Parsimonious modelling of nutrient fluxes for a terrestrial ecosystem on Svalbard
Article Received: 09 June 2005 Accepted: 29 December 2005 Abstract
MBL-MEL, a simple model of ecosystem biogeochemistry, is amended and applied to plant and soil C,
14N and 15N data for the summers of 2001–2003 from Brandalpynten, a maritime high Arctic site on Svalbard following the application of 15N (99 atom%) as 15NO 3-N at or 15NH 4-N at concentrations of 1 or 5 kg N ha −1. Variants of this Parent model are also developed to incorporate: temperature dependence into equations describing nutrient fluxes (Temp model); cryptogams (Cryp model); both features combined (CrypTemp model). Goodness-of-fit (GOF) statistics suggest that the addition of temperature-dependence improves the utility of models with and without cryptogams: the residual weighted sums of squares per data point were 5.69, 3.91, 4.31 and 3.93 for the Parent, Temp, Cryp and CrypTemp models respectively. The application of model selection criteria confirm that the addition of temperature-dependence also improves model generalisability. Across all models, the principal discrepancies between observation and prediction are associated with the inorganic soil 15N pool. We conclude that models in which fluxes are described using simple equations that can be augmented to include additional complexity, are an ideal starting point from which the relationship between GOF and model generalisability can be assessed. Keywords Arctic Complexity Ecosystems Nutrient-cycles Modelling References Akaike, H. 1973 Information theory and an extension of the maximum likelihood principle Petrox, B.N. Caski, F. eds. Second International Symposium on Information Theory Akademiai Kiado Budapest, Hungary 267 Google Scholar Bozdogan, H. 1990 On the information-based measure of covariance complexity and its applications to the evaluation of multivariate linear models Commun. Stat. Theory 19 221 278 Google Scholar Gordon, C., Wynn, J.M., Woodin, S.J. 2001 Impacts of increased nitrogen supply on high Arctic heath: the importance of bryophytes and phosphorus availability New Phytol. 149 461 467 CrossRef Google Scholar Harley, P.C., Tenhunen, J.D., Murray, K.J., Beyers, J. 1989 Irradiance and temperature effects on photosynthesis of tussock tundra Sphagnum mosses from the foothills of the Philip Smith mountains, Alaska Oecologia 79 251 259 CrossRef Google Scholar Joranger, E., Semb, A. 1989 Major ions and scavenging of sulphate in the Norwegian Arctic Atmos. Environ. 23 2463 2469 CrossRef Google Scholar
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