial for growth in this volcanic environment.
5
Hansen, Barbara C. S. "Conifer stomate analysis as a paleoecological tool: an example from the Hudson Bay Lowlands." Canadian Journal of Botany 73, no. 2 (1995): 244–52. http://dx.doi.org/10.1139/b95-027.
Texto completo da fonteResumo:
The identification of conifer stomata in fossil pollen preparations of peat cores from the Hudson Bay Lowlands is used to determine the local presence of conifers in lieu of macrofossil analyses. The differentiation of eight conifer stomate types (Picea type, Larix laricina, Pinus sp., Abies sp., Tsuga mertensiana, Tsuga heterophylla, Chamaecyparis nootkatensis, and Thuja type) is accomplished with a key, diagrammatic stomate illustrations, photographs, and measurements. Results of fossil conifer-stomate analyses indicate that both Picea and Larix arrived locally in the Albany River area of the Hudson Bay Lowlands about 4800 BP. In the Old Man Bog area, Larix arrived earlier, about 6000 BP, but Picea arrived more than 2000 years later (3700 BP). Fossil stomate and pollen results are compared. Key words: conifer stomata, local conifer presence, Hudson Bay Lowlands.
6
Kunzmann, L., B. A. R. Mohr, and M. E. C. Bernardes-de-Oliveira. "Gymnosperms from the Lower Cretaceous Crato Formation (Brazil). I. Araucariaceae and Lindleycladus (incertae sedis)." Fossil Record 7, no. 1 (2004): 155–74. http://dx.doi.org/10.5194/fr-7-155-2004.
Texto completo da fonteResumo:
Fossil conifers from the Early Cretaceous, most likely late Aptian, Crato Formation were studied. The excellent preservation of several of those fossils allowed detailed investigations of the leaf epidermis by light microscope (LM) and by scanning electron microscope (SEM). Members of two conifer taxa were recognized: The Araucariaceae are represented by a female cone of cf. <i>Araucaria</i> spec. A juvenile cone (<i>Araucariostrobus spec.</i>) and sterile foliage shoots of <i>Brachyphyllum obesum might</i> be attributed to the Araucariaceae as well. The morpho-genus <i>Lindleycladus</i> (incertae sedis) is represented by foliage shoots. The occurrence of <i>Lindleycladus</i> is the first record of this extinct morpho-genus in the Southern Hemisphere. Anatomical features of these conifers are interpreted as adaptations to a warm seasonally dry climate. Taphonomic problems concerning these conifer remains are discussed. <br><br> Fossile Koniferen aus der unterkretazischen, höchstwahrscheinlich oberaptischen Crato Formation wurden untersucht. Die ausgezeichnete Erhaltung einiger Exemplare gestattete die Analyse von Blattepidermen mittels Licht- und Rasterelektronen-mikroskop. Vertreter zweier Koniferentaxa wurden nachgewiesen: Araucariaceae kommen mit einem weiblichen Zapfen von cf. <i>Araucaria spec</i>. vor. Ein juveniler Zapfen (<i>Araucariostrobus spec</i>.) und sterile Zweige mit der Beblätterung der Morpho-Species <i>Brachyphyllum obesum</i> werden unter Vorbehalt ebenfalls zu den Araucariaceae gestellt. Vegetative Organe der Morpho-Gattung <i>Lindleycladus</i> (incertae sedis) sind ebenfalls erhalten. Das Vorkommen von <i>Lindleycladus</i> ist ein erster Nachweis dieser fossilen Morpho-Gattung in der Südhemisphäre. Anatomische Merkmale dieser Koniferen werden als Anpassungen an ein warmes, saisonal trockenes Klima gedeutet. Im Zusammenhang mit den Koniferenresten werden taphonomische Probleme diskutiert. <br><br> doi:<a href="http://dx.doi.org/10.1002/mmng.20040070109" target="_blank">10.1002/mmng.20040070109</a>
7
Atkinson, Brian A., Dori L. Contreras, Ruth A. Stockey, and Gar W. Rothwell. "Ancient diversity and turnover of cunninghamioid conifers (Cupressaceae): two new genera from the Upper Cretaceous of Hokkaido, Japan." Botany 99, no. 8 (2021): 457–73. http://dx.doi.org/10.1139/cjb-2021-0005.
