Global Warming Potentials And Degradation Rate Assessment Of Soils Of Selected Flood Plains In Imo State
ABSTRACT
This study investigated the Global Warming Potentials (GWPs),
degradation rate and erodibility status of soils of selected floodplains in Imo
State. A target soil survey technique was adopted and the experimental design
was a 5x3 factorial experiment laid out in a randomized complete block design.
The factors were floodplain and soil depth. Five floodplains were selected.
They were Obiakpu, Mmahu, Amuzu, Umuneke and Orsu obodo. Five minipedons were dug randomly in each
floodplain and soils were sampled at depths of 0-20 cm, 20-40 cm and 40-60 cm.
A total of 75 soil samples were collected from the study area and taken to the
laboratory for analyses. Climate data of average monthly temperature and
average monthly precipitation of the study area for a period of 30 years (1987
to 2016) were also analysed. Results showed that the
area had a preponderance of sand fraction which ranged from 694 g/kg to 856
g/kg while clay content ranged from 105 g/kg to 191 g/kg. The textural classes
of the soils of the study area ranged from sandy loam to loamy sand. Bulk
density was moderate to high and ranged from 1.48 g/cm3 to 1.60 g/cm3.
Total porosity ranged from 39.80 % to 44.13 %. The hydraulic conductivity
values were moderate to slow. The results of the field capacity, permanent
wilting point, saturation capacity and available water capacity were generally
low. The soils also had moderate permeability. Results of the soil chemical
properties showed that the soil pH were strongly acidic. Organic carbon ranged
from 0.29 to 19.87 g/kg with the least in Orsu obodo and the highest in
Obiakpu, total nitrogen ranged from 0.22 to 1.84 g/kg, available phosphorus
ranged from 2.62 to 11.88 mg/kg. The
basic cations were also low in the study area. The TEB ranged from 3.62 to
11.87 Cmol/kg. The TEA ranged from 1.09 to 2.33 Cmol/kg. The ECEC ranged from
5.71 to 12.91 Cmol/kg. Obiakpu and Mmahu were more stable and less prone to
erosion than the other locations. Assessment of physical degradation rate of
the study area showed that 80 % of the soils of the study area were moderately
degraded while 20 % were none or slightly degraded. For the chemical
degradation, Obiakpu and Mmahu were none to slightly degraded while the other
floodplains had varying degrees of degradation. Regression of average
temperature and rainfall with time revealed that in Imo State, the mean annual
temperature is increasing by 0.02oC while the annual rainfall totals
is reducing by 13.50 mm annually indicating global warming and desert
encroachment. Results of GHG emissions showed that CO2 flux was
higher than CH4 flux in the study area and ranged from 29,365.47
kg/ha/yr to 40,337.37 kg/ha/yr, and the CH4 flux ranged from 1097.35
kg/ha/yr to 1440.62 kg/ha/yr while the net flux of CO2 and CH4
ranged from 30462.82 to 41777.99 kg/ha/yr. The GWP values followed similar
pattern. GWP for CO2 ranged from 96745.33 to 655352.23kg/ha/yr, GWP
for CH4 ranged from 11805.53 to 144473.81kg/ha/y. It was therefore
recommended that more trees and crops should be grown in the study area to
sequester carbon, and flood control measures should also be heightened.
