Bangor University DOCTOR of PHILOSOPHY
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Bangor University DOCTOR OF PHILOSOPHY Management of Vitellaria paradoxa in Guinea savanna rangelands in Ghana. Amaning, E.Osei- Award date: 1996 Link to publication General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights. • Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal ? Take down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. Download date: 09. Oct. 2021 MANAGEMENT OF VITELLARIA PARADOXA IN GUINEA SAVANNA RANGELANDS IN GHANA BY E. OSEI-AMANING BSc. (Agriculture)(Kumasi) rW DDEFNYDDIO yN LLYFBC7ELL YN UNIC BE CONSULITED U; THE LIBRARY ONLY A thesis submitted in partial fulfillment for the requirementsfor the PhilosophiaeDoctor in the University of Wales Departmentof Forestry and Wood Science School of Agriculture and Forest Sciences University of Wales, Bangor January, 1996 -J Abstract From 1993-1994, a study of Vitellaria paradoxa was carried out. This study involved an in-depth review of biological and ecological information on Vitellatia throughout its range. Stand studies and an analysis of the climate in relation to fire risk. There were also experimental investigations of germination and pollination. All field studies were at the site of the Cocoa Research Institute outstation at Bole. Stand characteristics of Vitellaria (>10 cm dbh) at the 68 kM2 plot of the Cocoa Research Institute's Sheanut Research Station, Bole were examined in two strata distinguished on the basis of distance from the nearest village: >3.0 km and <3.0 km. Regeneration (<10 cm dbh) was assessed and recorded for height, root collar diameter and mode of regeneration. Analysis of variance indicated higher stocking of individuals > 10 cm dbh further from villages but significantly more Vitellaria trees >10 m tall close to villages. Suckers accounted for > 86% of regenerating individuals, and more than 90% of regenerating plants were < 50 cm high. Analysis of climatic data indicated a mean drought index (1990-1994) of 514 ± 61 points. However, the fire danger index never reached an extreme value. The germination response of depulped, cracked and intact seeds of Vitellaria sown under- and outside the canopy of mature Vitellatia trees (> 30 cm dbh), showed a significant association between germination and seed treatment: a higher proportion of depulped than intact seeds germinated. Open pollinated flowers, gave significantly lower fruit set than hand-pollinated flowers. There was no difference, however, in the amount of fruit set achieved with pollen from sources 50 m, 500 m and 1000 m away or from flowers of two different style lengths. It is concluded that fires are adversely affecting the population structure and natural regeneration of stands at Bole, and that low fruit set in Vitellaria is due at least in part, to low vector activity. Suggestions are made for future research on the species. TABLE OF CONTENTS Title page Abstract Table of contents List of tables v List of figures ix List of plates x List of appendices x Acknowledgements xii Declaration xii 1.0 Introduction 1 2.0 Literature review 6 2.1 Taxonomy and systematics of the species 6 2.1.1 Description 7 Seedling 7 Mature tree 8 Habit, size and form.. 8 Foliage 10 Inflorescence and flowers 11 Fruits and nuts 13 2.2 Biology 15 2.1.1 Chromosome number 15 2.2.2 Life cycle and phenology 15 Life cycle 15 Phenology 17 2.2.3 Reproductive biology 22 Pollination 22 Breeding system 23 Seed dispersal 24 Germination 25 2.2.4 Physiological studies 25 2.2.5 Susceptibility to diseases 26 2.3 Ecology 28 2.3.1 Geographical distribution 28 Present distribution 28 Range 30 2.3.2 Environmental factors in distribution 30 Elevation 30 Climate 32 Rainfall 33 Temperature 33 Catenas and toposequences 36 Site 39 2.3.3 Vitellaria as a vegetation component 42 Population levels 42 Representation 46 Relations with natural fauna 47 Relations with man-including fire 50 Vegetation types 51 Associated species 54 Associated plant vascular parasites 61 3.0 Study site, materials and procedures 62 3.1 Study site 62 3.2 Derivation of drought and fire risk indices 64 3.2.1 Drought index 64 3.2.2 Fire danger index 65 3.3 Population and natural regeneration studies 65 3.3.1 Population structure of Vitellaria at Bole 65 3.3.2 Regeneration sampling 68 3.4 Germination and seedling survival in Vitellaria 69 3.4.1 Seed treatment and canopy influence on germination in Vitellaria.. 69 3.5 Flowering and pollination studies.. 