Gary Upchurch, Ph.D.
Paleobotany & Global Change
Department of Biology
BIO 1320, Modern Biology I (non-majors)
BIO 1421,Modern Biology II (non-majors)
BIO 4411/5411,Morphology of Vascular Plants
BIO 4412/5412, Plant Anatomy
BIO 5110E, Mass Extinction Seminar
BIO 5308/7308, History of Vegetation and Climate
My formal academic training is in Botany with extensive postdoctoral experience in Earth Science. My research is interdisciplinary and draws from Botany, Geology, and Atmospheric Science. I focus on the history of vegetation and climate, and feedbacks between vegetation and the atmosphere. My long-term goal is to develop a comprehensive history of floras and their environment during the rise of angiosperms and the end-Cretaceous mass extinction, and to identify plant-atmosphere feedbacks that helped shape this history.
I believe that paleobotany has much untapped potential for deciphering the causes of past global change. Plants provide forensic evidence for climatic change and mass mortality because they are sensitive indicators of environment. Plants help regulate climate because they strongly affect the fluxes of energy, water vapor, and carbon dioxide between the land surface and the atmosphere. Plants serve as both environmental indicators and regulators of environmental change. This means that paleobotany can provide important data for climatic reconstruction and important input parameters for Earth System Models.
My empirical studies focus on fossil angiosperm leaves, and in particular leaf megafossils and dispersed leaf cuticles. Leaf megafossils provide a large suite of characters for systematics, yet another suite of characters for environmental reconstruction. Dispersed plant cuticles are the most abundant component of the plant fossil record next to pollen and spores, which means that dispersed cuticles can provide the high sampling intensity needed for studies of paleoecology and floral turnover. Dispersed cuticles form an important complement to palynomorphs because they provide direct evidence on leaf physiognomy and atmospheric CO2 and have different taphonomic histories and sampling biases.
Current and Future Research Projects
The Cretaceous-Tertiary (K-T) boundary serves as the archetypal example of extinction by a bolide impact. Paleobotany provides important forensic evidence for mass mortality associated with impact, rapid extinction of taxa at the K-T boundary, and possible long-term changes in temperature, precipitation, and CO2. Poorly understood are the exact pattern of long-term environmental change and its link to floral turnover, and the three-dimensional response of the climate system to a bolide impact.
A major long-term goal is to elucidate the pattern of long-term floral and environmental change across the K-T boundary in megathermal assemblages from the southern Western Interior and adjacent regions, building on earlier work with Jack Wolfe, Robert Tschudy, and others. This work will integrate the record of leaf megafossils, dispersed cuticles, and palynomorphs with environmental information derived from foliar physiognomy, stomatal indices, and stable isotopes.
A second long-term goal is to model climatic change associated with an end-Cretaceous bolide impact, building on earlier work with Bette Otto-Bliesner and Chris Scotese. The objective is to predict geographic variation in environmental change at the K-T boundary and to use this variation to evaluate patterns of extinction in the marine and terrestrial realms.
Vegetation-atmosphere interactions during the Cretaceous and Cen
Climate strongly influences plant physiognomy and distribution, while plants influence climate through their effects on land-surface physics and the carbon cycle. Modeling studies of Cretaceous and Cenozoic climate indicate that feedbacks between high-latitude forests, the atmosphere, and oceans helped maintain warm polar climates of the geologic past. They also indicate that the shift to grassland and tundra vegetation during the Late Cenozoic amplified cooling and drying trends. Not well understood are mechanistic links between key biological and environmental events, especially in light of new data that contradict earlier ideas on the timing of mountain uplift and levels of atmospheric CO2 during the Cenozoic.
Chris Scotese, Arne Micheels, Jack Wolfe, and I are beginning a project on global paleogeography and vegetation for the Late Miocene (Tortonian) and the feedbacks between mountain uplift, vegetation, and Late Cenozoic cooling and drying. Previous climate modeling studies of the Late Cenozoic, while demonstrating important linkages between uplift, cooling, and drying, could not address timing of key events because they used unrealistic paleogeography. Our global-scale study will produce realistic data sets for modeling the effects of climatic uplift and vegetation change and is unique in its use of paleobotany as a major source of data on paleoelevation, sea ice, and glacial ice.
Angiosperm diversification? The Cretaceous rise of angiosperms was a major event in the history of terrestrial ecosystems. Angiosperm families and orders appeared rapidly during the Cretaceous and caused major changes in species diversity. Changes in ecological dominance also occurred, but their extent and timing are debated. The systematics of Cretaceous angiosperm leaves and their stratigraphic record appear to be consistent with published molecular phylogenies based on multiple genes. However, revision of previous systematic work on fossil angiosperm leaves is needed to evaluate older identifications and document biogeographic history and the minimum age of clades.