Cover
Page
Title Page i
Declaration ii
Dedication iii
Certification iv
Acknowledgement v
Table
of Contents vi
List
of Tables xiii
List
of Figures xiv
Abstract xv
CHAPTER
1: INTRODUCTION 1
CHAPTER 2: LITERATURE REVIEW 4
2.1 Flooding in Nigeria 4
2.2 Causes of Flooding 5
2.3 Types of Flood 6
2.4 Climate Change and Global Warming 8
2.4.1 Definition of climate change 8
2.4.2 Causes of increase in global surface
temperatures and changing climatic patterns 9
2.5 Soil Ecosystem Green House Gaseous
Exchange 11
2.6 Flooding and Green House Gas Emissions 13
2.7 Drivers of Green House Gas Emissions from
soils 13
2.7.1 Temperature 15
2.7.2 Humidity 16
2.7.3 Nutrients 17
2.7.3a Soil physical fertility 18
2.7.3b Soil chemical fertility 18
2.7.3c Soil biological fertility 19
2.7.4 Vegetation 20
2.7.5 Land use and land cover 21
2.8 Atmospheric Temperature, Soil Temperature
and Greenhouse Gas Emissions 22
2.9 Methodologies to Quantify GHG Emissions from
Soils 23
2.9.1 Chamber systems 25
2.9.1a Closed chambers 25
2.9.1b Open chambers 26
2.9.2 Micrometeorological methods 26
2.9.3 Remote sensing 27
2.9.4 Modeling of soil green house gas emissions 27
2.10 Effects of Climate Change on Crop Yield 28
2.10.1 Effects of increased
atmospheric CO2 on crop production 29
2.10.2 Effects of
temperature alterations on crop production 30
2.10.3 Effects of
precipitation regime changes on crop production 31
2.11 Importance of
Mitigating the Emission of Green House Gases From Soils 32
2.12 United Nations’ Plan to Combat Climate
Change 34
2.13 Great Green Wall Accelerator Initiative 34
CHAPTER 3 MATERIALS AND METHODS 38
3.1 Description of Study Area 38
3.1.1 Location of study area 38
3.1.2 Climate of study area 38
3.1.3 Geology and geomorphology of the study area 39
3.1.4 Relief of the study area 39
3.1.5 Drainage of the study area 44
3.1.6 Socio-economic activities in the study area 47
3.1.7 Vegetation of the study area 47
3.2 Pre-Field Studies 48
3.3 Field Studies 49
3.4 Climatic Parameters 49
3.5 Laboratory
Analyses 50
3.5.1 Soil meteorological properties 50
Net Ecosystem Exchange 50
Global Warming Potential (GWP) 50
3.5.2 Soil physical properties 51
Particle size distribution 51
Silt/clay ratio 51
Soil bulk density 51
Total porosity 52
Saturated hydraulic conductivity 52
Soil permeability 52
Soil erodibility 53
3.5.3 Soil
chemical properties 54
Soil pH 54
Soil organic carbon 54
Soil organic matter 54
Total organic carbon stock 54
Total nitrogen 55
Available phosphorus 55
Exchangeable acidity 56
Percentage aluminium saturation 56
Electrical conductivity 56
Exchangeable
bases 56
Effective cation
exchange capacity 56
Percentage base
saturation 57
3.6 Soil Elemental Ratios 57
Exchangeable
sodium percentage 57
3.7 Soil Degradation Assessment 57
Land degradation assessment by
direct approach 57
Land degradation assessment by
indirect approach 58
3.8 Experimental Design, Data Presentation and
Analyses 60
Experimental design and data
presentation 60
Data analyses 60
Spatial analyses 60
CHAPTER 4 RESULTS AND DISCUSSIONS 62
4.1 Physical Properties of the Soils of the
Study Area 62
Particle size distribution of the
soils of the study area 62
Silt/clay ratio 64
Total porosity 65
Bulk density 66
4.2 Moisture Properties of the Soils of the
Study Area 67
Saturated hydraulic conductivity 67
Field capacity 67
Permanent wilting point 69
Available water capacity 69
Saturation capacity 70
4.3 Permeability Classes of the Soils of the
Study Area 70
4.4 Soil Chemical Properties 72
Soil organic carbon 72
Total nitrogen 72
Available phosphorus 74
Soil pH 75
Electrical conductivity 75
Exchangeable basic cations 75
Exchangeable aluminium 78
Exchangeable hydrogen 78
Total exchangeable acidity 79
Effective Cation Exchange Capacity 80
Base saturation 81
4.5 Soil Organic Carbon Stock and Soil
Microbial Carbon Contents in the Study Area 82
Soil organic carbon stock 82