Texto completo da fonteResumo:
Conifers of the taxodiaceous grade of Cupressaceae were more diverse and widespread during the Mesozoic than they are today. The earliest diverging subfamily, Cunninghamioideae, only includes a single extant genus, but has at least 10 fossil genera. Here, two additional cunninghamioid genera are characterized on the basis of permineralized seed cones from the Upper Cretaceous of Hokkaido, Japan. These conifers display seed cone characters typical of cunninghamioids; however, they have a mosaic of characters that are not seen in any reported conifer of Cupressaceae. They are, therefore, designated as two new extinct species: Ohanastrobus hokkaidoensis gen. et sp. nov. and Nishidastrobus japonicum gen. et sp. nov. These newly reported conifers expand the taxonomic and morphological diversity of cunninghamioids. The stratigraphic and paleobiogeographic records of cunninghamioids and other fossil Cupressaceae with foliate seed cones indicate they peak in diversity during the Cretaceous. The living genera Taiwania and Cunninghamia appear during the Albian and Campanian, respectively, and maintain a nearly continuous fossil record through to today, while nearly all other extinct genera of Cupressaceae with foliate cones disappear by the close of the Campanian. As more ancient cunninghamioids are recovered, our understanding of macroevolutionary patterns of this once diverse lineage will be further elucidated.
8
Kvaček, Jiří, and Jakub Sakala. "Late Cretaceous flora of James Ross Island (Antarctica) – preliminary report." Czech Polar Reports 1, no. 2 (2011): 96–103. http://dx.doi.org/10.5817/cpr2011-2-9.
Texto completo da fonteResumo:
Fossil plants from Late Cretaceous strata (Hidden Lake Formation and Santa Marta Formation) of James Ross Basin exposed in the northern part of the James Ross Island are preliminary described. Both formations contain plant mega fossils, petrified wood, and charcoalified mesofossils. Fossil plants from the Hidden Lake Formation are represented by leaf impressions of pteridophytes (Microphyllopteris, Delosorus, Lygodium), conifers (Elatocladus, Brachyphyllum, Pagiophyllum, Araucaria, Podozamites vel Lindleycladus), Bennettitales vel Cycadales (Zamites vel Dioonites sp.) and angiosperms (Cinnamomoides, Dicotylophyllum ssp., Proteophyllum, Juglandi-phyllum vel Dicotylophyllum). Fossil wood can be attributed to the very broadly defined morphogenus Antarctoxylon Poole & Cantrill.
9
Condamine, Fabien L., Daniele Silvestro, Eva B. Koppelhus, and Alexandre Antonelli. "The rise of angiosperms pushed conifers to decline during global cooling." Proceedings of the National Academy of Sciences 117, no. 46 (2020): 28867–75. http://dx.doi.org/10.1073/pnas.2005571117.
Texto completo da fonteResumo:
Competition among species and entire clades can impact species diversification and extinction, which can shape macroevolutionary patterns. The fossil record shows successive biotic turnovers such that a dominant group is replaced by another. One striking example involves the decline of gymnosperms and the rapid diversification and ecological dominance of angiosperms in the Cretaceous. It is generally believed that angiosperms outcompeted gymnosperms, but the macroevolutionary processes and alternative drivers explaining this pattern remain elusive. Using extant time trees and vetted fossil occurrences for conifers, we tested the hypotheses that clade competition or climate change led to the decline of conifers at the expense of angiosperms. Here, we find that both fossil and molecular data show high congruence in revealing 1) low diversification rates, punctuated by speciation pulses, during warming events throughout the Phanerozoic and 2) that conifer extinction increased significantly in the Mid-Cretaceous (100 to 110 Ma) and remained high ever since. Their extinction rates are best explained by the rise of angiosperms, rejecting alternative models based on either climate change or time alone. Our results support the hypothesis of an active clade replacement, implying that direct competition with angiosperms increased the extinction of conifers by pushing their remaining species diversity and dominance out of the warm tropics. This study illustrates how entire branches on the Tree of Life may actively compete for ecological dominance under changing climates.
10
Taylor, David W., J. Michael Moldowan, and Leo J. Hickey. "Investigation of the terrestrial occurrence and biological source of the petroleum geochemical biomarker oleanane." Paleontological Society Special Publications 6 (1992): 286. http://dx.doi.org/10.1017/s2475262200008467.
