N14C: A plant–soil nitrogen and carbon cycling model to simulate terrestrial ecosystem responses to atmospheric nitrogen deposition

• Published in: Ecological modelling 2012-12, Vol.247, p.11-26
• Main Authors: Tipping, E., Rowe, E.C., Evans, C.D., Mills, R.T.E., Emmett, B.A., Chaplow, J.S., Hall, J.R.
• Format: Article
• Language: English
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Atmospheric deposition; Biological and medical sciences; Carbon; Computer simulation; conifers; denitrification; Deposition; dissolved organic carbon; fractionation; Fundamental and applied biological sciences. Psychology; General aspects; General aspects. Techniques; growing season; herbs; Leaching; Mathematical models; Methods and techniques (sampling, tagging, trapping, modelling...); Nitrogen; nitrogen fixation; NPP; Plants (organisms); Pools; prediction; primary productivity; Radiocarbon; shrubs; simulation models; Soil; Soil (material); soil organic matter; sorption; Synecology; temperature; terrestrial ecosystems; Turnover; vegetation types
• ISSN: 0304-3800; 1872-7026
• DOI: 10.1016/j.ecolmodel.2012.08.002

► N14C is a new model linking soil–plant carbon and nitrogen cycles. ► Its main purpose is to simulate the effects of anthropogenic N deposition. ► N14C has been parameterised with field data for 42 sites in N Europe. ► Results suggest an approximate doubling of NPP due to N deposition. ► Leaching rates of inorganic N depend upon plant type. The dynamic model N14C simulates changes in the plant–soil dynamics of nitrogen and carbon, brought about by the anthropogenic deposition of nitrogen. The model operates with four plant functional types; broadleaved and coniferous trees, herbs and dwarf shrubs. It simulates net primary production (NPP), C and N pools, leaching of dissolved organic carbon and nitrogen (DOC, DON) and inorganic nitrogen, denitrification, and the radiocarbon contents of organic matter, on an annual timestep. Soil organic matter (SOM) comprises three pools, undergoing first-order decomposition reactions with turnover rates ranging from c. 2 to c. 1000 years. Nitrogen immobilisation by SOM occurs if inorganic N remains after plant uptake, and leaching of inorganic N occurs if the immobilisation demand is met. SOM accumulates in the deeper soil by transport and sorption of DOM. Element soil pools accumulate with N inputs by fixation from 12,000 years ago until 1800, when anthropogenic N deposition begins. We describe the parameterisation of N14C with data from 42 published plot studies carried out in northern Europe, plus more general information on N deposition trends, soil radiocarbon, N fixation and denitrification. A general set of 12 parameters describing litter fractionation, N immobilisation, growing season length, DOC and DON leaching, denitrification and NH4 retention was derived by fitting the field data. This provided fair agreements between observations and simulations, which were appreciably improved by moderate (±20%) adjustments of the parameters for specific sites. The parameterised model gives reasonable blind predictions of ecosystem C and N variables from only temperature, precipitation, N deposition, and vegetation type. The results suggest an approximate doubling of NPP due to N deposition, although the majority of the sites remain N-limited. For a given N deposition, leaching rates of inorganic N at conifer and shrub sites exceed those at broadleaf and herb sites.