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International Journal of Innovative Research and Advanced Studies (IJIRAS)
Volume 5 Issue 8, August 2018
ISSN: 2394-4404
Propagation And Regeneration Of Important Indigenous Tree
Species In Kakamega Forest, Kenya
Carolyne Busuru
MSc student, Department of Natural Resources, Egerton
University, Kenya
Gilbert. O. Obwoyere
Dr.rer.nat, Lecturer, Department of Natural Resources,
Egerton University, Kenya
Bernard Kirui
PhD, Lecturer, Department of Natural Resources, Egerton
University, Kenya
I. INTRODUCTION
A. BACKGROUND INFORMATION
The study was done within the spatial dimensions of
Isecheno forest station of kakamega south forest where P.
africana, O. capensis and C. megalocarpus is abundant. This
study evaluated regeneration potential of the African cherry,
identified the appropriate stage of collecting seeds for
propagation and suitable sowing media that gives optimum
germination and sought to identify other tree species with
potential commercial uses which could be used as alternative
to P. africana and hence ease the exploitation pressure that it
currently faces due to its medicinal value and valuable
multipurpose timber. Therefore, experiments were set for P.
africana vis avis O. capensis and C. megalocarpus. However,
it should be noted that O. capensis did need seed in Kakamega
forest during the year of study and therefore posed a challenge
in the experiments that involved mature ripe and mature green
seeds for propagation. Studies indicate that this species does
not seed regularly, (Orwa et al, 2009) observed that flowering
of this species takes place only at irregular intervals of up to
seven years in the late dry season. Only mean germination
percent of the seedlings in the different media was studied and
therefore, the study did not involve transplanting of the
seedlings.
B. PRUNUS AFRICANA ECOLOGY AND BIOLOGY
The African cherry (Prunus africana) belongs to the
subfamily Prunoideae of the Rosaceae family, it attains
highest diversity in temperate regions (Clemente et al, 2006).
Abstract: This study evaluated regeneration potential of P. africana vis a vis Olea capensis and Croton megalocarpus,
identified the seed for propagation and suitable sowing media that gives optimum germination results. An experiment was
set to evaluate these. Seeds were collected prepared, germinated under the different media types and germination percent
monitored. The data was collected on mean germination percent in different media ratio and statistical analyses
conducted. The results indicated that There was significant difference in the timing of the collection of seeds (F 2, 60,
f=24.47, P<0.001). Germination rate was significantly lower in stored seeds compared to the other two seed collection
stages i.e. mature green seeds and mature ripe. There was a significant ‘medium’ effect on the germination of C.
megalocarpus (F6,62, f=4.84, p<0.001), Prunus africana (Chi- square test = 14.10, d. f= 6, p = 0.029) and O. capensis (Chi
–square test = 18.33, d. f= 6, p = 0.005). From the results, it was concluded that the best seed for propagation of P.
africana is seed freshly harvested, mature and ripe even without any pre-treatment. It is therefore recommended that P.
africana seed should be sown in sand: sawdust 1:1 immediately after harvesting for optimum germination.
Keywords: Germination, Media, Propagation, Regeneration, Seeds.
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International Journal of Innovative Research and Advanced Studies (IJIRAS)
Volume 5 Issue 8, August 2018
ISSN: 2394-4404
It is an evergreen hardwood tree with dark-brown longitudinal
fissured bark and simple, thick, leathery, oval, leaves with
pointed ends. It grows at 700-3000 m above sea level, up to a
height of 40 m. It has creamy white flowers and produces
black fleshy fruits resembling a cherry when ripe, which are
eaten and dispersed by monkeys, birds and squirrels.
Flowering occurs between November and February although
sporadic flowering all over the year may be found in
Kakamega Forest of Kenya (Orwa et al, 2009). The unit for
sowing is the depulped fruit (the stone). The seeds are
desiccation sensitive (recalcitrant) and therefore only short-
term storage is recommended in damp sawdust in a cool dry
environment (Luke et al, 2013).
In nature, a fruiting tree can produce thousands of
seedlings (wildings) that can be collected and transplanted.
However, it is often seen that the wildings do not transplant
well. This therefore indicates the difficulty in propagation. In
terms of natural regeneration, this species shows low or
sporadic recruitment (Ewusi et al, 1992, Luke et al, 2013).
C. OLEA CAPENSIS ECOLOGY AND BIOLOGY
Olea capensis is often a bushy shrub or a small to medium
sized tree up to 10 m in height, but it may be much larger,
occasionally reaching 40 m; occurring in bush, littoral scrub
and evergreen forest. The fruits take about 6 months to ripen
(Tsingalia and Nyongesa, 2010). Seed storage behavior
appears to be orthodox (Albrecht, 1993). Growth is reported
fast in young plants but much slower in older ones. It is a
shade-tolerant, pioneer species and a dominant forest tree
(Orwa et al, 2009).