I am currently reviewing the Cretaceous and Early Cenozoic leaf record from North America for the four orders of primitive eudicots? Ranunculales, Proteales, Trochodendrales, and Buxales. My preliminary results confirm earlier evidence for the rapid appearance of these four orders during the mid-Cretaceous, and support molecular evidence for a close relationship between Platanaceae (sycamores) and Proteaceae. Another interesting finding is that herbaceous representatives of these orders are present as low-abundance elements in leaf floras preserved in volcanic ash. Geographic and stratigraphic patterns of diversity correlate well with climate.
My students, collaborators, and I are testing competing hypotheses about the role of angiosperms in regional vegetation during the Cretaceous with the analysis of leaf litter and in situ trees. Our results indicate that Late Cretaceous angiosperms were a major component of biomass in megathermal vegetation and comprised trees up to 20 m or more in height. The angiosperm rise to dominance was directly influenced by climate and showed a strong equator to pole gradient.
Dispersed plant cuticles as environmental indicators Plant cuticle-the decay-resistant outer layer of leaves and young stems is the most abundant component of the plant fossil record next to pollen and spores. Plant cuticle has many features diagnostic of taxonomy, yet others diagnostic of climate and atmospheric chemistry. Analysis of plant cuticle has focused on megafossils, but a more palynological approach based on bulk samples shows good potential for paleoenvironmental reconstruction.
Two in-progress studies are exploring new uses of dispersed cuticle in environmental analysis. The first is an analysis of stable carbon isotopes in modern and fossil plant cuticle, which provide a tool for tracking the global carbon cycle. My results indicate that cuticle and whole tissue show a consistent isotopic offset, which means that cuticle can be used to reconstruct the isotopic composition of whole tissue. My results also indicate that the analysis of bulk organic carbon is potentially problematic, because bulk carbon is a mixture of isotopically distinct compounds whose ratios can vary with decay.
The second in-progress study is the use of plant cuticle in the reconstruction of vegetation physiognomy. Thickness of plant cuticle shows a significant correlation with evergreen and deciduous growth habit, which should allow determination of temperature trends and the mapping of freeze lines in the fossil record.
Beerling, D.J., Lomax, B.H., Royer, D.L., Upchurch Jr., G.R., and Kump, L.R., 2002 An atmospheric pCO2 reconstruction across the Cretaceous-Tertiary boundary from leaf megafossils. Proceedings of the National Academy of Sciences USA 99: 7836-7840.
Upchurch, G.R., Jr., 2001. Paleoclimate modelling using fossil plants. In Briggs, D.E.G., and Crowther, P.R., eds., Palaeobiology II. Oxford, Blackwell Science Ltd, p. 487?489.
Beerling, D.J., Lomax, B.H., Upchurch, G.R., Jr., Nichols, D.J., Pillmore, C.L., Handley, L., and Scrimgeour, C.M., 2001. Evidence for recovery of terrestrial ecosystems ahead of marine primary production following a biotic crisis at the Cretaceous-Tertiary boundary. Journal of the Geological Society of London 158: 737-740.
Lomax, B.H., Beerling, D.J., Upchurch, G.R., Jr., and Otto-Bliesner, B.L, 2001. Rapid (10-yr) recovery of terrestrial productivity in a simulation study of the terminal Cretaceous impact event. Earth and Planetary Science Letters 192: 137-144.
Lomax, B.H., Beerling, D.J., Upchurch, G.R., Jr., and Otto-Bliesner, B.L, 2000. Terrestrial ecosystem responses to global environmental change across the Cretaceous-Tertiary boundary. Geophysical Research Letters 27: 2149?2152.
Scott, A.C., Lomax, B.H., Collinson, M.E., Upchurch, G.R., and Beerling, D.J., 2000. Fire across the K/T boundary: initial results from the Sugarite Coal, New Mexico, USA. Palaeogeography, Palaeoclimatology, Palaeoecology 164: 381?395. (Special issue entitled, ?Fire and the Palaeoenvironment?, edited by A.C. Scott, J. Moore, and B. Brayshay).
Knaus, M.J., Upchurch, G.R., Jr., and Gillespie, W.H., 2000. Charbeckia macrophylla gen. et sp. nov. from the Price (Pocono) Formation of southeastern West Virginia. Review of Paleobotany and Palynology 111: 71?92.
Upchurch, G.R., Jr., Otto-Bliesner, B.L, and Scotese, C.R., 1999, Terrestrial vegetation and its effects on climate during the latest Cretaceous. In Barrera, E., and Johnson, C.C., eds., The evolution of Cretaceous ocean/climate systems. Geological Society of America Special Paper 332: 407-435.
