Restoration of Juniperus excelsa Bieb. and Olea europaea L. subsp. africana

324 Pages·2015·20.12 MB·English

Restoration of Juniperus excelsa Bieb. and
Olea europaea L. subsp. africana (Mill.) p. S. Green
woodlands in Eritrea
A thesis presented for the degree of
Doctor of Philosophy
at the
University of Stirling
by
Philip Scott Jones, BSc, RGN, RMN
Department of Biological and Molecular Sciences
University of Stirling, FK9 4LA, Scotland
. /~
ii
ABS1RACT
The research aim was to assess the vegetation and soils of the Rora
/'
Habab plateau, Eritrea and to develop methods of propagating the native tree
species, juniper and olive. The research consisted of vegetation and soil
surveys, interviews with local people, archival research, and experiments on
propagation of olive and juniper. Junipers are now confined to the north of
the plateau. Olives are more abundant in the north but have very few
individuals in the centre, where there are many dead trees, or south. Soil
erosion was ubiquitous and often severe. Soil morphology and nutrient status
were related to vegetation, topography, land use, and erosion status, and
varied greatly over short distances. Soil texture was coarser and most chemical
factors (except total Ca and exchangeable Na) were lower in the south.
Organic C, total N, exchangeable Ca, percent day, CEC and the sum of bases
were higher in soils from grazed land than in cultivated fields. Germination of
olive seeds was 92% when the endocarp was removed; stratification had little
effect. Rooting of olive stem cuttings attained 76% under mist when parent
plants were fertilised and cuttings were treated with rooting hormone.
Germination for juniper was 56% after stratification at 5°C for 30 to 60 days.
Juniper stem cuttings rooted in only one of three experiments, where rooting
was 78% in a well ventilated, cool, low-mist environment. Olive seedlings
which were fertilised and watered every 7, 14, or 21 days for two months,
were taller, had lower root:shoot ratios and soil moisture than unfertilised
plants. Fertilised seedlings watered every 28 days died. Root volume was less
for plants watered every 21 days but watering interval had little effect on
other variables in unfertilised seedlings. Ecological restoration is urgently
required to rehabilitate the Rora plateau, which has Africa's most northerly
remnant juniper / olive woodlands.
III
CONTENTS
PAGE
Abstract. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ii
List of Tables. . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . .. viii
List of Figu.res. . . . . . . . . . . . . . . . . . . \ . . . . . . . . . . . . .. :xiii
List of Plates. . . . . . . . . . . . . . . . . 0. . .'. . . . . • . • . . . . . .. xv
Ackn.owledgements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xvi
Objectives and Introduction to Thesis.. . . . . . . . . . . . . . . . . . . xix
CHAPTERl
RESEARCH CONTEXT AND STUDy AREA
POLmCAL AND SOCIAL CONTEXT OF RESTORATION IN ERITREA
Description of Eritrea . 1
Political History 3
Social Effects of War and Drought 5
THE RORA HABAB STUDy AREA
Description of the Rora Habab Plateau 6
The Human History of Rora Habab 7
Evidence from Historical maps and Artefacts 9
Settlements 10
Recent Economic Deyelopment on Rora Habab 12
CHAPTER 2
PHYSICAL GEOGRAPHY AND AGRICULTURE IN ERITREA AND ON 1HE
RORA HABAB PLATEAU
GEOLOGY AND CLIMATE
Eritrea 14
Geology 14
Climate 16
Rora Habab Study Site 19
~
Geology 19
Climate 21
lV
PAGE
Chapter 2, cont'd.
VEGETATION OF RORA HABAB
Phyto~ography 23
Major oody Species and their Uses 24
AGRICULTURAL SYSTEMS AND LAND TENURE
Agricultural Systems in Eritrea 35
Pastoralism 36
The Seed-Farming Complex 37
The Highland Grain-Plough Complex 38
Land Tenure in Eritrea 39
Diesa 39
Risti 40
. Agriculture on the Rora Habab Plateau 41
Crops 41
Livestock 45
CHAPTER 3
VEGETATION SURVEY
INTRODUCTION AND OBJECTIVES 48
METHODS
49
49
51
52
53
General Characteristics of Transects and Plots 61
Vegetation 65
Species Distribution and Density 67
Trees
Density . 67
Cover, basal area and height, by plot 73
Cover, basal area and height, by species 74
Smaller Plants 78
Tree Cores from Junipers at three'Sites 82
DISCUSSION 85
v
PAGE
CHAPTER 4
SOIL SURVEY
INTRODUCTION AND OBJECTIVES 89
METHODS
Survey Desirn and Field Methods 90
Laboratory nalyses 92
RESULTS
Soil Formation 94
Climate 95
Biota 96
Relief 97
Parent Material 98
Time 98
99
C~=~nd
Soil Physical Properties . 100
Overview of Properties and Correlations among them 100
Surface Horizon Properties by Site 111
Surface Horizon Properties by Land use Class 122
Soil Classification and Mapping 125
Soil Mana§ement Practices 130
Loca Soil Classification and Land use Considerations 130
Soil and Water Conservation 134
DISCUSSION 137
CHAPTERS
PROPAGATION OF OLIVE AND JUNIPER
INTRODUCTION 140
FACTORS AFFECTING THE GERMINATION OF OLEA EUROPAEA
SUBSP. AFRICANA
Introduction 143
Methods
Seeds 144
Experimental Design an4· Treatments 145
Statistical Analysis 149
Results
Seed Length and Weight 151
Hypotheses 1 to 6 .. 151
Discussion - 161
Conclusion 164
VI
PAGE
Chapter 5, cont'd.
