Response Of Late Carboniferous And Early Permian Plant Communities To Climate Change

Late Carboniferous and Early Permian strata record the transition from a cold interval in Earth history, characterized by the repeated periods of glaciation and deglaciation of the southern pole, to a warm-climate interval. Consequently, this time period is the best available analogue to the Recent in which to study patterns of vegetational response, both to glacial-interglacial oscillation and to the appearance of warm climate. Carboniferous wetland ecosystems were dominated by spore-producing plants and early gymnospermous seed plants. Global climate changes, largely drying,forced vegetational changes, resulting in a change to a seed plant–dominated world, beginning first at high latitudes during the Carboniferous, reaching the tropics near the Permo-Carboniferous boundary. For most of this time plant assemblages were very conservative in their composition. Change in the dominant vegetation was generally a rapid process, which suggests that environmental thresholds were crossed, and involved little mixing of elements from the wet and dry floras

THE EFFECT OF LEAF ORIENTATION TO SUNLIGHT ON STOMATAL PARAMETERS OF QUERCUS RUBRA AROUND THE BELGRADE LAKES, CENTRAL MAINE

ABSTRACT Stomatal frequencies of fossil-plant species are used to estimate past pCO 2 levels based on the physiological functions of living taxa. There is a demonstrable inverse relationship between increasing pCO 2 and stomatal frequency parameters, in which there is a decrease in both stomatal density (SD) and stomatal index (SI). Concentration of CO 2 is not the only factor known to affect SD and SI values, which are a product of leaf development and expansion, as studies have shown a positive correlation between SD and light intensity. The present study tests the hypothesis that SD and SI are not influenced by a leaf's physical orientation relative to the sun during the growing season. Sun leaves of northern red oak, Quercus rubra, were collected from trees around the margins of six lakes of the Belgrade Lakes Region, central Maine, United States, in 2007. Lakes in NE-SW, NW-SE, and E-W orientations allowed for sampling of trees exposed to varying light intensities throughout the growing-season day. The SD and SI of each tree were calculated, and statistical comparisons were made between populations exposed to predominant morning or afternoon light intensities for each lake and between populations on lakes of differing orientations. There is no statistically significant difference in either SD or SI between populations growing under different orientations to growing-season sunlight. These data indicate that exposure to various sunlight regimes on opposite sides of a lake does not play a role in the stomatal response as reflected in SD and SI of plants during a single growing season

Changes in shell durability of common marine taxa through the Phanerozoic: evidence for biological rather than taphonomic drivers.

Abstract.-Phanerozoic trends in shell and life habit traits linked to postmortem durability were evaluated for the most common fossil brachiopod, gastropod, and bivalve genera in order to test for changes in taphonomic bias. Using the Paleobiology Database, we tabulated occurrence frequencies of genera for 48 intervals of ,11 Myr duration. The most frequently occurring genera, cumulatively representing 40% of occurrences in each time bin, were scored for intrinsic durability on the basis of shell size, reinforcement (ribs, folds, and spines), life habit, and mineralogy. Shell durability is positively correlated with the number of genera in a time bin, but durability traits exhibit different temporal patterns across higher taxa, with notable offsets in the timing of changes in these traits. We find no evidence for temporal decreases in durability that would indicate taphonomic bias at the Phanerozoic scale among commonly occurring genera. Also, all three groups show a remarkable stability in mean shell size through the Phanerozoic, an unlikely pattern if strong sizefiltering taphonomic megabiases were affecting the fossil record of shelly faunas. Moreover, small shell sizes are attained in the early Paleozoic in brachiopods and in the latest Paleozoic in gastropods but are steady in bivalves; unreinforced shells are common to all groups across the entire Phanerozoic; organophosphatic and aragonitic shells dominate only the oldest and youngest time bins; and microstructures having high organic content are most common in the oldest time bins. In most cases, the timing of changes in durability-related traits is inconsistent with a late Mesozoic Marine Revolution. The post-Paleozoic increase in mean gastropod reinforcement occurs in the early Triassic, suggesting either an earlier appearance and expansion of durophagous predators or other drivers. Increases in shell durability hypothesized to be the result of increased predation in the late Mesozoic are not evident in the common genera examined here. Infaunal life habit does increase in the late Mesozoic, but it does not become more common than levels already attained during the Paleozoic, and only among bivalves does the elevated late Mesozoic level persist through the Holocene. These temporal patterns suggest control on the occurrence of durability-related traits by individual evolutionary histories rather than taphonomic megabiases. Our findings do not mean taphonomic biases are absent from the fossil record, but rather that their effects apparently have had little net effect on the relative occurrence of shell traits generally thought to confer higher preservation potential over long time scales