D. CROTON MEGALOCARPUS ECOLOGY AND
BIOLOGY
Croton megalocarpus is a hardy and fast-growing tree that
grows to 15-35 m with a distinctive layering of branches and a
rather flat crown. It is a pioneer species and it is found
growing in cleared parts of natural forests, forest margins or as
a canopy tree (Kiama and Kiyiapi, 2001). The species
regenerates well through seedlings, and under favorable
climatic conditions may sometimes become invasive (Maroyi,
2010). The seeds are extracted from the shell by cracking with
a hammer or a stone. On average there are 1700 seeds/kg.
II. RESEARCH OBJECTIVE
To document the regeneration potentials of P. africana,
Olea capensis and Croton megalocarpus seeds in Kakamega
forest and hence contribute to improved seed germination of
the three species
A. SPECIFIC OBJECTIVES
To determine the optimal timing of seed collection for
propagation of P. africana, O. capensis and C.
megalocarpus.
To determine the suitable media for optimum germination
of P. africana, O. capensis and C. megalocarpus seeds in
the nursery.
III. LITERATURE REVIEW
A. ECOLOGY AND BIOLOGY
This section highlights the ecological and biological
characteristics of Prunus africana, Croton megalocarpus and
Olea capensis.
a. PRUNUS AFRICANA (AFRICAN CHERRY) –
FAMILY ROSACEAE
Prunus africana is a member of the Rosaceae (subfamily
Amygdaloideae), a family with its highest diversity in
temperate regions. Although the relationships among the other
subfamilies of Rosaceae and its purported sister groups are yet
to be determined (Hall et al., 2000), the family is generally
considered monophyletic (Judd et al., 1999). The genus
Prunus is the largest member of the subfamily, and includes
the commercially important cherry (P. avium L.), peach (P.
persica L.), plum (P. domestica L.), and almond (P. dulcis. P.
africana is the only member of the genus on the African
continent and may be chemically distinctive.
Prunus africana is a medium–large canopy tree 30–40m in
height. Young trees have smooth, reddish bark whereas older
trees have dark, platy, resinous bark. Leaves are simple and
alternate. They are evergreen but some fall prior to fruit
development. Leaves, twigs, fruits, and bark emit a “cherry”
odor when crushed, which is characteristic of the genus. The
odor is due to cyanogenic glycosides (Richard et al., 2017).
The adult tree flowers between November and February,
although sporadic inflorescences can be found all year round
in some forests. The fruit develops within 4 to 6 months of
pollination. The ellipsoidal fruit is about 7–8mm in width and
10–12mm in length and contains one or two small oval seeds
(Beentje 1994). There are 3400–6000 seeds per kilogram on
average (Hall et al., 2000). The seed is spread by birds and this
is shown by the sprouting seedlings under big trees on the
forest floor.
P. africana has a wide distribution in Africa. It occurs in
montane regions of central and southern Africa and the islands
of Bioko, Sao-Tome, and Grande Comore (Dawson et al,
2000). P. africana is most abundant in open areas along forest
margins and in disturbed areas (Ndam, 1996) and is not shade-
tolerant (Kiama and Kiyiapi, 2001). Ndam (1996) also found
the most seedlings in forest gaps or fallow fields. This
suggests that P. africana is a light-demanding, secondary-
forest species. Recruitment is low or sporadic (Ewusi et al.,
1992). Because of deforestation at lower elevations, P.
africana is confined to distinct “forest islands” that differ
genetically (Barker et al., 1994), with the Madagascar
population being the most distinct (Dawson et al., 2000). The
tree occurs at altitudes between 1000 and 2500m in montane
forests (Sunderland and Tako, 1999). Distribution appears to
be related to mean annual temperature and rainfall and/or
cloud cover (Hall et al., 2000). Because of their relatively
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International Journal of Innovative Research and Advanced Studies (IJIRAS)
Volume 5 Issue 8, August 2018
ISSN: 2394-4404
large areas of montane habitat, Cameroon and Madagascar
contain the largest populations of the species. In Kenya, it is
common in Mt. Kenya, Aberdares, Kakamega, and
Cherangani Forests. It also occurs in Timboroa, Nandi, Tugen
hills and western part of Mau Forest.
b. OLEA CAPENSIS (ELGON TEAK) – FAMILY
OLEACEAE
Olea capensis is often a bushy shrub or a small to medium
sized tree up to 10 m in height, but it may be much larger,
occasionally reaching 40 m; occurring in bush, littoral scrub
and evergreen forest. Bark: light grey, becoming dark grey and
vertically fissured with age; a characteristic blackish gum is
exuded from bark wounds Fruits are ovoid, fleshy, up to 2 x 1
cm, when ripe they are somewhat succulent purplish drupes.
