Terrestrial Ecosystem Model (TEM) Carbon Model

TEM

Authors

Jerry M. Melillo (project coordinator), A. David McGuire, David W. Kicklighter, Yude Pan and Hanqin Tian. The Ecosystems Center, Marine Biological Laboratory, Woods Hole, MA 02543

Links

http://www-eosdis.ornl.gov/NPP/other_files/tem_des.html

http://www.cgd.ucar.edu/vemap/abstracts/TEM.html

http://www.eos-ids.sr.unh.edu/tem.html

http://eco.wiz.uni-kassel.de/model_db/mdb/tem.html

Description

The Terrestrial Ecosystem Model (TEM) is a process-based ecosystem model that describes carbon and nitrogen dynamics of plants and soils for terrestrial ecosystems. This model simulates limitation of GPP by multiple factors. Because plant respiration is explicitly modeled, NPP is simulated as the difference between GPP and carbon respiration. TEM explicitly simulates nitrogen mineralization and immobilization dynamics. However, TEM does not consider the influence of vapor pressure deficit on stomatal conductance or photosynthesis. The TEM uses spatially referenced information on climate, elevation, soils, vegetation and water availability as well as soil- and vegetation-specific parameters to make monthly estimates of carbon and nitrogen fluxes and pool sizes. The response of NPP to elevated CO₂ in TEM is controlled by the control of nitrogen availability on carbon uptake and storage (VEMAP 1995; Pan et al. 1998).

Model scale and resolution

The TEM model operates on a monthly time step. The TEM model is viewed as a global model with a spatial resolution of 0.5 degrees latitude/longitude. This model uses the relatively few compartments, with only one carbon pool apiece for vegetation and soil/litter (two for nitrogen).

Precursors

TEM evolved from an equilibrium model of terrestrial carbon and nitrogen dynamics with hydrological inputs determined by an independent water balance model (WBM, Vörösmarty et al., 1989). This WBM used the same climatic data and soil-specific parameters as TEM. In version 4.0, the algorithms of the WBM were incorporated directly into TEM so that terrestrial carbon, nitrogen and water variables were determined concurrently. TEM 4.1 permits the model to conduct either equilibrium or transient analyses of terrestrial carbon and nitrogen dynamics.

Inputs

Climate variables

1. Monthly temperature (average in degrees C)
2. Monthly total precipitation (cm)
3. Net solar radiation (MJ/m²/d)

Site variables

1. Soil texture
2. Sand, silt, clay (% of rock-free volume)
3. Soil texture
4. Plant nitrogen, phosphorus, and sulfur content
5. Lignin content of plant material
6. Atmospheric and soil nitrogen inputs

Testing and validation

Jenkins et al. (1999) found that TEM predictions were sensitive to regional variations in temperature, but not to soil water holding capacity. Pan et al. (1996) found that differences in solar radiation data sets had the largest effect on TEM estimates of NPP for the conterminous United States.

References

Raich J.W., E.B. Rastetter, J.M. Melillo, D.W. Kicklighter, P.A. Steudler, B.J. Peterson, A.L. Grace, B. Moore III, C.J. Vorosmarty. 1991. Potential net primary productivity in South America: application of a global model. Ecological Applications 1: 399-429.

McGuire A.D., S. Sitch, J.S. Clein, R Dargaville., G. Esser, J. Foley, M. Heimann, F. Joos, J. Kaplan, D.W. Kicklighter, R.A. Meier, J.M. Melillo, B. Moore III, I.C. Prentice, N. Ramankutty, T. Reichenau, A. Schloss, H. Tian, L.J. Williams, U. Wittenberg. 2001. Carbon balance of the terrestrial biosphere in the twentieth century: analyses of CO₂, climate and land-use effects with four process-based ecosystem models. Global Biogeochemical Cycles 15(1), 183-206.

McGuire A.D., J.M. Melillo, L.A. Joyce, D.W. Kicklighter, A.L. Grace, B. Moore III, and C. J. Vorosmarty. 1992. Interactions between carbon and nitrogen dynamics in estimating net primary productivity for potential vegetation in North America. Global Biogeochemical Cycles 6(2), 101-124.

McGuire, A. D., L. A. Joyce, D. W. Kicklighter, J. M. Melillo, G. Esser, and C. J. Vorosmarty, 1993. Productivity response of climax temperature forests to elevated temperature and carbon dioxide: a North American comparison between two global models. Climate Change 24:287-310.

Melillo, J. M., A. D. McGuire, D. W. Kicklighter, B. Moore III, C. J. Vorosmarty, and A. L. Schloss, 1993. Global climate change and terrestrial net primary production. Nature 363: 234-240.

Jenkins, J.C., D.W. Kicklighter, S.V. Ollinger, J.D. Aber and J.M. Melillo. 1999. Sources of variability in NPP predictions at a regional scale: A comparison using PnET-II and TEM 4.0 in northeastern forests. Ecosystems 2: 555-570.