STUDIES ON NORTH AMERICAN PECOPTERIDS. III. PECOPTERIS BUTTSII D. WHITE FROM THE EARLY PENNSYLVANIAN OF ALABAMA

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact [email protected]. . ABSTRACT-The form genus Pecopteris Brongniart is rare in Lower Pennsylvanian strata. Those species originally described from North America need to be reinvestigated to determine their relationship to the more extensively described European forms. The occurrence of early Pennsylvanian pecopterids is significant because they represent the early history of this group, which becomes dominant in the Westphalian D. SEPM Society for Sedimentary Geology Pecopteris buttsii D. White was originally established for a lobate pinnuled pecopterid from the Brookwood coal horizon (New River equivalent, Westphalian A), Warrior coalfield, Alabama. The species was invalidly published and a study of the type specimen was initiated to discern its affinity. Attempts at collecting additional specimens from the type area have failed and the formal description is based upon fragments of seven third or possibly fourth order (?) pinnae. Additional specimens of P. buttsii (?) from Tennessee were also examined to discern their relationship with the holotype. Consideration of parameters necessary to erect form taxa is highly complex and many factors must be assessed prior to establishment of a new form. These parameters include the degree of morphological homology between specimens and their reported temporal isolation or continuation. Frequency of occurrence should not be considered as a delimiting character nor should size or preservational configuration

Plant Biodiversity Partitioning in the Late Carboniferous and Early Permian and Its Implications for Ecosystem Assembly

Volume: 56, Supplement IStart Page: 32End Page: 4

Ecological Persistence in the Late Mississippian (Serpukhovian, Namurian A) Megafloral Record of the Upper Silesian Basin, Czech Republic

The Serpukhovian (Namurian A) stratigraphy of the Ostrava Formation, Upper Silesian Coal Basin, Czech Republic, consists of coal-bearing paralic sediments underlain by marine deposits in a cyclothemic nature similar to those in the Pennsylvanian of Euramerica. The thickness of the formation exceeds 3000 m, in which \u3e170 coals are identified in a foreland basin setting. Fifty-five genetic cycles are identified in the present study, using transgressional erosional surfaces as lower and upper boundaries. Terrestrial plant-macrofossil assemblages are preserved within each cycle, mostly associated with coals, and these represent a sampling of the coastal plain vegetation. New high-precision isotope dilution–thermal ionization mass spectrometry U-Pb ages on zircons from tonsteins of two coals provide chronometric constraints for the Serpukhovian. Unweighted Pair Group Method with Arithmetic Mean clustering and Bayesian statistical classification group macrofloral assemblages into four distinct stratigraphic clusters, with assemblages persisting for \u3c18 cycles\u3ebefore compositional change. Cycle duration, based on Ludmila (328.84±0.16 Ma) and Karel (328.01±0.08 Ma) tonsteins, overlaps the short-period (100 kyr) eccentricity cycle at the 95% confidence interval. These dates push the beginning of the Serpukhovian several million years deeper in time. An estimate for the Visean-Serpukhovian boundary is proposed at 330 Ma. Late Mississippian wetland ecosystems persisted for \u3e1.8 million years before regional perturbation, extirpation, or extinction of taxa occurred. Significant changes in the composition of macrofloral clusters occur across major marine intervals. These results accord with other estimates of Carboniferous tropical wetland community persistence. Hence, vegetational persistence was characteristic of peat-accumulating and mineral-substrate wetland ecosystems beginning in the Late Mississippian, when there is evidence for the first appearance of eustatically controlled cyclothems during the buildup of Gondwanan glaciation