Modelling C and N dynamics in forest soils with a modified version of the CENTURY model

The CENTURY model of soil organic matter turn-over developed by Parton and co-workers has been used successfully for grasslands to predict dynamics of C, N and other nutrients. It was tested here for decomposition of a range of forest litters and for N mineralisation in forest soils. Modifications to the CENTURY model were necessary to match model output to empirical findings. These modifications included: (1) incorporation of additional woody litter pools (i.e. fine-wood and coarse-wood) (2) allowing the N content of soil organic matter (SOM) pools to vary (3) constraining N mineralisation and immobilisation to the active SOM pool (4) incorporation of a small flux of mineral N to the resistant SOM pool (5) allowance of mycorrhizal uptake of N, and (6) re-formulation of temperature and moisture effects on decomposition. Other possible changes, such as giving greater flexibility to the critical N concentration for mineralisation, were tested but found not to improve model performance. The modified model largely accounted for the effects of initial lignin and N concentration on subsequent litter decomposition rate, litter N concentrations and critical N concentrations for the commencement of mineralisation. Consequently, the model could successfully simulate realistic time courses of N immobilisation and subsequent mineralisation for a range of litter types. The present model also successfully predicted the critical N concentration for N mineralisation across a wide range of litter samples from forests and other vegetation sources. Net mineralisation was successfully simulated in forest soils, which were either untreated, irrigated or fertilised. (C) 2002 Elsevier Science Ltd. All rights reserved.