Flowering in profusion apparently takes place only at irregular
intervals of up to 7 years in the late dry season. The fruits take
about 6 months to ripen. Seed storage behaviour appears to be
orthodox. Growth is reported fast in young plants but much
slower in older ones. Over the first 4 years a mean annual
height of 1.1 m has been reported. It is a shade-tolerant,
pioneer species and a dominant forest tree (Kiama and
Kiyiapi, 2001).
c. CROTON MEGALOCARPUS (CROTON) – FAMILY
EUPHORBIACEAE
Croton megalocarpus is a hardy and fast-growing tree that
grows to 15-35 m with a distinctive layering of branches and a
rather flat crown. The bark is dark grey, rough, and crackling.
In Kenya, seeds mature during October-November in central
regions, and from January to March in Western regions
(Kiama and Kiyiapi, 2001). C. megalocarpus is a pioneer
species and it is found growing in cleared parts of natural
forests, forest margins or as a canopy tree. The species
regenerates well through seedlings, and under favorable
climatic conditions may sometimes become invasive. Young
trees coppice well after pruning, but fruiting is unlikely with
intensive pruning, such as in hedgerow management. In
agroforestry systems, it is sometimes managed as scattered
trees in farmland because of its open canopy and usefulness
for mulching. The seeds are extracted from the shell by
cracking with a hammer or a stone. On average there are 1700
seeds/kg. The seeds are dried in the sun to approximately 5-
9% moisture content and thereafter can be stored up to 1 year
at 3°C. After sowing, the seeds germinate within 35-45 days,
attaining germination rates of 95% without any pretreatment
(Maroyi, 2010).
d. TAXONOMY AND NOMENCLATURE OF PRUNUS
AFRICANA
Prunus africana is a member of the Rosaceae (subfamily
Prunoideae), a family with its highest diversity in temperate
regions (Clemente et al, 2006). Although the relationships
among the other subfamilies of Rosaceae and its purported
sister groups are yet to be determined (Hall et al., 2000), the
family is generally considered monophyletic (Judd et al.,
1999). The genus Prunus is the largest member of the
subfamily and includes the commercially important cherry (P.
avium L.), peach (P. persica L.), plum (P. domestica L.), and
almond (P. dulcis. P. africana is the only member of the genus
on the African continent and may be chemically distinctive.
e. BOTANICAL DESCRIPTION
Prunus africana is a medium–large canopy tree 30–40m in
height. Young trees have smooth, reddish bark whereas older
trees have dark, platy, resinous bark. Leaves are simple and
alternate. They are evergreen but some fall prior to fruit
development. Leaves, twigs, fruits, and bark emit a “cherry”
odor when crushed, which is characteristic of the genus. The
odor is due to cyanogenic glycosides (Richard et al., 2017).
f. DISTRIBUTION AND HABITAT
P. africana has a wide distribution in Africa. It occurs in
montane regions of central and southern Africa and the islands
of Bioko, Sao-Tome, and Grande Comore (Dawson et al,
2000). P. africana is most abundant in open areas along forest
margins and in disturbed areas (Ndam, 1996) and is not shade-
tolerant (Kiama and Kiyiapi, 2001), (Ndam 1996) also found
the most seedlings in forest gaps or fallow fields. This
suggests that P. africana is a light-demanding, secondary-
forest species. Recruitment is low or sporadic (Ewusi et al.,
1992). Because of deforestation at lower elevations, P.
africana is confined to distinct “forest islands” that differ
genetically (Barker et al., 1994), with the Madagascar
population being the most distinct (Dawson et al., 2000). The
tree occurs at altitudes between 1000 and 2500m in montane
forests (Sunderland and Tako, 1999). Distribution appears to
be related to mean annual temperature and rainfall and/or
cloud cover (Hall et al., 2000). Because of their relatively
large areas of montane habitat, Cameroon and Madagascar
contain the largest populations of the species. In Kenya, it is
common in Mt. Kenya, Aberdares, Kakamega, and
Cherangani Forests. It also occurs in Timboroa, Nandi, Tugen
hills and western part of Mau Forest.
g. FRUIT AND SEED PHYSIOLOGY AND
PHENOLOGY
The adult tree flowers between November and February,
although sporadic inflorescences can be found all year round
in some forests. The fruit develops within 4 to 6 months of
pollination. The ellipsoidal fruit is about 7–8mm in width and
10–12mm in length and contains one or two small oval seeds
(Beentje 1994). At maturity the fruits are dark red or reddish-
brown.
