PhD-defence Marcos Angelini
On 6 March 2018, Marcos Angelini successfully defended his PhD-thesis "Structural Equation Modelling for Digital Soil Mapping" (SEM) at Wageningen University. The thesis makes valuable extensions to the basic SEM approach. It extends the modelling and prediction to three-dimensional digital soil mapping using SEM, incorporates model suggestions in a re-specification step, takes a close look at how SEM reproduces covariation between soil properties, explores the extrapolation potential of SEM, and improves SEM predictions by taking a geostatistical approach and kriging SEM residuals. Some of these extensions are truly innovative concludes his promotor Prof. Dr. Gerard Heuvelink: "Dr Angelini, Marcos, did pioneering work by introducing SEM to the digital soil mapping community. His work is already being picked up by others and will certainly have a real impact on the future of digital soil mapping research."
Dr Angelini tested the usefulness of a relatively new statistical technique, known as structural equation modelling (SEM), for digital soil mapping. The attractive feature of SEM is that it bridges the gap between mechanistic and empirical modelling. It starts with a conceptual model based on soil forming process knowledge, translates this into a graphical model, which in turn is associated with a mathematical model. The parameters of the mathematical model are estimated using empirical data.
In his thesis, Dr Angelini explains in detail how SEM works and how it may be applied for digital soil mapping. Dr Angelini used existing data from the National Institute of Agricultural Technology (INTA) in Argentina to calibrate and apply a structural equation model for a case study in the Argentine Pampas. He also applied SEM to a study area in the Great Plains of the USA.
The thesis committee comprised Prof. Dr Rachel Creamer and Dr Willem Kruijer of Wageningen University and Research, Dr Laura Poggio of the James Hutton Institute (Scotland) and Dr Peter Finke of Ghent University (Belgium). The promotor and co-promotor were Prof. Dr Gerard Heuvelink and Dr Bas Kempen of ISRIC – World Soil Information.
Dr Angelini’s research was made possible through the support of INTA (Instituto Nacional de Tecnología Agropecuaria, Argentina), ISRIC – World Soil Information and the Soil Geography and Landscape group of Wageningen University.