Upchurch, G.R., Jr., Otto-Bliesner, B.L, and Scotese, C.R., 1998, Vegetation-atmosphere interactions and their role in global warming during the latest Cretaceous. Philosophical Transactions of the Royal Society of London, Biological Sciences Series, 353: 97-112.
Otto-Bliesner, B.L., and Upchurch, G.R., Jr., 1997, Vegetation-induced warming of high-latitude regions during the Late Cretaceous period. Nature 385: 304-307.
Dunn, K.A., McLean, R.J.C., Upchurch, G.R., Jr., and Folk, R.L., 1997, Enhancement of leaf fossilization potential by bacterial biofilms. Geology 25: 1119-1122.
Upchurch, G.R., Jr., 1995, Dispersed angiosperm cuticles: Their history, preparation, and application to the rise of angiosperms in Cretaceous to Paleocene coals, southern Western Interior of North America. International Journal of Coal Geology 28: 161-227.
Upchurch, G.R., Jr., Crane, P.R., and Drinnan, A.N., 1994, The megaflora from the Quantico locality (Middle to Upper Albian), Lower Cretaceous Potomac Group of Virginia. Virginia Museum of Natural History Memoir 4: 58p.
Upchurch, G.R., Jr., and Wolfe, J.A., 1993, Cretaceous vegetation of the Western Interior and adjacent regions of North America. In Kauffman, E.G., and Caldwell, W.G.E., eds., Cretaceous evolution of the Western Interior Basin. Geological Association of Canada Special Paper 39: 243-281.
Upchurch, G.R., Jr., and Dilcher, D.L.,1990, Cenomanian angiosperm leaf megafossils, Dakota Formation, Rose Creek locality, Jefferson County, southeastern Nebraska. U.S. Geological Survey Bulletin 1915, 55 p. + 31 pls.
Upchurch, G.R., Jr., 1989, Terrestrial environmental changes and extinction patterns at the Cretaceous-Tertiary boundary, North America. In Donovan, S.K., ed., Mass Extinction: Processes and Evidence. London, Belhaven Press, p. 195-216; printed in the United States by Columbia University Press.
Upchurch, G.R., Jr., and Wolfe, J.A., 1987,Mid-Cretaceous to Early Tertiary vegetation and climate: Evidence from fossil leaves and wood. In Friis, E.M., W.G. Chaloner, and P.R. Crane, eds., The origins of angiosperms and their biological consequences. Cambridge, Cambridge University Press, p. 75-105.
Wolfe, J.A., and Upchurch, G.R., Jr., 1987a, Leaf assemblages across the Cretaceous-Tertiary boundary in the Raton Basin, New Mexico and Colorado. Proceedings of the National Academy of Sciences 84: 5096-5100.
Wolfe, J.A., and Upchurch, G.R., Jr., 1987b, North American non-marine climates and vegetation during the Late Cretaceous. Palaeogeography, Palaeoclimatology, Palaeoecology 61: 33-77.
Crane, P.R., and Upchurch, G.R., Jr., 1987, Drewria potomacensis gen. et sp. nov., an Early Cretaceous member of Gnetales from the Potomac Group of Virginia. American Journal of Botany 74: 1723-1738.
Wolfe, J.A., and Upchurch, G.R., Jr., 1986,Vegetation, climatic and floral changes at the Cretaceous-Tertiary boundary. Nature 324: 148-152.
Upchurch, G.R., Jr., 1984, The cuticular anatomy of early angiosperm leaves from the Lower Cretaceous Potomac Group of Virginia and Maryland, Part 1, Zone 1 leaves. American Journal of Botany 71: 192-202.
Upchurch, G.R., Jr., 1984, Cuticular evolution in Early Cretaceous angiosperms from the Potomac Group of Virginia and Maryland. Annals of the Missouri Botanical Garden 71: 518-546.
Upchurch, G.R., Jr., and Doyle, J.A., 1981,Paleoecology of the conifers Frenelopsis and Pseudofrenelopsis (Cheirolepidiaceae) from the Cretaceous Potomac Group of Maryland and Virginia. In Romans, R.C., ed. Geobotany II. NewYork, Plenum Press, p. 167-202.
· Dunn, K.R., 1995, Biofilm Enhancement of Leaf Fossilization Potential. Biology Honors Thesis, Texas State University.
· Cowie, R., 1999, Gas Exchange Characteristics of an Early Cretaceous Conifer, Pseudofrenelopsis varians (Cheirolepidiaceae), and its Inferred Paleoecology. Biology MS Thesis, Texas State University.
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