The seeds are oval and delicate There are 3400–6000
seeds per kilogram on average (Hall et al. 2000). The seed is
spread by birds and this is shown by the sprouting seedlings
under big trees on the forest floor.
h. REGENERATION, SOWING AND GERMINATION
The unit for sowing is the depulped fruit (the stone).
Germination normally takes place within 30-50 days (Orwa et
al, 2009). In nature, a fruiting tree can produce thousands of
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International Journal of Innovative Research and Advanced Studies (IJIRAS)
Volume 5 Issue 8, August 2018
ISSN: 2394-4404
seedlings (wildings) that can be collected and transplanted.
However, it is often seen that the wildings do not transplant
well. In Cameroon the species has been propagated from
cuttings. Without the use of hormones, about 10% of the
seedlings had rooted after three months (Hall et al, 2000). This
therefore indicates the difficulty in propagation. In terms of
natural regeneration, this species shows low or sporadic
recruitment (Ewusi et al, 1992).
B. USES OF P. AFRICANA
P. africana trees are an important part of the montane
ecosystem. It should therefore be noted that tree deaths from
bark stripping affects the integrity of the forest and reduces
food resources for rare birds (Cunningham & Mbenkum,
1993).
P. africana is a very useful tree both at local and global
markets. It takes fifteen years for the bark to develop the
active ingredients necessary for medicinal use (Hall et al,
2000). Traditional medicinal uses of the bark include the
treatment of stomach aches, urinary and bladder infections,
chest pain, malaria, and kidney disease. It also provides
durable timber for different household purposes.
a. TIMBER
The durable timber of P. africana makes it a favoured of
wood for household purposes, the type of use being dependent
on tree diameter and form (straightness) and local lifestyle.
Small trees are a source of axe and hoe handles (Neuwinger,
2000) and grinding pestles (Bwindi forest, Uganda)
(Cunningham, 1993). In western Uganda, large P. africana
trees are a popular source of “beer boats” for making banana
beer (Cunningham, 1993). In southern Africa the wood has
been used for timber and wagon making (Dawson et al, 2000).
b. MEDICINAL USES
P. africana is widely used in traditional medicine in
southern, east and central Africa (Neuwinger, 2000). The bark
is not only used by traditional healers, but also by local people
collecting their own medicinal extracts, including for use as a
purgative for cattle (Ewusi et al, 1996). In the Mount
Cameroon area, for example, 88% of people collect traditional
medicines of which P. africana was the fourth most popular
medicinal plant species amongst people interviewed around
Mount Cameroon and was collected by 14% of households
surveyed (Betti and Ambara, 2011). Similarly, it is an
important medicine in the Ijim montane forest area, where it is
used to treat malaria, stomach ache and fever (Neuwinger,
2000).
Prostate gland hypertrophy and the closely related but
more serious condition, benign prostatic hyperplasia (BPH)
are common diseases affecting older men worldwide. They are
expected to become more common amongst the ageing male
population of Western Europe and the USA. It is now
expected that one out of every two men in western countries
will live longer than 80 years, with the result that 88% have
the chance of developing histologic evidence of BPH. In the
USA, for example, a 40-year-old man has at least a 10%
chance of needing surgery for BPH, and in a recent survey in
Scotland, 30.2% of a random sample (492) of otherwise
healthy men aged between 40 and 79 years had prostatic
enlargement and symptoms of BPH. Treatments for this
disorder include surgery, balloon dilation, hyperthermia (using
urethral probes), phytotherapy and pharmaceuticals containing
anti-androgens and 5-alpha reductase inhibitors. Although
surgery is common and effective, it is expensive, can cause
impotence and is potentially dangerous, with a 1-3% post-
operative mortality. For this reason, medical therapy and
phytotherapy are popular alternatives. Nearly 30 years ago, P.
africana bark extracts were identified and patented as active in
the treatment of benign prostatic hypertrophy. Bark extracts
contain fatty acids, sterols and pentacyclic terpenoids. The
sitosterol glucoside content of P. africana bark is 11 mg 100g-
1 bark (Richard et al, 2017). Extracts of P. africana bark have
been shown to be effective on rats and in recent clinical trials
conducted in Austria. Capsules containing bark extracts have
been marketed in Europe (mainly Austria, France, Italy and
Switzerland) for over 20 years. By contrast with an earlier,
small clinical trial which showed no significant difference
between patients treated with “Tadenan” and a placebo
(Nyamai et al, 2016), the recent, detailed clinical trial
conducted by (Richard et al.,2017) showed that 66% of
patients treated with “Tadenan”, containing P. africana bark
extract, had improved urine flow compared to 31% with the
placebo. Five patients out of the 263 patients involved in the
study showed gastro- intestinal side effects.
c. VOLUME AND ECONOMIC VALUE OF P.
