Dissertation/Thesis Abstract

Alternative sampling and analysis methods for digital soil mapping in southwestern Utah
by Brungard, Colby W., M.S., Utah State University, 2009, 283; 1470183
Abstract (Summary)

Digital soil mapping (DSM) relies on quantitative relationships between easily measured environmental covariates and field and laboratory data. We applied innovative sampling and inference techniques to predict the distribution of soil properties, soil attributes, taxonomic classes, and dominant vegetation across a 30,000-ha complex Great Basin landscape in southwestern Utah. This arid rangeland was characterized by rugged topography, diverse vegetation, and intricate geology. Environmental covariates calculated from digital elevation models (DEM) and spectral satellite data were used to represent factors controlling soil development and distribution. We investigated optimal sample size and sampled the environmental covariates using conditioned Latin Hypercube Sampling (cLHS). We demonstrated that cLHS, a type of stratified random sampling, closely approximated the full range of variability of environmental covariates in feature and geographic space with small sample sizes. Site and soil data were collected at 300 locations identified by cLHS. Random forests was used to generate spatial predictions and associated probabilities of site and soil characteristics. Balanced random forests and balanced and weighted random forests were investigated for their use in producing an overall soil map. Overall and class errors (referred to as out-of-bag [OOB] error) were within acceptable levels. Quantitative covariate importance was useful in determining what factors were important for soil distribution. Random forest spatial predictions were evaluated based on the conceptual framework developed during field sampling.

Indexing (document details)
Advisor: Boettinger, Janis L.
Commitee: Tarboton, David G., White, Michael A.
School: Utah State University
Department: Agriculture
School Location: United States -- Utah
Source: MAI 48/02M, Masters Abstracts International
Subjects: Soil sciences, Remote sensing
Keywords: Conditioned Latin hypercube sampling, Digital soil mapping, Great Basin, Optimal sample size, Random forests
Publication Number: 1470183
ISBN: 9781109475913
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