1. General Model Information

Name: Generic Decomposition And Yield

Acronym: GDAY

Main medium: terrestrial
Main subject: forestry, biogeochemistry
Organization level: forest, ecosystem
Type of model: ordinary differential equations
Main application: research
Keywords: carbon dynamics, nitrogen, global, climate change, soil, Farquhar type


Ross McMurtrie
School of Biological Science
University of New South Wales (UNSW)
P.O. Box 1
408, BioScience Building
Kensington, NSW 2033
Tel.: +61-2-9385-3264
Fax: +61-2-9385-1558
Email: r.mcmurtrie@unsw.edu.au



G'DAY (Generic Decomposition And Yield, Comins and McMurtrie 1993) is a generic ecosystem model, which has been used as a tool for analysing the impact of high CO2 on terrestrial ecosystems.
G'DAY is a plant-soil model describing fluxes of C and N among 10 plant, litter and soil compartments. It uses a simplified physiology-based canopy assimilation model to calculate carbon uptake, and the CENTURY model of soil decomposition and N cycling. Carbon uptake is evaluated from absorbed photosynthetically active radiation, multiplied by a light use efficiency e which depends on CO2, air temperature (T), leaf nitrogen concentration [N] and soil water availability. The dependencies of e on CO2, T and [N] are based on Farquhar and colleagues' model of the biochemistry of C3 photosynthesis. Carbon acquired through photosynthesis is allocated to foliage, fine roots and woody tissue in fixed proportions. When plant litter decomposes carbon enters 3 soil pools, active, slow and passive, with decay time constants of order 1-5, 20-50 and 200-2000 years, respectively, as assumed in the CENTURY
model. G'DAY simulates fluxes of N associated with each C transfer, as well as N fluxes due to atmospheric deposition, fixation, nutrient uptake, gaseous emission and leaching.

Abstract taken from GCTE-focus 1 / project Cmeal .

II. Technical Information

II.1 Executables:

Operating System(s):

II.2 Source-code:

Programming Language(s):

II.3 Manuals:

II.4 Data:

III. Mathematical Information

III.1 Mathematics

III.2 Quantities

III.2.1 Input

III.2.2 Output

IV. References

Comins, H.N. and McMurtrie, R.E. 1993.
Long-term response of nutrient-limited forests to CO2-enrichment; equilibrium behaviour of plant-soil models. Ecological Applications. 3: 666-681.
Gower, S.T., McMurtrie, R.E. and Murty, D. 1996.
Aboveground net primary production decline with stand age: potential causes. Trends in Ecology and Evolution (in press).
Kirschbaum, M.U.F., King, D.A., Comins, H.N., McMurtrie, R.E., Raison, R.J., Pongracic, S., Murty, D., Keith, H., Medlyn, B.E., Khanna, P.K. and Sheriff, D.W. 1994.
Modelling forest response to increasing CO2 concentration under nutrient-limited conditions. Plant, Cell and Environment 17: 1081-1099.
McMurtrie, R.E. and Comins, H.N. 1996.
The temporal response of forest ecosystems to doubled atmospheric CO2 concentration. Global Change Biology 2: 49-57.
Murty, D., McMurtrie, R.E. and Ryan, M.G. 1996.
Declining forest productivity in aging forest stands - a modelling analysis of alternative hypotheses. Tree Physiology 16: 187-200.

V. Further information in the World-Wide-Web

Some additional information concerning applications of GDAY might be found here .
The home page of Ross McMurtrie contains information not only on GDAY but also on the models MAESTRO and BIOMASS .

VI. Additional remarks

GDAY is also applied within the ongoing European project ECOCRAFT (climate change impacts on European forests , project leader: P.G. Jarvis).

Last review of this document by: M. Sonntag : October, 18th 1997

Status of the document:
last modified by Tobias Gabele Wed Aug 21 21:44:43 CEST 2002

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