AFRICANA BARK TRADE
At least four European companies have interests in P.
africana bark for medicinal purposes: Laboratoires Debat
(France) and its subsidiary company Plantecam Medicam in
Cameroon; Madaus (Germany, Spain); Prosynthese (France);
Inverni della Beffa and Indena Spa (Italy). Bark is bought for
150-170 CFA kg-1 (US$ 0.6-0.7) in Cameroon and for 11
French francs kg-1 (US$ 2) from Kenya. Capsules containing
the bark extract are marketed in Europe, a 15-tablet box
costing US$ 7-8. The market value of this trade has been
roughly estimated at US$ 150 million a year (Luke et al,
2013). The Italian companies import bark extract from
Madagascar and the other European companies import
processed or unprocessed bark from Cameroon, Kenya,
Uganda and Zaire. Extract in tablets or capsules are marketed
under two main trade names: “Tadenan”, produced by
Laboratoires Debat (France) and “Pygenil” produced by
Indena Spa (Italy).
d. HISTORY OF EXPLOITATION OF PRUNUS
AFRICANA
For about 42 years, the African cherry has been used in
the treatment of benign prostatic hyperplasia and other
disorders (Richard et al, 2017). The bark, from which the
treatment is derived, is entirely wild-collected. The major
exporters of bark include Cameroon, Madagascar, Equatorial
Guinea, and Kenya (Betti and Ambara, 2011). Groupe
Fournier of France and Indena of Italy produce 86% of the
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International Journal of Innovative Research and Advanced Studies (IJIRAS)
Volume 5 Issue 8, August 2018
ISSN: 2394-4404
world‟s bark extract, both for their own products and for the
free market. Worldwide exports of dried bark in 2000 have
been estimated at 1350–1525 metric tons per year, down from
its peak of 3225 tons in 1997. Bark extracts (6370–7225 kg
per year) are worth an estimated $4.36 million per year
(Bodeker et al, 2014). In 2000, Plantecam, the largest bark
exporter in Africa, closed its extraction factory in Cameroon,
due to complex ecological, social, and economic factors.
Wild-collection is no longer sustainable (and probably never
was) where harvest seriously affects morbidity and mortality
rates of harvested populations. Prunus can be considered at
least as an endangered plant species in Cameroon according to
population reduction as outlined in the IUCN check list for
Non-Detriment Findings (Sunderland and Tako, 1999). This
explains the ban pronounced on October 2007 by the
European Commission on Cameroon‟s Prunus (Bodeker et al,
2014). The Prunus ban impacts both the economic operators
and the local people for whom Prunus represents an important
non-timber forest product. Cameroon was proposed for ban as
there are concerns that some provisions regarding the
sustainable harvesting of Prunus barks are not being fully met
(Betti and Ambara, 2011).
In Kenya, P. africana is present in most forested areas
above 1500m (Hall et al., 2000). Bark is harvested on
privately owned forest land when it is converted to tea estates,
resettlement lands, and other uses; harvest is forbidden from
protected areas (Cunningham et al., 1997). The species is
exported as dried bark, chipped bark, and timber. Harvest
began in 1995 with the export of 150 tons of bark. Export
peaked at 500 tons in 1998 and about 300 tons were shipped in
2000. Only one exporter (Jonathan Leakey) has been involved
in the Prunus africana trade in Kenya (Nzilani, 2001) and he
ships dried or chipped bark to Prosynthese (a subsidiary of
Groupe Fournier of France).
The CITES management authority for Kenya objected to
the continued harvest without a Detriment Study and halted
the harvest at the end of 2002. Cultivation trials have been
conducted, but large-scale plantations are not yet in production
(Barker et al., 1994; Dawson, 1997). Mature trees are also
exploited for their timber. Following harvest of mature trees
for local and export timber products (Nzilani, 2001) examined
the Kakamega and South Nandi forests in western Kenya. She
found few saplings and young trees, suggesting poor
recruitment resulting from the removal of mature trees.
e. CONSERVATION EFFORTS OF P. AFRICANA
Alternatives to wild-collection of P. africana must be
investigated, including the implementation and enforcement of
conservation measures as well as efforts to cultivate the
species. Several aspects of conservation have therefore been
considered as follows:
f. CULTIVATION
Over 35 years of wild-collections have led to serious
resource depletion that appears to threaten the resource.
