A symposium integrating
Background
The CO2 content of the atmosphere has varied over geological time from 1000s of parts per million (ppmV) to less than 200 ppmV. These changes in CO2 concentration have profound effects on terrestrial and marine photosynthesis including increasing the concentration of secondary toxins, decreasing nutrient quality of forage, and altering the distribution of net primary productivity. Such modifications shift dietary resource availability, which in turn affects competition among animals for food. Thus, changes in levels of atmospheric CO2 are likely to have direct effects on the evolution of ecosystems. Our own species, for example, evolved in the "C4 world", one where plants using the C4 photosynthetic makes up 25% of the terrestrial global primary productivity, that has been in place only for the last 6 to 8 million years.
This international symposiums brings together scientists to explore recent developments in deciphering the history of atmospheric CO2, and its consequences on plant and animal evolution. Atmospheric CO2 is rising at a rate unprecedented in human experience, and perhaps unprecedented in Earth's history. This rise, is due to fossil fuel burning and will almost certainly result in significant global warming and ecosystem change.
Much progress has been made in describing the history of CO2. Ice core records show that the glacial and interglacial periods over the last 500,000 years are marked by CO2 concentrations ranging between 180 and 280 ppmV, and thus clearly established the link between atmospheric CO2 and global temperatures. In the 1980s and 1990s Berner and colleagues (Berner 1992, 1997) developed a model for atmospheric CO2 concentrations that linked tectonics, weathering, and other factors. The 1990s saw the development of a number of proxies for CO2 reconstruction, including paleosols (Cerling 1991, Ekart et al., 1999), stomatal densities in leaves (Kurshner et al., 1996; Beerling et al, 1998; Retallack, 2001), alkenones (Pagani et al., 1999), and boron isotopes (Pearson and Palmer, 2000). Together, these models indicate some significant changes in atmospheric CO2, ranging from several thousand ppmV in the Mesozoic to the low values measured in glacial periods.
Along with this development of a CO2 history for the Earth's atmosphere, was the documentation of major changes in terrestrial and marine ecosystems that accompanied many of the significant changes in atmospheric CO2. Berner (1997) has proposed that the rise of vascular plants greatly accelerated silicate weathering reactions, causing further drawdown of CO2 from the atmosphere. The rise of angiosperms occurred while CO2 concentrations were declining in the Cretaceous (Ekart et al., 1999). C4 plants are adapted to low atmospheric CO2 concentrations (< 500 ppmV) where they have a higher quantum yield than do C3 plants (Cerling et al., 1997; Ehleringer et al., 1998); the expansion of C4 ecosystems occurred in a period of low atmospheric CO2 levels, yet the timing does not seem to be associated with any major change in concentration (Pagani et al., 1999).
Meanwhile, studies of modern plants have shown that have a significant response to changing CO2 concentrations, and imply that ecosystems will have a direct response to CO2 concentrations, and also a secondary response due to temperature changes associated with CO2 changes
Concentrations of atmospheric CO2 affect plant nutritional quality resulting in serious consequences for herbivore performance. As CO2 increases, nutritional quality of plants declines as nitrogen contents decrease and carbon to nitrogen ratios increase (Ceulmans and Mousseau 1994, Wilsey 1996, Huges and Bazzaz 1997). In addition, the concentration of plant toxins, particularly phenolics, increase dramatically under elevated CO2 (~650ppm). Such changes in plant quality have direct effects on herbivore performance. In general insect herbivores exhibit decreased performance when fed plants grown under elevated CO2 (Roth and Lindroth 1994, Lawler et al 1997, Stiling et al 1999). Furthermore, some insect herbivores incur greater mortality from predators under elevated CO2 (Stiling et al 1999).
In addition, the enzyme Rubisco. which is responsible for CO2 uptake by plants from the atmosphere, also has a competing oxygenase reaction. This reaction becomes important at high O2/CO2 concentrations (ca. >400) causing photorespirations which results in a decline in the quantum yield of plants using the C3 photosynthetic pathway. C4 photosynthesis using spatial separation of CO2 assimilation and reduction which suppresses the photorespiration reaction. But at a cost – C4 plants have lower nutrient contents that do C3 plants. Animal feeding behavior is directly linked to vegetation changes, and therefore animal evolution is tied to the effect that CO2 has on ecosystems.
Speaker and Poster Schedules (Cliff Lodge, Snowbird Resort, Snowbird, Utah)
Wednesday afternoon, 4:00 pm - 7:00 pm Registration
Wednesday evening, 7:30 pm - 9:30 pm Welcome Social Gathering
Thursday morning, 8:30 am - 1:00 pm Session I: History of atmospheric CO2 and its impact on climate
This session will be devoted to the comparisons of the different paleo-CO2 barometers, including ice core measurements, alkenone and boron isotope studies, and implications for climate change. We will look at the evidence for climate change and its direct relationship to atmospheric CO2 concentrations. Each presentation is 30 minutes.
