ABSTRACT
A detailed soil survey of 1.8ha forest pedosite at Michael Okpara University of Agriculture, Umudike (MOUAU), Umuahia, Abia State, Nigeria, was conducted to evaluate land capability, degradation status and pedodiversity of the site. Rigid grid method of soil survey was adopted at a scale of 1: 10 000. Datas obtained were analyzed using descriptive statistics. The soil samples were carried to the laboratory to analysis its physical and chemical properties. Three profile pits were dug measuring 1m x 2m, its depth ranged 0.40 -1.50 m Results showed that two soil mapping units FPMOUAUI and FPMOUAU II were identified. Mapping unit FPMOUAU I (0.25ha) is well drained, shallow (≤ 50 cm deep), gravelly and is located on an elevation ranging from 103 – 108 m above sea level. Mapping unit FPMOUAU II (1.55ha)is deep (> 100 cm deep), imperfectly drained, and found on a lower landscape (≤ 103 m above sea level) to mapping unit FPMOUAU I. Using silt-clay ratio as an index of degradation, the soils are degraded ranging from 0.17 – 0 5 and 0.12 – 1 8 for mapping units FPMOUAU I and FPMOUAU II, respectively. At the epipedon, the soils are strongly to moderately acid (pH{H20}4.9 – 5.8), medium to high in organic matter (2.27 – 5.8 %), low to high in total N (0.07 – 0.34 %), low to high in available P (14 – 29 mg/kg) and medium in exchangeable K (0.24 – 0.33 cmol/ kg). The soils are classified as Lithic Udorthents (USDA); Eutric Loamic Regosols (WRB) for mapping unit FPMOUAU I and Typic Paleudalfs (USDA); Stagnic Loamic Luvisols (WRB) for mapping unit FPMOUAU II. The pedosite is arable land belongs to Land Capability Class II. However, land capability unit for mapping unit FPMOUAU I is Class IIs based on shallowness of the soils and Class IIw for mapping unit FPMOUAU II due to imperfect drainage. The Shannon entropy was 0.65 and evenness was 0.69, while the Simpson’s dominance index was 0.05 indicating that the soils are not homogeneous. I recommend that the need to apply soil conservation measures such as construction of an embankment at the upper part of the forest pedosite to reduce run off into the pedosite causing its degradation beyond expectation. The land capability classification has generated data to assist in the choice of appropriate trees (shallow – rooted and deep - rooted) for afforestation programme. The heterogeneity of the site as further revealed by the pedodiversity is a vital soil information to aid in the management of the forests.
TABLE OF CONTENTS
Title Page i
Declaration ii
Certification iii
Dedication iv
Acknowledgements v
Table of Contents vi
List of Tables x
Lists of Figures xi
List of Plates xii
Abstract xiii
CHAPTER
1: INTRODUCTION 1
1.1 Background
of the Study 1
1.2 Statement
of the Problem 3
1.3 Justification of
the Study 4
1.4 Objectives of Study 4
CHAPTER 2: LITERATURE REVIEW 5
2.1 Land
Capability Classification 5
2.1.1 Modification of land capability
classification 7
2.1.2 Criteria
for placing soils in capability classes 8
2.
2 Land Capability Studies in Ikwuano
Local Government Area (LGA) 8
2.3 The Concept of Pedodiversity 10
2.3.1 Measurement
of pedodiversity 14
2.3.1.1 Shannon’s entropy or
diversity index (H) 14
2.3.1.2 Maximum diversity 15
2.3.1.3 Evenness (E) 15
2.3.1.4 Simpson’s dominance index (Gini index) (D) 16
2.3.1.5 Gini-Simpson’s diversity index (G) 16
2.3.2 Importance
of pedodiversity 16
2.4 Pedosites 17
2.4.1 Forest
Pedosite 17
2.4.1.1 Criteria used to evaluate forest soils as a pedosite 17
2.5 Forests 18
2.5.1 Importance
and benefits of forests in an environment 19
2.5.2 Major Forest Hazards 19
2.5.3 Tropical forest vegetation characteristics 20
2.6 Forest Soils 20
2.6.1 Forest
soils and agricultural soils 21
2.6.2 Characteristics
of forest soils 21
2.6.2.1 Morphological
and physical properties of tropical forest soils 21
2.6.2.2 Chemical properties of tropical forest soils 22
2.7 Degradation
of Tropical Soils 23
CHAPTER
3: MATERIALS AND METHODS 25
3.1 Description of the Study Area 25
3.1.1 Location 25
3.1.2 Climate 25
3.1.3 Vegetation 27
3.1.4 Geology, geomorphology and parent material 27
3.2 Field Method 28
3.2.1 Detailed Soil Study 28
3.3 Laboratory
Analyses 31
3.3.1 Soil
sample preparation 31
3.3.2 Physical
analyses 31
3.3.2.1 Particle size distribution 31
3.3.2.2 Gravimetric moisture content 32
3.3.2.3 Saturated hydraulic conductivity 33
3.3.2.4 Bulk density determination (⍴b) 34
3.3.2.5 Total porosity (Pt) 34
3.3.2.7 Micro
porosity (Pmi)
34
3.3.3 Chemical analyses 35
3.3.3.1 Soil pH 35
3.3.3.2
Exchangeable acidity (hydrogen (H+) and aluminium (Al3+) 35
