PHYSIOLOGICAL FUNCTIONING OF SEASONALLY DRY ADAPTED FLORAS IN RESPONSE TO CHANGES IN LATE PALEOZOIC ATMOSPHERIC COMPOSITION

2018 ◽  
Author(s):  
Jon D. Richey ◽  
◽  
Joseph D. White ◽  
Isabel P. Montañez ◽  
Jonathan P. Wilson ◽  
...  
2019 ◽  
Author(s):  
Jon D. Richey ◽  
◽  
Joseph D. White ◽  
Isabel P. Montañez ◽  
William J. Matthaeus ◽  
...  

2020 ◽  
Author(s):  
Gerilyn Soreghan ◽  
Laurent Beccaletto ◽  
Kathleen Benison ◽  
Sylvie Bourquin ◽  
Natsuko Hamamura ◽  
...  

<p>The climatic, biotic, and tectonic events of the Permian are amongst the most profound in Earth history. Global orogeny leading to Pangaean assembly culminated by middle Permian time, and included multiple orogenic belts in the equatorial Central Pangaean Mountains, from the Variscan-Hercynian system (east) to the Ancestral Rocky Mountains (west). Earth’s penultimate global icehouse peaked in early Permian time, transitioning to full greenhouse conditions by late Permian time, thus archiving the only example of icehouse collapse on a fully vegetated Earth. The Late Paleozoic Icehouse was the longest and most intense glaciation of the Phanerozoic, with hypothesized low-elevation glaciation posited for both eastern and western tropical Pangaea during early Permian time. Reconstructions of atmospheric composition record the lowest CO<sub>2</sub> and highest O<sub>2</sub> levels of the Phanerozoic, with average CO<sub>2</sub> levels comparable to the Quaternary, rapidly warming climate. Fundamental shifts occurred in atmospheric circulation: a global megamonsoon developed and the tropics became anomalously arid with time. Extreme environments are well documented in the form of voluminous dust deposits, acid-saline lakes and groundwaters, extreme continental temperatures and aridity, and major extinctions/extirpations, ultimately culminating at the Permo-Triassic boundary with the largest extinction of Earth history.</p><p>We seek to elucidate paleoclimatic conditions and forcings through the Permian at temporal scales ranging from the millennial to the Milankovitch<span>  </span>and beyond by acquiring continuous core in continental lowlands known to harbor stratigraphically complete records dominated by loess and lacustrine strata. We have identified sites in the western U.S. and Europe as the key sites globally to achieve our objectives, as these represent the western and eastern limits, respectively of the Pangaean tropics. Identified sites harbor arguably the most complete continental Permian sections in the paleoequatorial region, with adjacent paleo-uplands hypothesized to have hosted glaciation. We will also address the nature and character of the modern and fossil microbial biosphere, Mars-analog conditions, and exhumation histories of source regions.</p>


Author(s):  
J.A. Lancashire ◽  
J.L. Brock

Some characteristics of seed quality, establishment rates, performance in mixtures and response to grazing management of 5 new pasture plants with potential in dryland are described. On a dry hill country site in the Wairarapa, the contribution of the sown grasses established in separate plots with clovers under rotational grazing was 'Grasslands Wana' cocksfoot 65%; 'Grasslands Maru' phalaris 23%; 'Grasslands Matua' prairie grass 22%; and 'Grasslands Roa' tall fescue 13% after 2 years. The other main grass species was resident perennial ryegrass which established from buried seed (ca. 240 plants/m*) and had a major impact on the establishment and growth of the sown grasses. On a seasonally dry Manawatu flat land soil 3 grazing managementsviz. set stocked all year (S); rotational all year (R); and combination (Cl (set stocked from lambing to drafting and rotational for the remainder of the year) were applied to mixtures of the new cultivars (except that 'Grasslands Apanui' cocksfoot replaced Wana) with ryegrass and white clover stocked at 20 sheep/ha. After 3 years the contribution of the new cultivars was negligible under S and ryegrass was dominant. The R pastures became cocksfoot dominant and Matua (in winter) and chicory (in summer) contributed more than in the S system. The C system produced the most evenly balanced species contribution with only Roa remaining at (5%. A sub-trial with cocksfoot cultivars demonstrated that Wana maintained better production and tiller density ~ll,000/m2 ) than Apanui (1000/m' ) under set stocking IS). Although some of the new cultivars will require specialised management procedures to fulfil their potential in dryland, the increasing and widespread use of Matua prairie grass in farming suggests that these techniques can be adopted in commercial agriculture provided good technical information is available in a management package when the cultivar is released. Keywords: Dryland, grazing management, mixtures, Matua prairie grass, Wana cocksfoot, Roa tall fescue, Maru phalaris, Chicory


10.3133/pp858 ◽  
1976 ◽  
Author(s):  
Raymond Charles Douglass ◽  
Merlynd Keith Nestell

2020 ◽  
Vol 57 (3) ◽  
pp. 149-176
Author(s):  
Nur Uddin Md Khaled Chowdhury ◽  
Dustin E. Sweet

The greater Taos trough located in north-central New Mexico represents one of numerous late Paleozoic basins that formed during the Ancestral Rocky Mountains deformation event. The late Paleozoic stratigraphy and basin geometry of the eastern portion of the greater Taos trough, also called the Rainsville trough, is little known because the strata are all in the subsurface. Numerous wells drilled through the late Paleozoic strata provide a scope for investigating subsurface stratigraphy and basin-fill architecture of the Rainsville trough. Lithologic data obtained predominantly from petrophysical well logs combined with available biostratigraphic data from the greater Taos trough allows construction of a chronostratigraphic framework of the basin fill. Isopach- and structure-maps indicate that the sediment depocenter was just east of the El Oro-Rincon uplift and a westerly thickening wedge-shaped basin-fill geometry existed during the Pennsylvanian. These relationships imply that the thrust system on the east side of the Precambrian-cored El Oro-Rincon uplift was active during the Pennsylvanian and segmented the greater Taos trough into the eastern Rainsville trough and the western Taos trough. During the Permian, sediment depocenter(s) shifted more southerly and easterly and strata onlap Precambrian basement rocks of the Sierra Grande uplift to the east and Cimarron arch to the north of the Rainsville trough. Permian strata appear to demonstrate minimal influence by faults that were active during the Pennsylvanian and sediment accumulation occurred both in the basinal area as well as on previous positive-relief highlands. A general Permian decrease in eustatic sea level and cessation of local-fault-controlled subsidence indicates that regional subsidence must have affected the region in the early Permian.


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