The seasonal exchange of carbon dioxide between the atmosphere and the terrestrial biosphere : extrapolation from site-specific models to regional models

Author

Anthony W. King

Date of Award

12-1986

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major Professor

Arthur C. Echternacht

Committee Members

D. L. DeAngelis, R. V. O'Neill, L. J. Gross, E. C. Clebsch

Abstract

Ecological models of the seasonal exchange of carbon dioxide (CO₂) between the atmosphere and the terrestrial biosphere are needed in the study of changes in atmospheric CO₂ concentration. In response to this need, a set of site-specific models of seasonal terrestrial carbon dynamics was assembled from open-literature sources. The collection was chosen as a base for the development of biome-level models for each of the earth's principal terrestrial biomes or vegetation complexes. The primary disadvantage of this approach is the problem of extrapolating the site-specific models across large regions having considerable biotic, climatic, and edaphic heterogeneity. Two methods of extrapolation were tested.

The first approach was a simple extrapolation that assumed relative within-biome homogeneity, and generated CO₂ source functions that differed dramatically from published estimates of CO₂ exchange. The differences were so great that the simple extrapolation was rejected as a means of incorporating site-specific models in a global CO₂ source function.

The second extrapolation explicitly incorporated within-biome variability in the abiotic variables that drive seasonal biosphere-atmosphere CO₂ exchange. Simulated site-specific CO₂ dynamics were treated as a function of multiple random variables (i.e., the model driving variables). The predicted regional CO₂ exchange is the computed expected value of simulated site-specific exchanges for that region times the area of the region. The extrapolation was tested for the circumglobal latitude belt between 64°N and 90°N. The test involved the regional extrapolation of a tundra and a coniferous forest carbon exchange model. Comparisons between the CO₂ exchange estimated by extrapolation and published estimates of regional exchange for the latitude belt support the appropriateness of extrapolation by expected value. Extrapolation by mathematical expectation is a promising technique for extrapolating from site-specific models to regional and biome-level models.

Recommended Citation

King, Anthony W., "The seasonal exchange of carbon dioxide between the atmosphere and the terrestrial biosphere : extrapolation from site-specific models to regional models. " PhD diss., University of Tennessee, 1986.
https://trace.tennessee.edu/utk_graddiss/12278