3.3.3.3 Total Exchangeable Bases (TEB) 35
3.3.3.4 Percentage Base Saturation (BS) 35
3.3.3.5 The Effective Cation Exchange Capacity (ECEC) 36
3.3.3.6 Organic carbon 36
3.3.3.7 Total nitrogen 36
3.3.3.8 Available phosphorus 37
3.4 Land
Evaluation Method 37
3.4.1 Land Capability Classification 37
3.5 Degradation of the Forest Pedosite 39
3.6 Statistical
Analysis 41
3.7 Soil Classification 41
3.8 Pedodiversity 41
3.8.1 Shannon’s entropy or diversity index (H) 41
3.8.2 Maximum
diversity (Hmax) 42
3.8.3 Evenness
(E) 42
3.8.4 Simpson’s
dominance index (D) 43
3.8.5 Gini-Simpson’s diversity Index (G) 43
CHAPTER
4: RESULTS AND DISCUSSION 45
4.1 Soil Mapping Units 45
4.1.1 Morphological
properties of the soil mapping units 45
4.1.2 Physical properties
of the soil mapping units 49
4.1.3 Chemical
properties of forest
pedosite 54
4.1.4 Degradation
status of the soils 60
4.1.5 Soil classification of
FOPED I 62
4.1.6 Soil
Classification of FOPED II 64
4.2 Land Capability Classification 65
4.3 Pedodiversity
of the Forest Pedosite 67
CHAPTER 5: SUMMARY,
CONCLUSION AND RECOMMENDATIONS 69
5.1 Summary 69
5.2 Conclusion 70
5.3 Recommendations 70
References
Appendix
LIST OF TABLES
PAGE
3.1: Land Capability Classification
System-General guidelines 38
3.2 Rating
of Soil Degradation Based on Silt: Clay Ratio 40
3.3: Interpretation
of Pedodiversity Ratings 44
4.1: Morphological
Properties of the Forest Pedosite 48
4.2: Physical Properties
of the Soils 50
4.3: Summary of the Physical Properties of the Forest
Pedosite at 0 – 30 cm 51
4.4: Chemical properties
of the Forest Pedosite 55
4.5: Statistical
Summary of Chemical Properties Forest Pedosite at 0 – 30 cm Depth 56
4.6: Degradation
Status of the Forest Pedosite 61
4.7: Soil Classification of the Forest Pedosite 63
4.8: Pedodiversity indices of the Forest
Pedosite 68
LIST FIGURES
PAGE
2.1: Pedodiversity: reasons for preservation of a
pedological heritage 11
2.2:
Relationships
between pedodiversity, biodiversity, landform diversity,
lithodiversity, climate diversity, hydrodiversity and
land use diversity 12
3.1: Map of
the Study Area 26
3.2:
Schematic diagram showing auger soil
sampling points (Points X=
Grid points where auger samples were taken) 30
4.1:
Land Capability Map 66
LIST OF PLATES
PAGE
A: Shallow
soil of Pedon 1 85
B: Pedon
3 with its distinct horizon 88
CHAPTER
1
INTRODUCTION
1.1 BACKGROUND
OF THE STUDY
A land capability classification
produced from a detailed soil survey is a vital tool to help land users to make
meaningful decisions about the use of their land to optimize returns and avoid environmental
degradation. Land capability classification is a broad grouping of soils based
on their limitations as a guide to assess suitability of the land for arable
crops, grazing and forestry (Dent and Young, 1981). Consequently, it is one of
the ways to interpret soil survey data correctly in order to guarantee good
land use planning. Against this background, Akamigbo (1999) advised that
Nigeria should evolve a land use policy for the 21st century using
land capability classification as a tool. Land use policy involves a body of
laws whether legislative, executive, administrative directives and specific
commitments of government to enhance rural life and reduce poverty through
sustainability in agriculture and maintenance of environmental harmony, among
others. It aids judicious application of inputs to achieve sustainable soil
management decisions, to enhance agro - technology transfer, and overall
agricultural development. . Consequently, it is a sustainable land management
strategy because the system of land capability classification requires
that every hectare of land be used in accordance with its capability and
limitations. It is designed to emphasize the hazards in different kinds of
soils. It is a general soil interpretation based primarily on physical factors
of soil, site, climate, for general agriculture. Jenny (1941)
Land degradation is a
growing problem in many countries. Land degradation implies loss or impairment
of soil, water or productivity potential. According to Adegeye and Omonona (1999)
and Chukwu et al. (2012) land
degradation involves the decline in productivity as a result of the
impoverishment and depletion of vegetative cover, exposure of the soil to wind
and water erosion, reduction of soil organic matter and nutrient content, and
deterioration of soil structure and its capacity to retain water. The authors
identified soil erosion as the rampant forms of land degradation in Nigeria.
