university of florida thesis or dissertation formatting template - Alice

273 Pages·2009·4.95 MB·English

SPATIAL AND SPECTRAL MODELS OF SOIL CARBON AT MULTIPLE SCALES IN
FLORIDA

By

GUSTAVO DE MATTOS VASQUES

A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL
OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT
OF THE REQUIREMENTS FOR THE DEGREE OF
DOCTOR OF PHILOSOPHY

UNIVERSITY OF FLORIDA

2009
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© 2009 Gustavo de Mattos Vasques

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To all Floridians and environmental enthusiasts

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ACKNOWLEDGMENTS
I thank the University of Florida, the Soil and Water Science Department, the Alumni
Fellowship program, and my parents for giving me the opportunity and the resources to conduct
this study. I thank my major advisor Sabine Grunwald for her wise words of advice and guidance
for research and life, and my supervisory committee members Nicholas Comerford, Willie
Harris, Timothy Fik and Wendell Cropper, as well as James Sickman for their guidance and
support. I also thank the Information Technology experts Brandon Hoover, Steve Bloom and
William Deich IV, and my working colleagues from the Geographic Information Systems
Laboratory Jinseok Hong, Brent Myers, Sanjay Lamsal, Rosanna Rivero, Deoyani Sarkhot, Mi-
youn Ann, Jongsung Kim and Ho-young Kwon for their friendship and help. I also thank my
cousins Robert, Sílvia and Luís Cláudio for the love and support that made my stay in the U.S. so
pleasant, my friends in Gainesville for the wonderful talks, parties, trips, laughs, and cries, and
my family in Brazil, who always encouraged me to pursue my dreams, and whom I miss so
much. I give special thanks to my wife and best friend Patricia, whose love, friendship,
enthusiasm, guidance and support were essential in everything that I have accomplished. I cannot
express enough my love for her.
Funding for this doctoral research was provided from various projects including “Linking
Experimental and Soil Spectral Sensing for Prediction of Soil Carbon Pools and Carbon
Sequestration at Landscape Scales” (Cooperative Ecosystem Studies Unit, Natural Resources
Conservation Service, U.S. Department of Agriculture), and “Rapid Assessment and Trajectory
Modeling of Changes in Soil Carbon across a Southeastern Landscape” (National Research
Initiative, U.S. Department of Agriculture).