Soil microbial carbon 82
4.6 Elemental Ratios of the Soils of the
Study Area as Soil Fertility Indexes 84
Carbon: Nitrogen ratio 84
Calcium: Magnesium ratio 84
Potassium: Magnesium ratio 86
Nitrogen: Potassium ratio 86
Exchangeable Sodium Percentage (ESP) 87
4.7 Erodibility of the Soils of the Study
Area 88
Dispersion ratio 88
Clay dispersion ratio 90
Clay Flocculation Index 90
Aggregated Silt Plus Clay 91
4.8 Land Degradation Assessment 91
4.8.1 Land degradation assessment by direct
approach 91
Physical degradation 93
Chemical degradation 93
Biological degradation 94
4.8.2 Land degradation assessment using land
degradation index values 94
4.9 Results of the Climatic Parameters of the
Study Area 99
Maximum temperature 99
Minimum temperature 99
Temperature range 100
Annual rainfall 100
4.10 Trend Analysis of Climate Parameters in the
Study Area 106
4.11 Relationship between Climatic Variables
with Time 108
4.12 Estimation of Change in Mean Annual
Temperature 109
4.13 Estimation of Change in Mean Annual
Rainfall 109
4.14 Relationship between Air Temperature and
Soil Temperature at Different Depths 110
4.15 Green House Gas (GHG) Fluxes in the Study Area 114
CO2 flux 114
CH4 flux 114
Net green house gas fluxes 114
4.16 Global Warming Potentials (GWPs) of the
Soils of the Study Area 117
Global warming potentials for CO2 117
Global warming potentials for CH4 117
Net global warming potentials in the
study area 118
4.17 Correlation Results of Erodibility Indices
with Selected Soil Properties 121
Correlation of Dispersion Ratio with
other soil properties 121
Correlation of Clay Dispersion Ratio
(CDR) with other soil properties 121
Correlation of Aggregated Silt and
Clay (ASC) with other soil properties 123
Correlation of Clay Flocculation
Index (CFI) with other soil properties 124
4.18 Correlation between Green House Gases and
Global Warming Potentials with Soil Physical and Chemical Properties 125
4.18a Correlation of Green House Gases with other soil
Properties 125
CO2 fluxes with other
soil properties 125
CH4 fluxes with other
soil properties 125
Net Green House Gas fluxes of CO2
and CH4 with selected soil properties 127
4.18b Correlation of soil Global Warming Potentials
with selected soil properties 127
Global Warming
Potential for CO2 127
Global Warming
Potential for CH4 129
Net Global
Warming Potentials for CO2 and CH4 130
4.19 Multiple Linear
Regression Models of GHGs with Selected Soil Properties 131
4.20 Multiple Linear
Regression Models of GWPs with Selected Soil Properties 134
4.21 Principal Component Analysis 137
4.22 Spatial Structure
of Green House Gas fluxes and Global Warming Potentials from the Soils of the
Study Area 141
4.22a Spatial structure of Green House Gas fluxes 141
Spatial structure of soil CO2
fluxes in the study area 141
Spatial structure of soil CH4
fluxes from the soils of the study area 141
4.22b Spatial structure of Global Warming
Potentials of the soils of the study area 144
Spatial structure of Global Warming
Potentials for soil CO2 fluxes in the study area144
Spatial structure of Global Warming
Potentials for soil CH4 fluxes in the study area144
4.23 Krigged Maps of
Green House Gas fluxes in the Study Area 146
Krigged Map of soil CH4 fluxes in the study area 146
Krigged Map of soil CO2
fluxes in the study area 146
4.24 Krigged
Maps of Global Warming Potentials in the Study Area 149
Krigged map of soil
GWPCO2 in the study area 149
Krigged map of soil
GWPCH4 in the study area 149
CHAPTER 5 SUMMARY, CONCLUSION AND
RECOMMENDATIONS 152
5.1 Summary 152
5.2 Conclusion 155
5.3 Recommendations 156
REFERRENCES 158
APPENDICES 179
LIST OF TABLES
3.1 Permeability classes of soils 53
3.2 Indicators and criteria for degradation
of soils 59
4.1 Physical properties of the soils of the
study area 63
4.2 Moisture properties of the soils of the
study area 68
4.3 Permeability classes of the soils of the
study area 71