Texto completo da fonteResumo:
Oleanane is a triterpane that is commonly found in Late Cretaceous (Campanian) through Cenozoic marine and deltaic rocks and related oils. Based on its affinity to the β-Amyrin group of natural products and its abundance in Tertiary deltaic sediments and oils, such as in the Niger Delta, oleanane is thought to be a geochemical fossil of terrestrial flowering plants. The β-Amyrin group forms the basis of many angiosperm triterpenoids and triterpenoid saponins. These compounds appear in moderately advanced flowering plant lineages and are often used as a defense against herbivores. This group of compounds has not been reported from any other seed plant group, including conifers.We examined a suite of middle to early Cretaceous terrestrial sediments and plant fossils for the presence of oleanane. The existence of oleanane was documented by Gas Chromatography - Mass Spectrometry (GC-MS) and confirmed with Metastable Reaction Monitoring (MRM) GC-MS.Oleanane was identified from fossil bennettitaleans, an extinct group of seed plants. Cycadeoidea paynei and C. superba are permineralized fossil stems and are from the Early Cretaceous Inyan Kara Group of the Black Hills, SD. Oleanane was also found in carbonaceous compressed leaf fossils of Dioonites from the Barremian - early Aptian (Zone I) of the Potomac Group from Richmond, VA. This increases the number of seed plant groups known to have oleanane, and is of additional interest as the bennettitaleans are thought to be closely related to angiosperms.Oleanane was not found in contemporaneous fossil conifers. Our sample consisted of fossil conifer wood collected from the Campanian Magothy Beds of Martha's Vineyard, MA; the Cenomanian Raritan Formation of Sayreville, NJ; and the Barremian - early Aptian Patuxent Formation of Greenbelt, MD.Confirmed reports of oleanane have been from Late Cretaceous and younger marine sediments. We now report oleanane from Early Cretaceous terrestrial strata of the Inyan Kara Group. In addition we systematically sampled the sequence of Cretaceous terrestrial sediments of the coastal plain of the eastern U.S.A, and found oleanane in the Barremian - early Aptian (Zone I) Potomac Group. Preliminary data indicate variation in the occurrence of oleanane in contemporaneous Early Cretaceous sites from the Potomac Group. The localities accumulated in different depositional environments and the occurrence may be controlled by lithofacies.
Teses / dissertações sobre o assunto "Coniferâs, Fossil"
1
Ewin, Timothy Alfred. "Identification of conifer families using SEM analysis of fossil and extant conifer leaf cuticles." Thesis, University of Manchester, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.493777.
Texto completo da fonteResumo:
The cuticles of 58 extant conifer species are examined using scanning electron microscopy (SEM) and described in detail for the first time. The chosen species include representatives of all extant conifer families and also coincide with the species used in various recent genetic conifer phylogenies. A detailed phylogeny of the Coniferales has been compiled by the amalgamation of published genetic phylogenies. Sixty nine cuticle characteristics are identified and scored a numerical system, similar to numerical analyses by Alvin et al (1982). The character scores are plotted onto the Conifer phylogeny using the computer program MacClade 3.04 which is also used to display visually the distribution of each cuticle character. This allows the distribution of the characters to be examined easily, over the entire conifer phylogeny, and thus for groups of characters shared between species from the same family to be recognised. The cuticle characters of 38 other extant conifer species are taken from published accounts, scored and plotted onto the phylogeny by the same method. Lists of diagnostic cuticle characters for each conifer family are presented. The six modern conifer families are differentiated using leaf and cuticle characteristics alone. The cuticle characters indicative of the extant conifer families have been identified in the cuticles of several Mesozoic conifers previously assigned to modern conifer families on the basis of reproductive organs. Most of the descriptions of these fossil species are taken from published literature, with a further 18 fossil species examined by SEM for the first time. It is demonstrated that fossil cuticles display the same cuticle and leaf characteristics as the extant forms and can be assigned to modern families on this basis. Thus the assignment of some fossil species to modern genera or supra generic groups can be questioned using evidence from cuticles. Well-presented conifer cuticles of previously unknown affinity can be confidently or tentatively placed within modern families.
2
Barral, Cuesta Abel. "The carbon isotope composition of the fossil conifer Frenelopsis as a proxy for reconstructing Cretaceous atmospheric CO2." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSE1148.
