A Sensitivity Analysis of the SPACSYS Model

A - Papers appearing in refereed journals

Shan, Y., Huang, M. B., Harris, P. and Wu, L. 2021. A Sensitivity Analysis of the SPACSYS Model. Agriculture - Basel. 11 (7), p. 624. https://doi.org/10.3390/agriculture11070624

AuthorsShan, Y., Huang, M. B., Harris, P. and Wu, L.

A sensitivity analysis is critical for determining the relative importance of model parameters to their influence on the simulated outputs from a process-based model. In this study, a sensitivity analysis for the SPACSYS model, first published in Ecological Modelling (Wu, et al., 2007), was conducted with respect to changes in 61 input parameters and their influence on 27 output variables. Parameter sensitivity was conducted in a 'one at a time' manner and objectively assessed through a single statistical diagnostic (normalized root mean square deviation) which ranked parameters according to their influence of each output variable in turn. A winter wheat field experiment provided the case study data. Two sets of weather elements to represent different climatic conditions and four different soil types were specified, where results indicated little influence on these specifications for the identification of the most sensitive parameters. Soil conditions and management were found to affect the ranking of parameter sensitivities more strongly than weather conditions for the selected outputs. Parameters related to drainage were strongly influential for simulations of soil water dynamics, yield and biomass of wheat, runoff, and leaching from soil during individual and consecutive growing years. Wheat yield and biomass simulations were sensitive to the 'ammonium immobilised fraction' parameter that related to soil mineralization and immobilisation. Simulations of CO2 release from the soil and soil nutrient pool changes were most sensitive to external nutrient inputs and the process of denitrification, mineralization, and decomposition. This study provides important evidence of which SPACSYS parameters require the most care in their specification. Moving forward, this evidence can help direct efficient sampling and lab analyses for increased accuracy of such parameters. Results provide a useful reference for model users on which parameters are most influential for different simulation goals, which in turn provides better informed decision making for farmers and government policy alike.

KeywordsSensitivity analysis ; Winter wheat; Drainage; Yield; Soil water dynamics; Soil loss; Soil pool
Year of Publication2021
JournalAgriculture - Basel
Journal citation11 (7), p. 624
Digital Object Identifier (DOI)https://doi.org/10.3390/agriculture11070624
Open accessPublished as ‘gold’ (paid) open access
FunderBiotechnology and Biological Sciences Research Council
Funder project or codeS2N - Soil to Nutrition - Work package 2 (WP2) - Adaptive management systems for improved efficiency and nutritional quality
The Rothamsted Long Term Experiments [2017-2022]
Publisher's version
Accepted author manuscript
Output statusPublished
Publication dates
Online01 Jul 2021
Publication process dates
Accepted30 Jun 2021

Permalink - https://repository.rothamsted.ac.uk/item/9867z/a-sensitivity-analysis-of-the-spacsys-model

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