Research Interests and Publications

My research aims to better understand how plants interact with the atmosphere, and how this relationship has evolved over geological time.

Research Fellowship: The Evolution of C₄ Plants

My Royal Society University Research Fellowship tackles the problems of when, how and why C₄ photosynthesis evolved in plants.

Click here to find out what C₄ photosynthesis is and how it works.

• The origin of C₄ ecosystems occurred abruptly 8 million years ago - the primary cause of this event remains uncertain.
• The C₄ savanna biome now covers 20 million km² of the Earth's land surface, and is home to one fifth of its human population.
• C₄ grasses are exploited extensively in tropical agriculture, counting maize, sugarcane, sorghum and millet among their number.

Today's global distribution of C₄ ecosystms is strongly constrained by climate, especially temperature and rainfall. On geological timescales, low CO₂ atmospheres may also be important for the ecological success of C₄ species, interacting with agents of disturbance like wildfires and large herbivores. Work in my research group investigates questions of how these constraints operate in today's world and how they have evolved through deep time.

Currently, much of this work focuses on the grass Alloteropsis semialata - a species unique in having C₃ and C₄ subtypes. By building a detailed understanding of the genetic origins, physiology and ecology of this species, I hope to make discoveries that will be of broader significance for C₄ grasses in general. This work is carried out in close collaboration with Brad Ripley at Rhodes University in South Africa.

Click here to find out more about Alloteropsis semialata.

The distribution of C₄ grasses in South Africa is thought to result from the interaction of temperature with rainfall. C₄ species prefer hot wet conditions, whilst C₃ grasses dominate in cool climates. How do these climatic preferences arise? And what happens in the large areas of the country where C₃ and C₄ grasses co-dominate.

Research Projects: C₄ Plants

This was published in:

Osborne, C.P., Beerling, D.J. (2006) Nature's green revolution: the remarkable evolutionary rise of C₄ plants. Phil. Trans. Royal Soc. Series B, 361, 173-194. 1.1MB

Beerling, D.J., Osborne, C.P. (2006) The origin of the savannah biome. Global Change Biology, 12, 2023-2031. 300KB

Mechanisms of freezing damage and protection in C₄ plants
Dr Meizhen Liu (Royal Society China Fellowship)

Dr Meizhen Liu is visiting the lab from the Institute of Botany in Beijing. Her research is comparing the induction of freezing tolerance in C₃ and C₄ Mongolian steppe species - is the C₄ pathway always associated with an inability to tolerate freezing, and does this cost differ in grasses and Chenopods?

Frost damage in C₄ grasses
Colin Osborne (Royal Society Research Grant)

My work in this project addresses the question of whether freezing sensitivity is a general characteristic of C₄ grass species, and begins to investigate the causes of frost damage.

The origin and consequences of C₄ photosynthesis in Alloteropsis semialata
Douglas Ibrahim (NERC postgraduate studentship)

Doug is investigating the ancestry and climatic interactions of Alloteropsis semialata using molecular genetics and physiological ecology.
Click here to find out more about his project.

Mechanisms driving the evolution and breakdown of C₄ photosynthesis
Emily Wythe (British Ecological Society research technician)

Emily used controlled growth environments to examine how Alloteropsis semialata responds to CO₂-starvation and low temperatures. This project is now finished.
Click here to find out more about it.

Rising atmospheric CO₂: trigger for the origin of agriculture?
Jennifer Cunniff (University of Sheffield postgraduate studentship, co-supervised by Mike Charles and Glynis Jones)

Jen is examining the responses of wild crop relatives to low atmospheric CO₂ concentrations, using C₄ species to provide a critical test of the hypothesised link between rising CO₂ and the origin of agriculture. Click here to find out more about her project.

Megaherbivores and the superbiome: do consumers control grassland distribution?
Vernon Visser (Dorothy Hodgkin postgraduate studentship; co-supervised by Ian Woodward)

Vernon is developing a new sub-model of herbivore consumption for the Sheffield Dynamic Global Vegetation Model, and using it to investigate the role of large animals in promoting grassland evolution.
Click here to find out more about his project Click here to find out more about his project.

Was declining CO₂ the key to early leaf evolution?

Together with David Beerling and Bill Chaloner (University of London), I developed an explanation for the comparatively late evolution of leaves in early land plants as described on the project page. Our theory was first published in Nature and subsequently tested in a PNAS publication using evidence from the plant fossil record:

Beerling, D.J., Osborne, C.P. & Chaloner, W.G. (2001) Evolution of leaf-form in land plants linked to atmospheric CO₂ decline in the Late Palaeozoic era. Nature, 410, 352-354. 231KB

Kenrick, P. (2001) Turning over a new leaf. Nature, 410, 309-310. 136KB

Hecht, J. (2001) Branching out. New Scientist, 14th March.

Osborne, C.P., Beerling, D.J., Lomax, B.H., Chaloner, W.G. (2004) Biophysical constraints on the origin of leaves inferred from the fossil record. PNAS, 101, 10360-10362. 304KB

Botzer, A. (2005) Turning a new leaf. National Geographic Magazine, December.

Smith, H.J. (2004) Leaf story. Science, 305, 452. 119KB

Gosline, A. (2004) Broad leaves evolved as CO₂ fell. New Scientist, 4th July.

Atmospheric interactions of the extinct polar forest biome

For most of the last 250 million years, the Earth has been in a high CO₂ 'greenhouse' mode, allowing forests to cover the polar regions. The atmospheric interactions allowing this now-extinct polar forest biome to thrive in a high CO₂ atmosphere, warm climate, and extreme daylength regime of the ancient high latitudes has been a long-running theme of collaborative work with David Beerling, Jane Francis and Dana Royer (now Wesleyan University). We have used both experimental and modelling approaches to investigate the costs and benefits of leaf habit for survival of a warm, dark winter, and growth during the continuous light of a polar summer.