Sheet erosion is most serious in Nigeria and it is normally a natural slow
process which occurs on a land which is not dead flat, which has a soil cover
and which receives rainfall high enough to produce run-off (Adegeye and
Omonona, 1999). Chukwu et al. (2012)
in a land capability classification of Ikwuano LGA, Abia State, included
Umudike within which the forest pedosite falls, under land capability unit
class IIen, where low nutrient reserve and soil (sheet) erosion are major
limitations to productivity.
Pedodiversity is credited to Alex McBratney who coined the terminology in
1992. The word ‘pedodiversity’ is a combination of both the Greek word ‘pedo’
and English word ‘diversity’. While ‘pedo’ means soils (Buol et al., 1997), diversity means the state
or fact of being diverse, different, variety or multi-formity (Gaston,
2000).The concept of diversity has been widely used in ecological studies,
although mainly for the biotic component. Pedodiversity is a way of measuring
soil variation (McBratney, 1992)
usually using taxa from well-accepted international soil classification
systems (Ibáñez et al., 1995; Guo et al., 2003; Phillips and Marion, 2005). It is a quantitative expression of the
patterns of soil distribution, the soil type, and its extent in an area
(Florea, 1998). Notwithstanding, the
difficulties of concepts of individuals and species for soil, soil scientists
have pragmatically adapted the concept of biodiversity and used species
richness, abundance, and Shannon's index as indices for measuring it.
The term forest is defined by the Forestry Commission (2011) as a land
largely covered with trees (defined as land under stands of trees with a canopy
cover of at least 20%), whether in large tracts (generally called forests) or
smaller areas known by a variety of terms including woods, copses, spinneys or
shelterbelts. Forest sites house numerous ancient monuments and other cultural
and historical remains (Svensson, 2005) as their soils are a repository of
environment and cultural information. Costantini (1999) defined pedosite as a
geo-referenced soil or site (forest) having cultural heritage, that is, a soil
exposure or a soil-scape where an extraordinary cultural interest has been
recognized.
1.2 STATEMENT OF THE PROBLEMS
Persistent food insecurity and
failure of agriculture to supply adequate quantities of raw materials to
industries are common issues in developing economies. This is attributed to
many factors, among which is soil resource illiteracy. The OFAR (1984, 1985)
identified poor knowledge of soil as a major problem hindering agricultural
development in Umuahia Agricultural Zone. This is not a surprise as similar
observations have been made in most parts of Nigeria and Africa. Chukwu et al. (2013) Some of the reasons for
this situation are related to lack of soil survey reports of most rural
communities and Local Government Areas (LGAs) where food and fiber production
take place. Also, the scales of most national soil surveys are at
reconnaissance level such that pedological information about rural communities
is virtually non-existent.
Available information has shown that the land capability
of the soil-scape where the forest reserve in the university is located is not
known. Consequently, there is a dearth of information about the limitations or
hazards inherent in the site and opportunities for alternative land use options
the site can be put. This information is necessary for land use planning
especially in the university environment. Pedodiversity studies are novel in
Nigeria, especially in the south-eastern agro-ecological zone. As a
quantitative expression of the patterns of soil distribution and its extent in
an area, there is paucity of information on the forest pedosite (reserve) at
the Michael Okpara University of Agriculture, (MOUA), Umudike. Baseline data of
the forest pedosite are necessary to explain the diversity of the naturally
occurring tree species in the forest as it will aid forest management
especially afforestation programmes.
1.3 JUSTIFICATION OF THE STUDY
Land capability
classification can give an insight into the reasons behind the dominance of
tree species in the forest pedosite. The study will ascertain, for the first
time, the distribution of soil individuals in the forest. Since there is a
dearth of information on land capability classification and pedodiversity of
this forest pedosite, it becomes expedient, at this time, to undertake a study
of for the purpose of enhancing soil information system about the area. From
the foregoing it makes the study necessary and justified.
1.4 OBJECTIVES OF STUDY
The main objective of this study was to assess the land capability
asses state of degradation and pedodiversity of the forest pedosite at MOUA,
Umudike. The specific objectives are;
i. delineate
soils of the forest pedosite at MOUA,Umudike
ii. characterize
and classify the soils of the forest pedosite.
iii. provide
land capability classification of the forest pedosite.
iv. ascertain
the pedodiversity of soils in the pedosite.
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