VEGETATIVE PROPAGATION OF OLEA EUROPAEA
SUBSP. AFRICANA
Introduction 166
Methods
Experimental Design
Experiment 1 168
Experiment 2 169
Statistica1 Analysis
Experiment 1 172
Experiment 2 173
Results
Experiment 1 174
Experiment 2 176
Discussion 182
Conclusion 187
FACTORS AFFECTING THE GERMINATION OF JUNIPERUS EXCELSA
Introduction 188
Methods
Seeds 189
Experimental Design and Treatments 190
Germination Conditions 190
Statistical Analysis 192
Results 193
Discussion .
Experimental Observations 196
Comparison with other Studies 198
Conclusion .' 200
VEGETATIVE PROPAGATION OF JUNIPERUS EXCELSA
Introduction 201
Methods
Experimental Design 202
Experiment 1 203
Experiment 2 204
Statisticcil Analysis 204
Results 206
Discussion 208
Vll
PAGE
CHAPTER 6
INFLUENCE OF FERTILISATION AND DROUGHT STRESS
ON OLEA EUROPAEA SUBSP. AFRICANA SEEDLINGS
INTRODUCTION 210
METHODS 212
Measurement of Shoot and Root Volume 215
Statistical Analysis 217
Multiple Comparisons and MANOVA 218
RESULTS 219
DISCUSSION 226
CONCLUSION 227
CHAPTER 7
CONCLUSIONS AND RECOMMENDATIONS
SUMMARY OF CHAPTERS 1 TO 6 229
IMPLICATIONS FOR RESTORATION 230
Is Restoration Feasible? 230
What are we Restoring? . . . 234
Extracts from "Escursione aIle Rore degli Habab ed
all'a1ti~ano eli Nacfa" Emanuele Naldini, 1916 235
Where do we go om here? 239
Plates 241
References 250
. Appendix to chapter 2 262
Ap pendix to chapter 3 264
Ap pendix to chapter 4 soil profile descriptions, Bada 265
soil profile deSCriptions, Berige 279
soil profile descriptions, Laba 292
viii
List of Tables
PAGE
Table 2.1. N ames and local uses of the seven commonest tree
and shrub species on the Rora Habab plateau, Eritrea,
including the principal synonyms and common
English names. 25
Table 2.2. Cultivable land and l1~ulation in 1985 in Bacla (north),
Berige (central), and a a (south) villages on Rora
Habab plateau, Eritrea. 43
Table 2.3. Yields of wheat, barley and ~otatoes in 1988 from
three areas of Rora Habab, ritrea. . 43
Table 2.4 Estimated livestock numbers in 1984, for the thirteen
villages on the Rora Habab plateau, Eritrea, and for
the villages of Bacla, Berige and Laba. . 46
Table 3.1 Major characteristics of plots along three transects on
Rora Habab plateau, Eritrea. 56-58
Table 3.2 Numbers of living Juniperus excelsa, Olea eurofiaea
subsp. africana, and Rtius abyssinica trees and iving
stum~s in the plots where they occurred on Rora
Haba plateau, Eritrea. 60
Table 3.3 Numbers of flats according to average hillslope, major
land use, an erosion categories for thirty-nine plots on
Rora Habab plateau, Eritrea. 64
Table 3.4 Field observations on the condition of Juniperus excels a
and Olea europaea subsp. africana trees from Rora
Habab plateau, Eritrea. 66
Table 3.5 NumberQ~er hectare of living and dead Ju~s
excelsa, ea europaea subs~. africana and
abyssinica trees ~10 cm at 1. m hifih, and numbers
of seedlings <50 cm and ~50 cm ta alo~ three
transects and at Shamotet on the Rora abab
plateau, Eritrea. 69
Table 3.6. Percent cover and basal area, by plot, of Juniperus
excelsa, Olea europaea subsp. afncana and ~
abyssinica trees alona, north, central and south
transects on Rora Ha ab, Eritrea. ., 71
Table 3.7 Numbers of trees, mean canopy cover, mean basal
area and mean height for indIviduals of Juniperus
excelsa and Olea europaea subsp. africana in the
twenty-five plots with living trees on Rora Habab
plateau, Eritrea. 72
Table 3.8 Numbers of trees, mean canopy cover, mean basal
area and mean hei~t for individuals of Rhus abyssinica
in the six plots wit living trees on Rora Habab
plateau, Eritrea. 79
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PAGE
Table 3.9 Percent cover of shrubs and herbs along north, central
and south transects and at Shamotet on the Rora Habab
plateau, Eritrea. 80
/"
Table 4.1 Matrix of positive and negative correlations amon~