Texto completo da fonteResumo:
Le Crétacé a été une période d'instabilité climatique et du cycle du carbone, dont le CO2 atmosphérique a été désigné comme le driver majeur. Cependant, les reconstitutions du CO2 atmosphérique ne reflètent ni les dynamiques climatiques ni les grands évènements de perturbation du cycle du carbone décrits pour cette période. J'ai utilisé la composition isotopique de carbone de la plante fossile Frenelopsis (d13Cleaf) comme un nouvel proxy pour reconstituer le CO2 atmosphérique du Crétacé en termes de composition isotopique de carbone (d13CCO2) et de concentration (pCO2). La première courbe de d13CCO2 pour toute la durée du Crétacé a été construite à partir du d13C des carbonates marins. Sa comparaison avec des estimations de d13CCO2 à partir du d13Cleaf a révélé que les modèles développés jusqu'à maintenant ont une tendance à exagérer les valeurs de d13CCO2. Des estimations du fractionnement isotopique du carbone issu par des plantes (13Cleaf) obtenues à partir des nouvelles données d e d13Cleaf et d13CCO2 ont permis de reconstituer l'évolution à grande échelle de la pCO2. Ces résultats indiquent que le CO2 a probablement été une conséquence à long terme du changement climatique durant le Crétacé. Des cycles de d13CCO2 de ~1.2, ~2.1, ~5.4 et ~10.2 Ma ont été détectés, synchrones à ceux du niveau de la mer et à la cyclicité des paramètres de l'orbite terrestre décrits pour le Mésozoïque. Mes résultats fournissent une nouvelle perspective du système climatique et du cycle du carbone du Crétacé, dominés principalement par les paramètres orbitaux de la Terre et secondairement par des évènements catastrophiques de libération de CO2 d'origine volcanique dans l'atmosphère<br>The Cretaceous was a period characterized by strongly marked climate change and major carbon cycle instability. Atmospheric CO2 has repeatedly been pointed out as a major agent involved in these changing conditions during the period. However, long-term trends in CO2 described for the Cretaceous are not consistent with those of temperature and the large disturbance events of the carbon cycle described for the period. This raises a double question of whether descriptions of the long-term evolution of atmospheric CO2 made so far are accurate or, if so, atmospheric CO2 was actually a major driver of carbon cycle and climate dynamics as usually stated. In this thesis the close relationship between the carbon isotope composition of plants and atmospheric CO2 is used to address this question. Based on its ecological significance, distribution, morphological features and its excellent preservation, the fossil conifer genus Frenelopsis is proposed as a new plant proxy for climate reconstructions during the Cretaceous. The capacity of carbon isotope compositions of Frenelopsis leaves (d13Cleaf) to reconstruct past atmospheric CO2, with regards to both carbon isotope composition (d13CCO2) and concentration (pCO2), is tested based on materials coming from twelve Cretaceous episodes. To provide a framework to test the capacity of d13Cleaf to reconstruct d13CCO2 and allowing for climate estimates from carbon isotope discrimination by plants (?13Cleaf), a new d13CCO2 curve for the Cretaceous based on carbon isotope compositions of marine carbonates has been constructed. Comparison with d13Cleaf-based d13CCO2 estimates reveals that although d13CCO2 and d13Cleaf values follow consistent trends, models developed so far to estimate d13CCO2 from d13Cleaf tend to exaggerate d13CCO2 trends because of assuming a linear relationship between both values. However, given the hyperbolic relationship between ?13Cleaf and pCO2, by considering an independently-estimated correction factor for pCO2 for a given episode, d13Cleaf values may be a valuable proxy for d13CCO2 reconstructions. ?13Cleaf estimates obtained from d13CCO2 and d13Cleaf values were used to reconstruct the long-term evolution of pCO2. The magnitude of estimated pCO2 values is in accordance with that of the most recent and relevant model- and proxy-based pCO2 reconstructions. However, these new results evidence long-term drawdowns of pCO2 for Cretaceous time intervals in which temperature maxima have been described
3
Lu, Yueming. "Détermination de la signature moléculaire des conifères fossiles par la maturation artificielle de leurs homologues actuels : implications paléobotaniques et paléoenvironnementales." Thesis, Université de Lorraine, 2014. http://www.theses.fr/2014LORR0353/document.