8:30 - 8:40 Welcome and introduction to symposium 8:40 - 9:20 Thomas Blunier (Atmospheric CO2 data over four climatic cycles from ice cores) 9:20 - 10:00 Robert Berner (The rise of trees and their effect on Phaneozoic CO2) 10:00 - 10:40 Prosenjit Ghosh (CO2 levels in the late Paleozoic and Mesozoic atmosphere) 10:40 - 11:00 coffee break 11:00 - 11:40 Wally Broecker (The role of the ocean in setting the atmosphere's CO2 content) 11:40 - 12:20 Katherine Freeman (CO2 and ecosystem reconstruction using biomarkers) 12:20 - 1:00 Catherine Trudinger (The carbon cycle over the past 1,000 years inferred from inversion of ice core data)
Thursday afternoon, 5:00 pm - 7:40 pm Session II: Impacts of low CO2 on plants
In this session we will look at how plants responded to low atmospheric CO2 concentrations, such as were typical of recent glacial-interglacial cycles. Each presentation is 30 minutes.
4:45 - 5:00 refreshments, coffee, soft drinks 5:00 - 5:40 Alayne Street-Perrot (CO2 and climate as controls on glacial/interglacial changes) 5:40 - 6:20 Rowan Sage (Photosynthetic response to low CO2 concentrations) 6:20 - 7:00 Jed Kaplan (Modeling distributions of C3/C4 plants during glacial/interglacial periods) 7:00 - 7:40 Joy Ward (Evolutionary responses of plants to low CO2 of the late Pleistocene)
Friday morning, 8:30 am - 1:00 pm Session III: Impacts of CO2 on plants and animals
This session will deal with changes in plant chemistry, nutrient content, structure, and form associated with changes in atmospheric CO2 and the implications for the future as CO2 changes in the next century. This session will also explore how animals respond to changes in dietary resources, including changes in chemistry, plant structure, nutrient content, and other factors. Each presentation is 30 minutes.
8:30 - 8:40 Housekeeping and other matters 8:40 - 9:20 David Beerling (Evolutionary responses of plants to CO2 levels) 9:20 - 10:00 Page Chamberlain (Implications of uplift, rock weathering and base cation supply for CO2 sequestration by forests) 10:00 - 10:40 Jim Ehleringer (What controls the abundance of C4 plants?) (Powerpoint) 10:40 - 11:00 coffee break 11:00 - 11:40 Rick Lindroth (Herbivory in an elevated CO2 world) (Powerpoint) 11:40 - 12:20 Denise Dearing (Mammalian herbivory in an elevated toxin world) 12:20 - 1:00 Nick van der Merwe (CO2 and human evolution)
Friday afternoon, 5:00 pm - 7:00 pm Poster session
Friday evening, 7:00 pm - 9:00 pm Symposium Banquet
Saturday morning, 8:30 am - 1:30 pm Session V: Impacts of CO2 at the ecosystem level
Changes in climate, plant chemistry, animal ecology are all tied together at the ecosystem level. This session will explore the relationship of changing atmospheric CO2 to changes in regional or global ecosystems. Each presentation is 30 minutes.
8:30 - 8:40 Housekeeping and other matters 8:40 - 9:20 Robert Harris (Temperature histories from bore-hole thermometry) 9:20 - 10:00 Thure Cerling (Mammalian response to ecosystem change) 10:00 - 10:40 Scott McWilliams (Modern Arctic ecosystems) 10:40 - 11:00 coffee break 11:00 - 11:40 Richard Norby (Modern and future forest ecosystems) (Powerpoint) 11:40 - 12:20 Rebecca Shaw (Modern and future semi-arid ecosystems) 12:20 - 1:00 Dave Schimel (A state-space estimation approach to understanding carbon cycle time scales) 1:00 - 1:30 Symposium wrap up and discussion of volume to be produced
Registration information
If you are interested in registering for this meeting or finding out more about participating in this meeting, please go to the registration page. We invite all interested persons to attend. Opportunities still exist to also present a poster or contribute to one of the oral sessions.
For additional information, please contact Thure Cerling, Denise Dearing, or Jim Ehleringer.
A meeting registration fee of $100 will be required. This fee will include the banquet meal on Friday evening as well as be used to cover the costs associated with refreshments during the poster session and at coffee breaks.
Lodging will be available at $105/evening plus taxes. Lodging will be as double queen-size beds in the Cliff Lodge at Snowbird Ski Resort. All reservations must be made by November 21, 2001 or we risk losing access to the rooms.