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TABLE OF CONTENTS

page
ACKNOWLEDGMENTS ...............................................................................................................4
LIST OF TABLES ..........................................................................................................................9
LIST OF FIGURES ....................................................................................................................... 12
ABSTRACT .................................................................................................................................. 15
CHAPTER
1 INTRODUCTION ................................................................................................................. 17
Rationale and Significance ..................................................................................................... 17
Overview ................................................................................................................................ 20
2 COMPARISON OF MULTIVARIATE METHODS FOR INFERENTIAL
MODELING OF SOIL CARBON USING VISIBLE/NEAR-INFRARED SPECTRA ........ 23
Summary ................................................................................................................................ 23
Introduction ............................................................................................................................ 24
Materials and Methods ........................................................................................................... 27
Study Area ...................................................................................................................... 27
Field Sampling ................................................................................................................ 28
Laboratory Analysis ........................................................................................................ 28
Spectroscopy ................................................................................................................... 29
Pre-processing Transformations ..................................................................................... 29
Multivariate Techniques ................................................................................................. 30
Results and Discussion ........................................................................................................... 33
Descriptive Statistics ....................................................................................................... 33
Stepwise Multiple Linear Regression ............................................................................. 33
Principal Components Regression .................................................................................. 34
Partial Least Squares Regression .................................................................................... 35
Regression Tree .............................................................................................................. 36
Committee Trees ............................................................................................................. 38
Variable Selection ........................................................................................................... 39
Pre-processing Transformations ..................................................................................... 39
Conclusions ............................................................................................................................ 41
3 MODELING OF SOIL ORGANIC CARBON FRACTIONS USING VISIBLE/NEAR-
INFRARED SPECTROSCOPY ............................................................................................ 61
Summary ................................................................................................................................ 61
Introduction ............................................................................................................................ 62
Materials and Methods ........................................................................................................... 63
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Field and Laboratory Measurements ............................................................................... 63
Pre-treatment of Soil Spectra and Multivariate Methods ................................................ 65
Results and Discussion ........................................................................................................... 68
Descriptive Statistics ....................................................................................................... 68
Visible/Near-Infrared Spectroscopy Models of Soil Organic Carbon Properties ........... 70
Conclusions ............................................................................................................................ 75
4 BUILDING A SPECTRAL LIBRARY TO ESTIMATE SOIL ORGANIC CARBON
IN FLORIDA ......................................................................................................................... 88
Summary ................................................................................................................................ 88
Introduction ............................................................................................................................ 88
Materials and Methods ........................................................................................................... 91
Study Area ...................................................................................................................... 91
Field and Laboratory Measurements ............................................................................... 92
Soil Scanning and Data Preparation ................................................................................ 93
Multivariate Calibration .................................................................................................. 94
Results and Discussion ........................................................................................................... 97
Descriptive Statistics ....................................................................................................... 97
Performance of the Different Multivariate Calibration Methods .................................... 99
Effect of the Inclusion of Soil Order Data, or Stratification by Soil Order .................. 101
Explanatory Wavelengths for Soil Organic Carbon ...................................................... 102
Conclusions .......................................................................................................................... 103
5 REGIONAL MODELING OF SOIL CARBON AT MULTIPLE DEPTHS WITHIN A
SUBTROPICAL WATERSHED ......................................................................................... 113
Summary .............................................................................................................................. 113
Introduction .......................................................................................................................... 114
Materials and Methods ......................................................................................................... 116
Study Area .................................................................................................................... 116
Field Sampling .............................................................................................................. 117
Laboratory Analysis ...................................................................................................... 118
Comparison of Soil Total Carbon at Different Depths ................................................. 119
Relationship between Soil Total Carbon and Environmental Landscape Factors ........ 119
Scaling-up of Soil Total Carbon in the Santa Fe River Watershed ............................... 120
Results and Discussion ......................................................................................................... 123
Descriptive Statistics ..................................................................................................... 123
Relationship between Soil Total Carbon and Environmental Landscape Factors ........ 125
Scaling-up of Soil Total Carbon in the Santa Fe River Watershed ............................... 131
Conclusions .......................................................................................................................... 138
6 UPSCALING OF DYNAMIC SOIL ORGANIC CARBON POOLS IN A NORTH-
CENTRAL FLORIDA WATERSHED ............................................................................... 153
Summary .............................................................................................................................. 153
Introduction .......................................................................................................................... 153
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Materials and Methods ......................................................................................................... 157
Study Area .................................................................................................................... 157
Field Sampling and Laboratory Methods ...................................................................... 157
Upscaling Methods ....................................................................................................... 158
Results and Discussion ......................................................................................................... 160
Descriptive Statistics ..................................................................................................... 160
Upscaling of Soil Organic Carbon Properties ............................................................... 162
Conclusions .......................................................................................................................... 168
7 INFLUENCE OF GRAIN, EXTENT, AND GEOGRAPHIC REGION ON SOIL
CARBON MODELS IN FLORIDA, USA .......................................................................... 180
Summary .............................................................................................................................. 180
Introduction .......................................................................................................................... 181
Materials and Methods ......................................................................................................... 183
Study Areas, Sampling Designs, and Laboratory Methods .......................................... 183
The state of Florida ................................................................................................ 184
The Santa Fe River watershed ............................................................................... 186
The University of Florida Beef Cattle Station ....................................................... 187
Conversion of Soil Organic Carbon Measurements to Soil Total Carbon .................... 188
Calculation of Profile Soil Total Carbon at 0-100 cm .................................................. 188
Regression Modeling of Soil Total Carbon .................................................................. 189
Preparation of soil total carbon data ...................................................................... 190
Preparation of environmental Geographic Information System layers .................. 191
Evaluating the influence of grain ........................................................................... 192
Evaluating the influence of extent ......................................................................... 193
Evaluating the influence of geographic regions ..................................................... 194
Results and Discussion ......................................................................................................... 194
Descriptive Statistics ..................................................................................................... 194
Influence of Grain on Soil Total Carbon Regression Models ....................................... 195
Transferability of Soil Total Carbon Regression Models across Grains ....................... 198
Influence of Extent on Soil Total Carbon Regression Models ...................................... 199
Transferability of Soil Total Carbon Regression Models across Extents ..................... 200
Influence of Geographic Region on the Distribution of Soil Total Carbon .................. 201
Transferability of Soil Total Carbon Regression Models across Geographic Regions . 202
Conclusions .......................................................................................................................... 205
8 MULTI-SCALE BEHAVIOR OF SOIL CARBON AT NESTED REGIONS IN
FLORIDA, USA .................................................................................................................. 221
Summary .............................................................................................................................. 221
Introduction .......................................................................................................................... 222
Materials and Methods ......................................................................................................... 225
Study Area .................................................................................................................... 225
Field Sampling and Laboratory Analysis ...................................................................... 226
Characterization of the Spatial Dependence of Soil Total Carbon ............................... 228
Results and Discussion ......................................................................................................... 229
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Descriptive Statistics ..................................................................................................... 229
Spatial Dependence of Soil Total Carbon ..................................................................... 230
Variogram analysis ................................................................................................ 230
Fractal analysis ...................................................................................................... 233
Conclusions .......................................................................................................................... 236
9 SYNTHESIS AND OUTLOOK .......................................................................................... 247
LIST OF REFERENCES ............................................................................................................ 256
BIOGRAPHICAL SKETCH ....................................................................................................... 273