Texto completo da fonteResumo:
De nombreuses biomolécules qui constituent les plantes vasculaires ne sont synthétisées que par certains taxons de plantes et ont donc une spécificité chimiotaxonomique. Certaines d'entre elles, tels que les bioterpénoïdes, sont particulièrement résistantes et sont préservées dans les sédiments où elles se transforment en géoterpénoïdes lors de la diagenèse. Ces géoterpénoïdes conservent, partiellement ou totalement, leur spécificité initiale (spécifité paléochimiotaxonomique). Cependant, nos connaissances actuelles en paléochimiotaxonomie botanique, qui permettent d'associer ces biomarqueurs moléculaires à des taxons végétaux, restent encore lacunaires. L'objectif de cette étude est de déterminer la signature moléculaire des familles de conifères fossiles. 68 représentants appartenant aux 7 familles actuelles de conifères ont été artificiellement maturés par pyrolyse en milieu confiné afin de reproduire en laboratoire la transformation des bioterpénoïdes en géopterpénoïdes. Les résultats montrent que les Pinaceae, les Araucariaceae, les Cupressaceae, les Sciadopityaceae, les Podocarpaceae, les Taxodiaceae et les Taxaceae "fossilisés" peuvent se distinguer par la nature et la proportion relative de ces terpénoïdes. De plus, la comparaison des signatures moléculaires ont permis de réaliser des regroupements intergénériques pour chaque famille. Ces regroupements sont comparables avec ceux de la classification phylogénétique. À terme, ces résultats pourront être utilisés dans le cadre d’études paléobotaniques, paléoenvironnementales, environnementales et archéologiques<br>Many biomolecules that constitute terrestrial vascular plants are only synthesized by a restricted number of plant taxa and have thus a chemotaxonomic specificity. Some of these biomolecules, like the terpenoids, are particularly resistant and can be preserved within sediments where they are transformed into geomolecules during diagenesis. Geoterpenoids keep, partially or totally, their initial specificity (palaeochemotaxonomic specificity). However, our current knowledge in botanical palaeochemotaxonomy, allowing to link these plant biomarkers to plant taxa, remains incomplete. The aim of this study is to determine the molecular signature of fossil conifers. In this objective, 68 species belonging to the 7 extant conifer families were subjected to artificial maturation by confined pyrolysis. This process converts the bioterpenoids included within the plant material into geoterpenoids. The results show that the "fossilized" Pinaceae, Araucariaceae, Cupressaceae, Sciadopityaceae, Podocarpaceae, Taxodiaceae and Taxaceae can distinguished from each other by the nature and the relative proportion of these geoterpenoids. The comparison of these molecular signatures allows to achieve intergeneric groups for each family. These groups are comparable to those of the phylogenetic classification. In the future, these results could be used for palaeobotanical, palaeoenvironmental, environmental and archaeological assessments
4
Brown, MJM. "Old plants, new tricks : machine learning and the conifer fossil record." Thesis, 2022. https://eprints.utas.edu.au/47489/1/Brown_whole_thesis.pdf.
Texto completo da fonteResumo:
The palaeobotanical record contains a wealth of information on the evolution and ecology of species, as well as the palaeoenvironment. However, accessing and analysing this information can be challenging. It is not possible to study the ecology of fossils directly, but there are two main inferential approaches to palaeoecology: nearest living relative (NLR) techniques, and physiognomic methods.
In NLR techniques, the taxonomic identity of the fossil is key – once the nearest living relatives of a fossil have been identified, we can study the ecology of living species in order to make inferences about the fossil species. However, there are instances where the nearest living relatives of co-occurring fossils are climatically incompatible, which suggests that some extant taxa inhabit different climates to their fossilised relatives. To date, no study has quantitatively analysed this phenomenon in fossils older than the Quaternary (the last 2.6 million years), possibly because of a lack of suitable methodologies.
Alternatively, physiognomic methods seek to extract environmental signal that is encoded in the fossil morphology. This approach has been widely used for macroscopic leaf traits, but comparatively less for epidermal characters (in particular, the shape and arrangement of epidermal cells). The epidermis is the interface between the plant and its environment and is responsible for many functions, including gas exchange and mediation of transpiration (via stomata), so there is good reason to believe that there will be links between epidermal traits and environment. However, the calibration of epidermal physiognomic proxies has been hampered by the non-feasibility of undertaking large multivariate studies where each character is extremely time-consuming and laborious to measure, as well as the complex relationships between genetic and plastic variation.
In this dissertation, I explore how we can use novel computational techniques (including machine learning) to glean new insights from the fossil record, with a focus on southern conifers (Podocarpaceae, Araucariaceae, Callitroideae). I present two new computational methods (with accompanying R packages) and their palaeoecological applications.
In the first chapter, I provide an overview of some of the analytical challenges in palaeoecology and why machine learning techniques are well-suited to solve these problems. I also provide a short review of existing machine learning approaches in palaeoecology.
In the second chapter, I present ‘hyperoverlap’, an R package that uses a novel application of a machine learning classifier to evaluate multi-dimensional overlap between point clouds (e.g. occurrence records in climate space). This chapter is published.