Cultivation may be one mechanism to protect the resource
baceause It is light demanding and responds well to cultivation
(Hall et al., 2000; Tchouto, 1996). The Conservation through
Cultivation Programme at the Limbe Botanic Garden in
Cameroon and the International Centre for Research in
Agroforestry (ICRAF) cultivation experiments in Kenya are
leading cultivation efforts. (Cunningham and Mbenkum,
1993) recommended P. africana plantations at low altitude,
especially in areas of abandoned oil palm stands. However,
trees at low altitudes are more likely to become infested with
wood borers and fungal pathogens, seriously reducing timber
value (Cunningham et al., 2002). Available land at higher
altitudes is scarce, at least in Cameroon; nearly all lands
outside of forest preserves have been converted to farm crops
or pastures.
g. ENRICHMENT PLANTINGS
Enrichment plantings have long been recommended as a
way to replace the trees lost to harvest. In 1972, the Cameroon
Office National des Eaux et Forˆets (ONADEF) established an
enrichment plantation in Ntingue near Dschang.
Unfortunately, these forest reserve trees reportedly were
recently debarked (Cunningham et al., 2002). The Forest
Department of Kenya has started enrichment plantings for
timber production (Dawson et al., 2000). No enrichment
plantings are known for Madagascar but, considering that the
species is genetically unique (Dawson and Powell, 1999),
enrichment plantings may be critical where harvesting has
removed mature trees.
Vegetative techniques, such as grafting and cuttings
(Leakey, 1994) may be used in this case to speed the recovery
in denuded Madagascar forests as well as other heavily
harvested areas, such as the Bamenda Highlands of Cameroon.
Where enrichment plantings occur, they should include
opening the canopy and clearing the competitive undergrowth
around reproductive trees (Ndam, 1996). However, plantings
must not occur to the detriment of other forest species. With
the large market potential for future bark sales, it could be
tempting to manage a natural forest for P. africana production
(Cunningham et al., 2002) conducted an economic analysis of
enrichment plantings in Cameroon. Based on the historical
annual bark volumes processed at Plantecam (1923 tons per
year), they calculated that a 12-year-old stand on 820 ha with
1363 trees planted per hectare would supply enough bark for a
12-year rotation.
h. EX SITU CONSERVATION PRACTICES
(Barker et al., 1994) and (Dawson and Powell, 1999)
showed the genetic uniqueness of each country‟s populations.
Even within an area, the species demonstrates differences
(Cunningham et al., 2002) discusses three different varieties in
Cameroon reported by harvesters. Secure field gene banks
have been recommended (Cunningham and Mbenkum, 1993;
Cunningham et al., 2002) as a mechanism to conserve the
different genetic strains. Further, the harvest of populations of
P. crassifolia, possibly a separate species endemic to the Kivu
region of the Democratic Republic of Congo, may cause
severe population decline before science has a chance to
examine it. Thus, it is critical to establish secure field gene
banks for established P.
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International Journal of Innovative Research and Advanced Studies (IJIRAS)
Volume 5 Issue 8, August 2018
ISSN: 2394-4404
africana and P. crassifolia genotypes (Cunningham et al.,
2002). The felling or girdling of large reproductive trees
reduces seed production and possible recruitment (Stewart,
2001) documented the large numbers of seeds produced by
large trees and her model simulations showed the importance
of conserving large trees. A reduction in seed and animal
dispersal may further isolate the montane populations. Storage
of seed as a conservation strategy does not appear to be
possible (Sunderland and Nkefor, 1996) demonstrated the
recalcitrant nature of P. africana seed, which fails to germinate
if stored for more than 18 months.
i. CONVENTION OF INTERNATIONAL TRADE IN
ENDANGERED SPECIES (CITES) OF FLORA AND
FAUNA
CITES is the principal international conservation strategy
for the protection of internationally traded endangered species.
In 1994 (effective in 1995), P. africana was included in
Appendix II as an endangered species. Listing specifies that
trade in wild and cultivated material must be licensed in
exporting and importing countries. Difficulties in
identification of the various P. africana products have been
cited as a problem in its effective implementation, especially
in importing countries (Cunningham et al., 1997). This has led
to under-reporting of the trade. In addition, some countries
lack independent scientific CITES Authorities, allowing
exports to occur without a valid non-detriment finding.
(Cunningham et al., 1997) made several recommendations to
improve CITES oversight.
C. ELGON TEAK (OLEA CAPENSIS) – FAMILY
OLEACEAE
Olea capensis is often a bushy shrub or a small to medium
sized tree up to 10 m in height, but it may be much larger,
occasionally reaching 40 m; occurring in bush, littoral scrub
and evergreen forest. Bark: light grey, becoming dark grey and
vertically fissured with age; a characteristic blackish gum is
exuded from bark wounds Fruits are ovoid, fleshy, up to 2 x 1
cm, when ripe they are somewhat succulent purplish drupes.
