Introduction

Keeling Plot Isotope

Measurements of ecosystem respiration Reco) provide an estimate of carbon losses, a critical component of the ecosystem carbon balance. These measurements most often integrate respiratory activity from a wide range of sources including aboveground leaves and stems and belowground roots and microorganisms. Each of these sources can potentially respond to environmental conditions in unique ways and at different timescales. As the greater part of carbon dioxide (co2) fixed during photosynthesis is...

References

J., Marland G., Boden T. and Bischof S. (2000) Carbon dioxide emissions from fossil fuel consumption and cement manufacture, 1751-1991, and an estimate of their isotopic composition and latitudinal distribution. In The Carbon Cycle (T. M. L. Wigley and D. S. Schimel, eds) pp. 53-62. Cambridge University Press, Cambridge. Barbosa P. M., Stroppiana D., Gregoire J. M. and Pereira J. M. C. (1999) An assessment of vegetation fire in Africa (1981-1991) Burned areas, burned biomass, and...

What Determines the S13C of Heterotrophic Soil Respiration

The 13C of soil organic matter SOM is originally dependent on the average 13C of plant photosynthates at the site. Balesdent el al 1993 proposed, therefore, that the SOM at dry sites should have a higher 13C than at wet sites. Data on the lt 513C of the soil C from a range of sites in Oregon were consistent with this hypothesis Bowling et al, 2002 . However, there are circumstances when other factors influencing C Ca may be more important, for example N supply, as discussed below. It is also...

Graphical Means to Understanding the Global Atmospheric Budget Robin Hood Diagrams

Here I provide a step-by step description of each vector in a Robin Hood diagram of the global atmospheric carbon budget Fig. 13.2 . The budget and figure is constructed arbitrarily for the year 1990. This vector approach is referred to as a Robin Hood diagram because of the abundance of arrows Inez Fung, personal communication, 2000 and the overall process of solving for land and ocean carbon sinks using 13C02 and 12C02 is known as a 'double deconvolution' Heimann and Keeling, 1989 . In the...

The Isotopic Composition of Urban CO2 Sources

The isotopic composition of fossil fuel emissions is of great interest in atmospheric studies of the carbon cycle as well as local studies of urban CO2 sources Andres et al., 2000 . Emissions of CO2 from fossil fuel combustion are naturally more depleted in 13C than is atmospheric co2, and cause 13C dilution of the atmosphere Keeling et al., 1979 . In order to utilize isotopic tracers to estimate the role of biological uptake of atmospheric CO2 at the global scale, the contributions of fossil...