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Digital soil mapping of an Argentinian Pampa Region using structural equation modelling.
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Transcript of Digital soil mapping of an Argentinian Pampa Region using structural equation modelling.
Digital soil mapping of an Argentinian Pampa Region using structural equation modelling
15th September 2015Marcos E. Angelini, Gerard B.M. Heuvelink, Bas Kempen, Hector J.M. Morrás, Darío Rodríguez
Introduction
Interrelationships between soil properties are essential to
understand soil dynamics
Soil properties are usually predicted individually in
DSM
Our goal is to model the soil system interrelationships
Structural equation modelling (SEM)A scientific framework to analyse cause-effect connections in a system (Grace, 2006)
SEM essentials Path analysis, factor analysis & simultaneous equation
systems, starting point is a conceptual model Extension of conventional regression techniques Measurement error explicitly included Recursive paths allowed (Y-> X, X -> Y)
~23 000 km2
Phaeozems and Solonetz
320 soil profiles for model calibration
100 soil profiles for validation (stratified random sampling)
Case study: application of SEM to Argentinian Pampa
Conceptual model
1. Bases saturation2. Total Bases 3. Ratio Clay % of B/A horizons4. OC A horizon5. ESP A horizon6. ESP B horizon7. Thickness A horizon
From graphical to mathematical model
𝜂=𝛽⋅𝜂+𝛾 ⋅Χ+𝜁Structural model
Measurement model
𝛽 𝛽
𝛽
𝛾𝛾𝛾
𝛾𝛾𝛾𝛾
𝜆𝑦
𝜆𝑦
𝜆𝑦
SEM outcome (preliminary results)
lavaan & semPlot R packages
%OC A horizon (preliminary results)
R-squared 0.249
Predictors EstimateMean LST 0.375 ***SD EVI 0.296 ***Terrain Index 0.116 . SD LST 0.110 .
R-squared 0.448
Predictors EstimateMean LST -0.330 *** SD EVI 0.198 *** SD LST 0.212 ** ESP A hor. -1.374 . Terrain Index 0.171
Structural Equation Model Linear Regression Model
Final remarks
• SEM is a promising approach to model interrelationships in DSM
• SEM allows to include expert and process knowledge
• Next steps to check and validate preliminary results, as well as apply non-linear relationships and categorical variables
Thanks!