Flowering in profusion apparently takes place only at irregular
intervals of up to 7 years in the late dry season (Orwa et al,
2009). The fruits take about 6 months to ripen. Seed storage
behavior appears to be orthodox (Albrecht, 1993). Growth is
reported fast in young plants but much slower in older ones.
Over the first 4 years a mean annual height of 1.1 m has been
reported. It is a shade-tolerant, pioneer species and a dominant
forest tree.
a. USES OF O. CAPENSIS
MEDICINAL VALUE - Bark is chewed or boiled to make
tea that helps in reducing fever; treating venereal diseases and
stomach problems.
TIMBER – The wood makes a fine, high quality timber. It
has dark brown heartwood and is attractively figured, fine-
grained, hard and heavy. It has been widely used in railway
sleepers, wagon woods, bridge construction and for flooring
blocks. It can also produce beautiful furniture (Neuwinger,
2000).
FUEL - A viable species for fuel wood from which
excellent charcoal can be made.
FODDER - O. capensis is a useful fodder tree.
b. CROTON (CROTON MEGALOCARPUS) – FAMILY
EUPHORBIACEAE
Croton megalocarpus is a hardy and fast-growing tree that
grows to 15-35 m with a distinctive layering of branches and a
rather flat crown. The bark is dark grey, rough, and crackling.
In Kenya, seeds mature during October-November in central
regions, and from January to March in Western regions
(Kiama and Kiyiapi, 2001). C. megalocarpus is a pioneer
species and it is found growing in cleared parts of natural
forests, forest margins or as a canopy tree. The species
regenerates well through seedlings, and under favourable
climatic conditions may sometimes become invasive (Maroyi,
2010). Young trees coppice well after pruning, but fruiting is
unlikely with intensive pruning, such as in hedgerow
management. In agroforestry systems, it is sometimes
managed as scattered trees in farmland because of its open
canopy and usefulness for mulching. The seeds are extracted
from the shell by cracking with a hammer or a stone. On
average there are 1700 seeds/kg. The seeds are dried in the sun
to approximately 5-9% moisture content and thereafter can be
stored up to 1 year at 3°C. (Maroyi, 2010) noted that after
sowing, the seeds germinate within 35-45 days, attaining
germination rates of 95% without any pretreatment.
d. USES OF C. MEGALOCARPUS
MEDICINAL VALUE - The bark is boiled to make tea
which is taken for treatment of whooping cough and a remedy
for worms. The leaves, roots, and bark are used to treat
stomach problems and pneumonia (Neuwinger, 2000).
FODDER - The seed finely ground is incorporated in
poultry feeds, as its protein content is high (50%).
FUEL - Well-dried nuts are reportedly used in some areas
together with charcoal in cooking stoves. The tree is also
utilized for firewood.
APICULTURE - This species produces a dark-ambered
honey with strong flavour.
TIMBER - Wood is of medium weight, hard, termite-
resistant, and strong; it is used for timber and building poles.
SHADE - C. megalocarpus forms a flat crown and has
horizontal layers of branches, which make it useful in
providing light shade and serving as a windbreak.
SOIL IMPROVER - Leaves have high levels of nitrogen
and phosphorus and serve as a source of mulch, for instance,
in coffee plantations.
ORNAMENTAL - Its conspicuous flowers make it suitable
as an ornamental.
BOUNDARY - As the species is not browsed by livestock;
it is often used as a live hedge (Salatino et al, 2007).
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International Journal of Innovative Research and Advanced Studies (IJIRAS)
Volume 5 Issue 8, August 2018
ISSN: 2394-4404
D. RESEARCH GAPS ON THE PROPAGATION AND
REGENERATION OF P. AFRICANA, O. CAPENSIS
AND C. MEGALOCARPUS
Most studies on the propagation and regeneration of P.
africana, O.capensis and C.megalocarpus have focused on the
harvested, treated and stored seed. Less attention has been
given to the stage of maturity for harvesting the seed for
propagation. For instance, (Luke et al, 2013; Sunderland and
Nkefor, 1996) demonstrated the recalcitrant nature of P.
africana seed. On the other hand, (Orwa et al, 2009)
demonstrated the orthodox seed behaviour of C.
megalocarpus. (Orwa et al, 2009, Albrecht, 1993) noted that
seed storage behaviour of O. capensis appears to be orthodox.
Different studies have also been done to identify the ideal
medium for seed germination but few have focused on the
different ratio of mixing different medium types.