72 3.5.1 Studies on flower development and floral dimorphism 72 3.5.2 Fruit production and abscission in Vitellaria in relation to tree size and pollen source distance.. 73 3.5.3 Source and style length of pollen donor on fruit production in Vitellaria 76 3.6 Data handling and statistical analyses 80 4.0 Results 82 4.1 Drought and fire danger indices 82 4.1.1 Drought indices 82 4.1.2 Fire danger indices 85 4.2 The Vitellaria population at Bole 89 4.2.1 Individuals ý10 cm dbh 89 4.2.3 Natural regeneration of Vitellaria 93 4.3 Germination and seedling survival 101 4.3.1 Seed treatment and canopy influence on germination 101 4.4 Flowering and pollination studies.. 105 4.4.1 Studies on flower development and floral dimorphism 105 4.4.3 Effect of tree size and pollen source on fruit production and abscission in Vitellalia 108 4.4.4 Effect of source and style length of pollen donor on fruit production and abscission 114 5.0 Discussion 120 6.0 Conclusions and recommendations 139 References 145 IV List of Tables Table 2.1 Leaf size reported for Vitellaria paradoxa 11 Table 2.2 Measurement of parts of flowers of Vitellaria 13 Table 2.3 The size/weight of fruit reported for Vitellaria 14 Table 2.4 Reported chromosome number for Vitellaria 15 Table 2.5 Vitellaria: seedling growth and increment 16 Table 2.6 Reports on relationship between age and maturity in Vitellaria in natural communities 17 Table 2.7 Time of presence of ripe fruits for Vitellaria in its range 22 Table 2.8 Dispersal animals reported for Vitellaria.. 26 Table 2.9 Altitude of occurrence of Vitellaria 32 Table 2.10 Distribution of Vitellaria in relation to major soil groups 41 Table 2.11 Estimatesof stocking of Vitellariain natural communities.. 43 Table 2.12 Arthropods associatedwith Vitellariain natural vegetation 49 Table 2.13 Designationsused for vegetation within which Vitellariais a typical constituent 52 Table 2.14 Erect woody species associatedwith subsp. paradoxa in natural communities 57 Table 2.15 Erect woody species associatedwith subsp. nilotica in natural communities 59 Table 2.16 Vascular plant parasites associatedwith Vitellatia 61 Table 4.1 McArthur Forest Fire Danger Meter fire index categories 85 Table 4.2 Numbersenumerated by size class and by stand of Vitellaria,Parkia and other tree species at Bole 88 Table 4.3 Basal area and stand density of trees >10 cm dbh determinedby direct and by Ward's method for the stands at Bole 89 Table 4.4 Analysis of variance: stocking of Vitellariaby height class and stratum at Bole 92 Table 4.5 Mean stocking of Vitellariaby height class and stratum at Bole, Ghana 92 Table 4.6 The percentageof each stand sampled for seedlings.. 93 V Table 4.7 Summary by height class, assessment year and mode of regeneration, of regeneration at Bole 95 Table 4.8 Summary by root collar diameter class, assessment year and mode of regeneration, of regeneration at Bole 96 Table 4.9 Summary of stocking per hectare of regeneration in areas <3 km and >3 km from villages and by year of assessment at Bole 97 Table 4.10 Analysis of variance: stocking of regeneration in areas <3 km and >3 km from villages in 1993 and 1994 at Bole. 97 Table 4.11 Summary of stocking per hectare of saplings in areas <3 km and >3km from villages and assessment year at Bole 98 Table 4.12 Analysis of variance: stocking of natural regeneration saplings assessed in areas <3 km and >3 km from Villages at Bole.. 99 Table 4.13 Effect of seed pre-treatment and canopy influence on seed germination at Bole 101 Table 4.14 Effect of seed pre-treatment and canopy influence on seed germination at Bole 102 Table 4.15 Mean seedling height of Vitellaria at 20 weeks outside and under canopy of mature trees in relation to seed pre-treatment at Bole 103 Table 4.16 Analysis of variance: effect of seed pre-treatment and canopy situation on seedling height at 20 weeks at Bole 103 Table 4.17 Mean root collar diameter of Vitellaria at 20 weeks outside and under canopy of mature trees in relation to seed pre-treatment at Bole, Ghana 104 Table 4.18 Analysis of variance: effect of seed pre-treatment and canopy situation on root collar at 20 weeks at Bole 104 Table 4.19 Frequency distribution of style length in five Vitellaria populations at Bole 105 Table 4.20 The relationship between tree size and flower development in Vitellaria at Bole 107 vi Table 4.21 Influence of pollen source and tree size on the percentage of fruit set in Vitellaria 4 weeks after hand-pollination at Bole 108 Table 4.22 Analysis of variance: source of pollen and tree size on fruit set in