In the third chapter, I use ‘hyperoverlap’ to quantitatively examine the fossil record of southern conifers and to identify no-analogue associations (those pairs of fossils for which the nearest living relatives inhabit disparate climatic conditions). By quantitatively analysing the climatic overlap in fossil communities, I found that there is significant lability in the thermal niches of southern conifers, but extreme stability in the precipitation niche, implying that future changes to rainfall regime may pose more of a threat to southern conifers than thermal shifts. This chapter is under review, after revision.
In the fourth chapter, I present ‘epidermalmorph’, an R package that automates the extraction of leaf epidermal traits from images. As well as trait measurement, this package includes tools for pre-processing, estimations of trait reliability (for any study system) and optimising sampling effort.
In the fifth chapter, I use ‘epidermalmorph’ to assess the degree of climatic adaptation in the epidermal cells of Podocarpaceae. I found some evidence for adaptive significance of stomatal index and cell wall undulation, but there were no viable proxies for either tree height or climatic conditions, suggesting that the functional variability in Podocarpaceae leaves is more likely to be plastic, rather than hard-coded.
In the final chapter, I summarise this thesis, discuss the challenges and limitations to applying sophisticated computational techniques to the palaeobotanical record and suggest potential avenues for future research.
Livros sobre o assunto "Coniferâs, Fossil"
1
Dijkstra, S. J. Gymnospermae (Gingophyta et Coniferae). Backhuys Publishers, 1999.
Encontre o texto completo da fonte
2
J, Enright Neal, and Hill Robert S, eds. Ecology of the southern conifers. Smithsonian Institution Press, 1995.
Encontre o texto completo da fonte
3
Srinivasan, Vijayalakshmi. Taxodiaceous conifers from the Upper Cretaceous of Sweden. Royal Danish Academy of Sciences and Letters, 1989.
Encontre o texto completo da fonte
4
Kunzmann, Lutz. Koniferen der Oberkreide und ihre Relikte im Tertiär Europas: Ein Beitrag zur kenntnis ausgestorbener Taxodiaceae und Geinitziaceae fam. nov. Staatliches Museums für Mineralogie und Geologie zu Dresden, 1999.
Encontre o texto completo da fonte
5
The Wollemi pine: The incredible discovery of a living fossil from the age of the dinosaurs. Text Publishing, 2000.
Encontre o texto completo da fonte
6
The Wollemi pine: The incredible discovery of a living fossil from the age of the dinosaurs. Text Publishing, 2005.
Encontre o texto completo da fonteCapítulos de livros sobre o assunto "Coniferâs, Fossil"
1
Górriz-Mifsud, Elena, Aitor Ameztegui, Jose Ramón González, and Antoni Trasobares. "Climate-Smart Forestry Case Study: Spain." In Forest Bioeconomy and Climate Change. Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-030-99206-4_13.
Texto completo da fonteResumo:
AbstractIn Spain, 55% of land area is covered by forests and other woodlands. Broadleaves occupy a predominant position (56%), followed by conifers (37%) and mixed stands (7%). Forest are distributed among the Atlantic (north-western Iberian rim), Mediterranean (rest of the peninsula including the Balearic Islands) and Macaronesian (Canary Islands) climate zones. Spanish woodlands provide a multiplicity of provisioning ecosystem services, such as, wood, cork, pine nuts, mushrooms and truffles. In terms of habitat services, biodiversity is highly relevant. Cultural services are mainly recreational and tourism, the latter being a crucial economic sector in Spain (including rural and ecotourism). Regulatory services, such as erosion control, water availability, flood and wildfire risk reduction, are of such great importance that related forest zoning and consequent legislation were established already in the eighteenth century. Climate change in Southern Europe is forecast to involve an increase in temperature, reduction in precipitation and increase in aridity. As a result, the risks for natural disturbances are expected to increase. Of these, forest fires usually have the greatest impact on ecosystems in Spain. In 2010–2019, the average annual forest surface area affected by fire was 95,065 ha. The combination of extreme climatic conditions (drought, wind) and the large proportion of unmanaged forests presents a big challenge for the future. Erosion is another relevant risk. In the case of fire, mitigation strategies should combine modification of the land use at the landscape level, in order to generate mosaics that will create barriers to the spread of large fires, along with stand-level prevention measures to either slow the spread of surface fires or, more importantly, impede the possibility of fire crowning or disrupt its spread. Similarly, forest management can play a major role in mitigating the impact of drought on a forest. According to the land use, land-use change and forestry (LULUCF) accounting, Spanish forests absorbed 11% of the total greenhouse gas emissions in 2019. Investments in climate-smart forestry provide opportunities for using all the different parts of the Spanish forest-based sector for climate mitigation––forest sinks, the substitution of wood raw materials and products for fossil materials, and the storage of carbon in wood products. Moreover, this approach simultaneously helps to advance the adaptation of the forest to changing climate and to build forest resilience.