selected A horizon soil properties from 39 soil pro iles
on Rora Habab plateau, Eritrea. 101
Table 4.2 Means, standard deviations, maximum and minimum
values of 20 surface soil properties from Rora Habab,
Eritrea. 103
Table 4.3 Major characteristics of surface soil horizons in 39 plots
along three transects in the (a) northern, (b) central, and
(c) southern zones on the Rora Habab plateau, Eritrea. 105-107
Table 4.4 Values for seven soillroperties from samples taken
at 10 cm intervals at erige plot no. 10, Rora Habab,
Eritrea. 110
Table 4.5. Electrical conductivity, soluble salts, sodium adsorption
ratio, percent base saturation, exchangeable sodium
&ercentage, and pH of 8 surface and 2 subsurface soils
om three transects on Rora Habab, Eritrea. 116
Table 4.6 Differences between surface soil properties from ~azed
land and fields along three transects on the Rora abab
plateau, Eritrea. . 123
Table 4.7 (a) Moist and d~ colour of surface horizons from
selected soil pro· es from Rora Habab, Eritrea, used
for comparison with other soil properties.
(b) Significant results from one-way analyses of variance
of 15 surface soil fJroperties with soil colour as the
dependent varia Ie. 131
Table 5.1 Maternal plant fe0up, endocarp, and stratification
treatments on 0 a europaea subsp. africana seeds
from Eritrea. 146
Table 5.2 Length of seeds with endocarp, and weight of seeds
wittl and without endocarp from four maternal plant
groups of Olea europaea subsp. africana. 152
Table 5.3. Increase in weight after imbibition of Olea europaea
subsp. africana seeds from three maternal plants
from Eritrea. 153
Table 5.4 Percent germination of Olea europaea subsp. africana
seeds from Eritrea by length of stratification at
different temperatures, with endocarp intact, removed,
or cracked. 153
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PAGE
Table 5.5 Percent germination of Olea europaea subsp. africana
seeds from Eritrea by length of stratification at
different temperatures, with endocarp intact
or removed. // 154
Table 5.6 Percent germination of Olea europaea subsp. africana
seeds from Eritrea stratified for 14 or 28 days at 15°C,
with endocarp removed or cracked. 154
Table 5.7 Percent germination of Olea euro~aea subsp. africana
7
seeds from Eritrea collected in 19 and 1988, stratified
at 15°C for 14 or 28 days, with endocarp removed
or intact. . 155
Table 5.8 Percent germination of Olea europaea subsp. africana
seeds from Eritrea by length of stratification at different
temperatures, with endocarp removed. 155
Table 5.9 Percent germination of Olea europaea subsp. africana
seeds from Eritrea by length of stratification at different
temperatures, with endocarp removed. 156
Table 5.10 Percent germination of Olea europaea subsp. africana
seeds from Eritrea by length of stratification at different
temperatures, with endocarp intact. 156
Table 5.11 Results of ANOVAs for six hypotheses concernina
~ermination of Olea europaea subsp. africana see s
om Eritrea. . 157
Table 5.12 Results of contrasts for hypotheses 4 and 6, concerning
~ermination of Olea europaea subsp. africana seeds
om Eritrea. . 158
Table 5.13 Number of cuttings taken by watering and fertiliser
regimen (10 cuttings her combination) from each of
three O. eurooaea su sp. africana parent groups for
experiment (t). 170
Table 5.14 Numbers of O. eucr~ aea subS~. africana cuttings which
rooted or formed us after 0 d, according to parent
plant, application of rooting hormone, and. type of
cutting. . ' 170
Table 5.15 Numbers of O. europaea subsp. africana cuttings which
produced new leaves after 90 d, according to parent
plant,application of rooting hormone, ana type of
cutting. . 175
Table 5.16 Numbers of O. europaea subsp. africana cuttings which
rooted and formed new leaves after 90 d. 175