This project is designed to address the question of the quantitative relationship between increasing CO2 concentrations and carbon sequestration in terrestrial ecosystems. The current increase in atmospheric concentration of CO2 is considered to be one of the most important long-term changes occurring on this planet. This is reflected in the recent NERC announcement that increased understanding of the carbon budget is a key scientific challenge and priority issue for NERC science over the next five years. The Intergovernmental Panel on Climate Change identified creation and strengthening of carbon sinks in the soil as a clear option for increasing removal of CO2 from the atmosphere. Enhanced sequestration of atmospheric CO2 in the soil, ultimately as stable soil organic matter, provides a more lasting solution than sequestering CO2 in standing biomass.
Carbon sequestration at the ecosystem level is the complex resultant of plant photosynthesis, respiration, growth, litter production, root exudation, decomposition and other processes. This project will unravel some of these multiple interactions. An often overlooked but significant part of the carbon budget is the emission of volatile organic compounds by plants, which we will study as well. These compounds have important roles to play in the tropospheric chemistry of ozone and aerosols.
Experiments investigating the responses of vegetation to elevated CO2 concentration have usually been performed at only two concentrations, typically at current ambient and twice-ambient concentration, providing no information about the shape of the response curve between these two points. The shape is likely to be influenced by the supply of soil nutrients. Therefore, this project will measure responses of six carefully selected woody species of contrasting nature under a suite of four CO2 concentrations and two soil nutrient levels. The experimental approach utilises the natural differences in the frequency of two carbon isotopes (12C and 13C) between so-called C3 and C4 plants, and the soils which have developed beneath them, to quantify carbon inputs to soils. This is achieved by growing our C3 plants in a "C4 soil", i.e. a soil which has supported the growth of C4 grassland for a very long time. The current project will test the hypothesis that increased concentrations of CO2 will lead to increased net carbon storage in soil/vegetation systems. We also hypothesise that effects on net carbon storage will be strongly correlated with plant growth responses to elevated CO2, and we will test this subsidiary hypotheses by comparing putative high- and low-response tree species.
Additional hypotheses are the subject of two tied
Funded by the Natural Environment Research Council (NERC)
G. Kerstiens (Department of Biological Sciences, Lancaster University) and P. Ineson (Department of Biology, University of York)
J. Heath (Air Pollution and Climate Change Unit, Department of Biological Sciences, Lancaster University)
Additional supervisors of tied PhD studentships:
C. N. Hewitt and R. D. Bardgett (Lancaster University), H. Black (CEH Merlewood)
Edward Ayres, Malcolm Possell
Jean-Marc Guehl (INRA Centre de Nancy, France), Clenton Owensby (Kansas State University, USA), Andy Stott and Darren Sleep (Stable Isotope Facility, CEH Merlewood)
Last update: 04/02/2002