2
TAYLOR, T. "Conifers." In Biology and Evolution of Fossil Plants. Elsevier, 2009. http://dx.doi.org/10.1016/b978-0-12-373972-8.00021-8.
Texto completo da fonte
3
Love*, Renee L., Lindsay MacKenzie*, and Ian Spendlove*. "Uncovering a Miocene forest in ancient Lake Clarkia and beyond." In Proterozoic Nuna to Pleistocene Megafloods: Sharing Geology of the Inland Northwest. Geological Society of America, 2024. http://dx.doi.org/10.1130/2024.0069(06).
Texto completo da fonteResumo:
ABSTRACT The middle Miocene Clarkia Fossil Beds of northern Idaho, USA, is a world-renowned exceptional fossil deposit (Fossil-Lagerstätte). These ancient lake deposits contain fossils showing exceptional preservation of original plant material, insects, and fish, including organelles and possible ancient DNA, and their stable isotope signatures. Yang et al. (1995) determined the upper age of the lake deposits to be 15.78 ± 0.039 Ma during peak outflows of the Priest Rapids Member of the Wanapum Basalt of the Columbia River Basalt Group, part of Earth’s youngest large igneous province of continental flood basalts. The deposits capture a time in Earth’s history that represents our most recent major thermal optima, the Miocene Climatic Optimum, before the general decline in temperatures to the modern day. Nearby fossil sites, including the Oviatt Creek Fossil Beds and the Juliaetta Fossil Beds, record the persistence of the climatic optimum and subsequent cooling. Conifers include Metasequoia (dawn redwood), Taxodium (bald cypress), Amentotaxus (Chinese yew), and Cunninghamia (Chinese fir). Angiosperm dicotyledon species also represent a much warmer climate than present day, including Cercidiphyllum (katsura), Zenia (Chinese legume), Zelkova (elm family), Magnolia (magnolia), Persea (avocado/bay family), Zizyphoides (buckthorn family), and Smilax (greenbriar). Estimates of the mean annual temperature from these fossil leaves range from 12° to 13 °C (53° to 55 °F). Mean annual precipitation values range from 200 to 216 cm/year with much higher humidity compared to today. Modern mean annual temperatures in northern Idaho are ~7 °C (47 °F), much cooler than Miocene temperatures. Today’s mean annual precipitation is estimated at ~80 cm/year. After the Miocene, many plant species representing mixed mesophytic broad-leaved forests started to disappear from the fossil record in North America and were thought to be extinct, only to be rediscovered in East Asia in more recent times (Cercidiphyllum, Cunninghamia, Metasequoia). This field trip will explore the Clarkia Fossil Beds and nearby fossil sites to examine the geology associated with the ancient lake and its fossils.
4
Savill, Peter, Julian Evans, Daniel Auclair, and Jan Falck. "Short-rotation crops." In Plantation Silviculture in Europe. Oxford University PressOxford, 1997. http://dx.doi.org/10.1093/oso/9780198549093.003.0015.
Texto completo da fonteResumo:
Abstract In temperate regions, short-rotation crops may be considered as those grown on rotations of less than about 30 years. Many traditional, broadleaved coppice crops fulfil this definition but it also includes some short-rotation plantations grown for specialized products, notably Populus spp. and Eucalyptus spp. and some conifers grown directly for pulp with no intermediate thinnings. With the present European trend towards diversified land uses, and in particular the ‘set-aside’ policy, increasing areas of former agricultural land will become available for non-food crops. Rather than having this land left fallow, one interesting possibility for farmers is short-rotation forestry. In addition, since the 1970s’ energy crisis and with increasing environmental concern about energy production—whether from carbon dioxide-producing fossil fuels or from nuclear plants—several alternative energy sources are being considered, including short-rotation forest biomass (Christersson 1994).
5
Morey, Elsie Darrah. "Carl Rudolf Florin (1894–1965): A pioneer in fossil-conifer studies." In Historical Perspective of Early Twentieth Century Carboniferous Paleobotany in North America. Geological Society of America, 1995. http://dx.doi.org/10.1130/mem185-p119.