For a review of this work written for non-specialist readers see:

Osborne, C.P., Royer, D.L., Beerling, D.J. (2004) Adaptive role of leaf habit in extinct polar forests. International Forestry Review, 6, 181-186. 188KB

Reports of this work in the scientific literature:

Brentnall, S.J., Beerling, D.J., Osborne, C.P., Harland, M., Francis, J.E., Valdes, P.J., Wittig, V.E. (2005) Climatic and ecological determinants of leaf lifespan in polar forests of the high CO₂ Cretaceous ‘greenhouse’ world. Global Change Biology, 11, 2177-2195. 549KB

Royer, D.L., Osborne, C.P., Beerling, D.J. (2005) Contrasting seasonal patterns of carbon gain in evergreen and deciduous trees of ancient polar forests. Paleobiology, 31, 141-150. 540KB

Osborne, C.P., Beerling, D.J. (2003) The penalty of a long hot summer: photosynthetic acclimation to high CO₂ and continuous light in 'living fossil' conifers. Plant Physiology, 133, 803-812. 240KB

Royer, D.L., Osborne, C.P., Beerling, D.J. (2003) Carbon loss by deciduous trees in a CO₂-rich ancient polar environment. Nature, 424, 60-62. 216KB

Click here for news reports of this article:

BBC News - Antarctic Scott's lasting legacy
CBC News - Secret surrounds leaf fall in ancient polar forests

Osborne, C.P. & Beerling, D.J. (2002) A process-based model of conifer structure and function with special emphasis on leaf lifespan. Global Biogeochemical Cycles. 1721KB

Osborne, C.P. & Beerling, D.J. (2002) Sensitivity of tree growth to a high CO₂ environment - consequences for interpreting the characteristics of fossil woods from ancient 'greenhouse' worlds. Palaeogeography, Palaeoclimatology, Palaeoecology, 182, 15-29. (518KB)

Beerling, D.J. & Osborne, C.P. (2002) Physiological ecology of Mesozoic polar forests in a high CO₂ environment. Annals of Botany, 89, 329-339. 201KB

The project pages "The carbon balance of ancient polar forests" and "Understanding the distribution and ecology of ancient polar forests" contain more information relating to this work.

Research Projects: Modern plant-atmosphere interactions

A biomechanical approach for predicting uprooting of urban trees
Emran Mohamad Taram (Universiti Putra Malaysia studentship, co-supervised by Malcolm Press).

Emran is investigating why some urban trees in Kuala Lumpur are more susceptible than others to uprooting during storms, and taking the first steps towards predicting the risk of failure in these species.
Click here to find out more about his project.

Live fast die young: the mechanistic basis of an evolutionary trade-off in plants
Rebecca Atkinson (NERC postgraduate studentship; main supervisor Mark Rees)

Rebecca is using field observations and experiments with monocarpic perennials to investigate why fast-growing species die at a younger age than slow-growers.
Click here to find out more about her project.

How does Mediterranean vegetation respond to anthropogenic global change?

My first work in Sheffield was with Ian Woodward, assessing the sensitivity of Mediterranean ecosystems to present-day changes in climate and atmospheric CO₂. Our modelling studies showed that Mediterranean shrublands are highly sensitive to rising atmospheric CO₂, which provides protection from drought by increasing plant water-use efficiency. Together with greater rainfall, this has led to an increase in vegetation cover over the past decades, observed by satellite.

Osborne, C.P., Mitchell, P.L., Sheehy, J.E. & Woodward, F.I. (2000) Modelling the recent historical impacts of atmospheric CO₂ and climate change on Mediterranean vegetation. Global Change Biology, 6, 445-458. 569KB

Osborne, C.P., Chuine, I., Viner, D. & Woodward, F.I. (2000) Olive phenology as a sensitive indicator of future climatic warming in the Mediterranean. Plant, Cell and Environment, 23, 701-710. 306KB

Osborne, C.P. & Woodward, F.I. (2001) Biological mechanisms underlying recent increases in the NDVI of Mediterranean shrublands. International Journal of Remote Sensing, 22, 1895-1907. 226KB

Woodward, F.I. & Osborne, C.P. (2000) The representation of root processes in models addressing the responses of vegetation to global change. New Phytologist, 147, 223-232. 181KB

For Ian Woodward's staff pages please visit Professor F Ian Woodward

Does the photosynthesis of shaded leaves increase in elevated atmospheric CO₂?

I participated in the Arizona FACE project and Global Change Program of the Smithsonian Institution during my Ph.D. with Steve Long (now University of Illinois). My measurements in a wheat crop and a forest floor herb showed that photosynthesis was stimulated by CO₂ enrichment in shade light, despite significant acclimation.

Osborne, C.P., LaRoche, J., Garcia, R.L., Kimball, B.A., Wall, G.W., Pinter, P.J. Jr., LaMorte, R.L., Hendrey, G.R. & Long, S.P. (1998) Does Leaf Position within a Canopy Affect Acclimation of Photosynthesis to Elevated CO₂? Plant Physiology, 117, 1037-1045. 261KB

Osborne, C.P., Drake, B.G., LaRoche, J., Long, S.P. (1997) Does long-term elevation of CO₂ concentration increase photosynthesis in forest floor vegetation? Indian Strawberry in a Maryland forest. Plant Physiology, 114, 337-344.

Relevant web sites can be found at the following addresses:

• FACE Project
• Smithsonian Institution