4.4 Chemical properties of the soils of the
study area 73
4.5 Soil organic carbon stock and soil
microbial carbon of the soils of the study area 83
4.6 Elemental ratios of the soils of the
study area 85
4.7 Erodibility Indices of the soils of the
study area 89
4.8a Land Degradation ratings using direct
approach 93
4.8b Land degradation indices of the soils of
the study area 95
4.9 Mean monthly climate data of the study
area (1987 to 2016) 101
4.10 Mean Decadal Variation of climatic
variables of the study area 102
4.11 Trend analyses of the climatic parameters
in the study area 107
4.12 Relationship between Climatic Variables
with Time 108
4.13 Air temperature and soil temperature at
different depths 111
4.14 Multiple Linear Regression of Air Temperature
with Soil Temperature 112
4.15 Green House Gas Fluxes in the Study Area 116
4.16 Global Warming Potentials of the soils of
the study area 119
4.17 Correlation between erodibility indices and
other soil properties 122
4.18a Correlation between Green House Gases with
selected soil properties 126
4.18b Correlation between Global Warming Potentials
with selected soil properties 128
4.19 Multiple Linear Regression of Green house
gases (GHGs) with selected soil properties in the Study Area 133
4.20 Multiple Linear Regression of Global
Warming Potentials (GWPs) with selected soil properties in the Study Area 136
4.21 Rotated Principal
Component Analysis (PCA) results 139
LIST OF FIGURES
2.1 Key drivers of GHG emissions from soil 14
2.2 Overview of methodologies for measuring of green house
gas emissions from soils25
3.1 Map of
Imo State showing study areas 41
3.2 Geologic Map of
the study area 42
3.3 Relief Map of the study area 43
3.4 Map showing the five major sub basins in
Imo State 45
3.5 Drainage Map of the study area 46
4.1 Maximum temperature against months 103
4.2 Minimum temperature against months 104
4.3 Diurnal temperature range against months 105
4.4 Green house gas emissions from the soils
of the study area 120
4.5 Global warming potentials of the soils of
the study area 120
4.6 Semivariogram for CO2 143
4.7 Semivariogram for CH4 143
4.8 Semivariogram
for GWPCO2 145
4.9 Semivariogram for GWPCH4 145
4.10 Krigged Map of
Soil CH4 flux in the study area 147
4.11 Kriggeed Map of
Soil CO2 flux in the study area 148
4.12 Krigged Map of
Global Warming Potentials of CO2 in the study area 150
4.13 Krigged Map showing the distribution of
Global Warming Potentials of CH4 in the study area 151
0.0
MICHAEL, A (2023). Global Warming Potentials And Degradation Rate Assessment Of Soils Of Selected Flood Plains In Imo State. Repository.mouau.edu.ng: Retrieved Oct 31, 2025, from https://repository.mouau.edu.ng/work/view/global-warming-potentials-and-degradation-rate-assessment-of-soils-of-selected-flood-plains-in-imo-state-7-2
AKANINYENE, MICHAEL. "Global Warming Potentials And Degradation Rate Assessment Of Soils Of Selected Flood Plains In Imo State" Repository.mouau.edu.ng. Repository.mouau.edu.ng, 10 Aug. 2023, https://repository.mouau.edu.ng/work/view/global-warming-potentials-and-degradation-rate-assessment-of-soils-of-selected-flood-plains-in-imo-state-7-2. Accessed 31 Oct. 2025.
AKANINYENE, MICHAEL. "Global Warming Potentials And Degradation Rate Assessment Of Soils Of Selected Flood Plains In Imo State". Repository.mouau.edu.ng, Repository.mouau.edu.ng, 10 Aug. 2023. Web. 31 Oct. 2025. < https://repository.mouau.edu.ng/work/view/global-warming-potentials-and-degradation-rate-assessment-of-soils-of-selected-flood-plains-in-imo-state-7-2 >.
AKANINYENE, MICHAEL. "Global Warming Potentials And Degradation Rate Assessment Of Soils Of Selected Flood Plains In Imo State" Repository.mouau.edu.ng (2023). Accessed 31 Oct. 2025. https://repository.mouau.edu.ng/work/view/global-warming-potentials-and-degradation-rate-assessment-of-soils-of-selected-flood-plains-in-imo-state-7-2