Texto completo da fonte
6
Ornduff, Robert. "The Sequoia Sempervirens (Coast Redwood) Forest of the Pacific Coast, USA." In Coastally Restricted Forests. Oxford University PressNew York, NY, 1997. http://dx.doi.org/10.1093/oso/9780195075670.003.0015.
Texto completo da fonteResumo:
Abstract Since its discovery in the late 18th century, scientists and lay persons alike have been impressed by the magnificence of the stately Sequoia sempervirens (coast redwood) and the dense forests it forms. Yet this conifer is one of the world’s most restricted tree species, occurring only along a very narrow portion of the Pacific coast of California and Oregon. Within this narrow range, however, S. sempervirens exerts a powerful ecological influence in its ecosystem. This chapter describes the morphological features of S. sempervirens, its geographical distribution and the factors that limit this distribution, other organisms that occur with it, ecological dynamics of its forests, its fossil record, its economic values, and its conservation status. It also poses some questions concerning S. sempervirens ecology that remain to be answered.
7
Paracer, Surindar, and Vernon Ahmadjian. "Fungal Associations Of Protozoa And Animals." In Symbiosis. Oxford University PressNew York, NY, 2000. http://dx.doi.org/10.1093/oso/9780195118063.003.0007.
Texto completo da fonteResumo:
Abstract Morn than 1 million species of fungi are estimated to exist, but only about 69,000 species have been described. Most of the undescribed fungi occur in tropical and subtropical regions of the world (Hawksworth and Rossman, 1997). Some fungi are large, like mushrooms, but most of them are microscopic. Armillaria bulbosa, a fungal parasite of the roots of conifers and hardwoods, may be one of the largest and oldest living organisms. One individual strain of this fungus occupies more than 30 acres of Michigan forest, weighs more than 11.0 tons, and is estimated to be 1500 years old (M.L. Smith et al., 1992). Fungi grow practically everywhere and produce large numbers of asexual spores that float in the air, are buried in soil and water, and cling to plants and animals. Under favorable conditions, the spores germinate and produce colonies. About two-thirds of all fungal species live in symbiotic associations with a wide variety of organisms. The major groups of filamentous fungi are ancient in origin, with a fossil record from the Precambrian and early Paleozoic (Sherwood-Pike, 1991).
8
Dolezych, M., L. Reinhardt, J. Kus, and V. Annacker. "Taxonomy of Cretaceous–Paleogene coniferous woods and their distribution in fossil Lagerstätten of the high latitudes." In Circum-Arctic Structural Events: Tectonic Evolution of the Arctic Margins and Trans-Arctic Links with Adjacent Orogens. Geological Society of America, 2019. http://dx.doi.org/10.1130/2018.2541(02).
Texto completo da fonteTrabalhos de conferências sobre o assunto "Coniferâs, Fossil"
1
Brown, Alexander L., and Richard A. Jepsen. "Forest Thinning Residues as a Potential Fuel Source." In ASME 2009 International Mechanical Engineering Congress and Exposition. ASMEDC, 2009. http://dx.doi.org/10.1115/imece2009-11679.
Texto completo da fonteResumo:
Northern New Mexico forests are characterized predominantly by small (i.e. around 10 cm diameter), densely populated conifers. Land managers, both private and government, often thin the forests to reduce the risks from wildland fire. Thinned residues typically amount to approximately 20 to 50 tons per acre. With no obvious market use for these small thinning residues, they are presently either discarded on the ground, or burnt as waste. Through a small business assistance initiative, Sandia National Laboratories is helping to identify and promote process improvements. Several productive uses of the residues have been evaluated, and are presented. The concept of a mobile pyrolysis unit is presently being examined in more detail for several pragmatic reasons. It could remove a significant fraction of the mass as a dense liquid that could be shipped to a refinery for conversion to a fossil fuel additive or substitute. Also, it is a process that is sufficiently well self contained that it could be reasonably sized for a mobile system. Present issues with the concept are addressed, including yield, benefit, and cost.
2
Leng, Qin, Jiaqi Liang, Daianne Höfig, et al. "Assessment of natural variations of key fossil parameters in conifer species and their impact on the accuracy of the leaf gas exchange model for ancient CO2 reconstruction." In Goldschmidt2021. European Association of Geochemistry, 2021. http://dx.doi.org/10.7185/gold2021.6576.
Texto completo da fonte