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LIST OF TABLES
Table page

2-1 Investigations on diffuse reflectance spectroscopy of soil carbon and soil organic
matter. ................................................................................................................................ 42
2-2 Pre-processing transformations applied to the spectral curves of soil samples. ................ 45
2-3 Soil total carbon (TC) and log-transformed TC (LogTC) descriptive statistics for the
whole dataset, calibration set, and validation set. ............................................................. 46
2-4 Summary statistics for the spectral models of log-transformed soil total carbon
(LogTC) produced by stepwise multiple linear regression (SMLR). ................................ 47
2-5 Descriptive statistics of predicted log-transformed soil total carbon (LogTC) for the
calibration and validation sets for the best models obtained from the five multivariate
calibration techniques tested. ............................................................................................ 48
2-6 Summary statistics for the spectral models of log-transformed soil total carbon
(LogTC) produced by principal components regression (PCR). ....................................... 49
2-7 Summary statistics for the spectral models of log-transformed soil total carbon
(LogTC) produced by partial least squares regression (PLSR). ........................................ 50
2-8 Summary statistics for the spectral models of log-transformed soil total carbon
(LogTC) produced by regression tree (RT). ...................................................................... 51
2-9 Summary statistics for the spectral models of log-transformed soil total carbon
(LogTC) produced by committee trees (CT). .................................................................... 52
3-1 Descriptive statistics of measured soil organic carbon properties. .................................... 77
3-2 Pearson’s correlation coefficients between the measured soil organic carbon
properties. .......................................................................................................................... 79
3-3 Summary statistics of the models obtained for each soil organic carbon property by
the different multivariate methods, associated with their respective best pre-
processing transformations. ............................................................................................... 80
3-4 Summary statistics of the models obtained for each soil organic carbon fraction by
simple linear regression, and by partial least squares regression, using both soil
reflectance and LogTC as predictors. ................................................................................ 82
4-1 Descriptive statistics of soil organic carbon (SOC) and ln-transformed SOC
(LnSOC) for the whole dataset, and stratified soil horizons. .......................................... 105
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4-2 Summary statistics for the spectral models of soil organic carbon (SOC) produced by
committee trees (CT). ...................................................................................................... 106
4-3 Summary statistics for the spectral models of ln-transformed soil organic carbon
(LnSOC) produced by partial least squares regression (PLSR). ..................................... 107
5-1 Environmental data and sources used to model the global spatial trend of log-
transformed soil total carbon (LogTC). ........................................................................... 140
5-2 Descriptive statistics of observed soil total carbon (TC) and log-transformed TC
(LogTC) at different depths. ............................................................................................ 142
5-3 Pair-wise comparison of log-transformed soil total carbon (LogTC) at different
depths. ............................................................................................................................. 144
5-4 Analyses of variance (ANOVA) between log-transformed soil total carbon at 0-100
cm (LogTC100) and selected environmental variables. .................................................. 145
5-5 Homogeneous groups of log-transformed soil total carbon at 0-100 cm (LogTC100)
based on land use/land cover, soil order, soil drainage class, and geologic unit,
respectively, according to Dunnett’s T3 test at the 0.05 confidence level. ..................... 146
5-6 Comparative results of the three geostatistical methods used to model soil total
carbon (TC) at different depths. ...................................................................................... 147
5-7 Semivariogram parameters of the fitted exponential model of the best geostatistical
method identified for soil total carbon (TC) at each depth. ............................................. 148
6-1 Descriptive statistics of measured soil organic carbon (C) properties. ........................... 171
6-2 Comparative results of the three geostatistical methods used to model soil organic
carbon (C) properties at 0-30 cm. .................................................................................... 173
6-3 Stepwise multiple linear regression (SMLR) models, and variables selected by
regression tree (RT) models of the global trend of soil organic carbon (C) properties. .. 174
6-4 Semivariogram parameters of the fitted exponential models of the soil organic
carbon (C) properties. ...................................................................................................... 175
7-1 Environmental Geographic Information Systems (GIS) layers used as explanatory
variables in the stepwise multiple linear regression models of soil total carbon. ............ 209
7-2 Descriptive statistics of soil total carbon (TC) and ln-transformed TC (LnTC) at the
three study areas. ............................................................................................................. 210
7-3 Regression coefficients and goodness-of-fit statistics of the stepwise multiple linear
regression model of ln-transformed soil total carbon in ln% derived at different
grains in the Santa Fe River watershed. .......................................................................... 211
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