Global Warming Potentials And Degradation Rate Assessment Of Soils Of Selected Flood Plains In Imo State
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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.
TABLE OF CONTENTS
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
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APA
AKANINYENE, M., & OKON (2023). Global Warming Potentials And Degradation Rate Assessment Of Soils Of Selected Flood Plains In Imo State. Michael Okpara University of Agriculture. Retrieved June 7, 2026, from http://repository.mouau.edu.ng/works/global-warming-potentials-and-degradation-rate-assessment-of-soils-of-selected-flood-plains-in-imo-state-7-2
MLA
AKANINYENE, MICHAEL, and OKON. "Global Warming Potentials And Degradation Rate Assessment Of Soils Of Selected Flood Plains In Imo State." Michael Okpara University of Agriculture, 10 Aug. 2023, http://repository.mouau.edu.ng/works/global-warming-potentials-and-degradation-rate-assessment-of-soils-of-selected-flood-plains-in-imo-state-7-2. Accessed June 7, 2026.
Chicago
AKANINYENE, MICHAEL, and OKON. "Global Warming Potentials And Degradation Rate Assessment Of Soils Of Selected Flood Plains In Imo State." Michael Okpara University of Agriculture (2023). Accessed June 7, 2026. http://repository.mouau.edu.ng/works/global-warming-potentials-and-degradation-rate-assessment-of-soils-of-selected-flood-plains-in-imo-state-7-2