Studies indicate that the natural regeneration for P.
africana species is poor (Luke et al., 2013) and recruitment is
low or sporadic (Ewusi et al., 1992). This is due to the fact
that the species is not shade tolerant. The same was observed
by Kiama and Kiyiapi, 2001; Dawson et al, 2000. However,
several authors noted that the species is light demanding. (Hall
et al., 2000; Tchouto, 1996) (Maroyi, 2010) noted that C.
megalocarpus regenerates well and under favourable
conditions may sometimes become invasive. On the other
hand, O. capensis trees showed good regeneration and
establishment away from adult trees. (Tsingalia and Nyongesa,
2010) noted too that O. capensis in Kakamega forest does not
show any evidence of natural regeneration under the parent
trees. It is a shade-tolerant, pioneer species and a dominant
forest tree (Orwa et al, 2009).
Despite these numerous research, stage of seed maturity
for propagation has been understudied. there has also been
limited studies on the medium used for propagation and the
site conditions for regeneration of these species.
E. CONCEPTUAL FRAMEWORK OF THE STUDY
The optimal timing of seed collection for propagation impacts on
the germination results of a specific species. The results of
germination are affected by the type of medium used for
propagation. The conceptual framework (Figure 1) identifies and
suggests the timing of seed collection, suitable media for
germination of Prunus africana, Croton megalocarpus and Olea
capensis that can improve the seed germination results.
Figure 1: Conceptual Framework for the study in Kakamega
Forest
IV. DATA ANALYSIS/ FINDINGS
A. DATA ANALYSIS
Summary of data analysis is provided in Table 1. Analysis
was carried out using Minitab and Excel. Descriptive statistics
are presented in terms of means and standard deviation.
Inferential test was also conducted where data was subjected
to tests of normality and homogeneity of variance and where
these assumptions were not met, they were log transformed.
Comparisons were conducted using parametric and non-
parametric tests (Analysis of Variance, Chi-square test, moods
median tests and Mann-Whitney tests). Post hoc tests (Tukey
tests) were also conducted to identify treatments that were
significantly different.
Objective
Data analysis
tools
Objective 1: To determine the optimal
timing of seed collection for
propagation of P. africana, O.
capensis and C. megalocarpus
One-way
ANOVA, moods
median test, Chi-
square test
objective 2- To determine the suitable
media for optimum germination of P.
africana, O. capensis and C.
megalocarpus seeds in the nursery
one-way ANOVA,
moods median
test, Chi-square
test
objective 3 - To compare propagation
and regeneration of P. africana with
that of Olea capensis and Croton
megalocarpus in Kakamega forest.
one-way ANOVA,
mann-whitney test
Table 1: Data analysis conducted on each objective
B. RESULTS AND DISCUSSION
This section describes in detail the results that were
observed and recorded from the experiments. It highlights the
effects of timing seed for collection on the germination and
also the effect of the type of media used for sowing the seeds.
a. EFFECTS OF SEED MATURITY STAGE ON
GERMINATION
The seeds of the species harvested at different stages of
maturity and sown responded differently in the different media
types. It took 28 days for P. africana seed that were harvested
when mature green to germinate in all the media types and
recorded germination rates of 97%. It took C.megalocarpus
seed 18 days to emerge and attained 52% germination rate.
Seeds harvested when mature ripe, it took 25 days for P.
africana seed to sprout in all the media types attaining
germination rate of 97% while C. megalocarpus seed took 15
days to sprout with final mean germination rate of 95%.
Stored seeds took 30 days for P. africana seed to sprout with a
mean germination rate of 13%. On the other hand,
C.megalocarpus seed took 15 days to sprout in all the media
types with 95% germination rate. O. capensis seed took 46
days to sprout in all the media types with 90% germination
rate (Fig. 2).
There was significant difference in the timing of the
collection of seeds for C. megalocarpus (F 2, 60, f=24.47,
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International Journal of Innovative Research and Advanced Studies (IJIRAS)
Volume 5 Issue 8, August 2018
ISSN: 2394-4404
P<0.001). A post-hoc test (Tukey test) showed that
germination rate was lower in mature green seeds compared to
the other two seed collection stages – mature ripe and stored
seeds (Fig. 3). There was significant seed timing effect (Chi-
square test = 32.90, d. f= 2, p < 0.001) for P. africana.
Germination rate was significantly lower in stored seeds
compared to the other two seed collection stages i.e mature
green seeds and mature ripe (Fig. 2).
Figure 2: Germination rates for the species at different stages
of seed maturity
Freshly harvested seed of P. africana germinates better
than stored seed because the seed loses viability upon storage.
Similarly, (Luke et al, 2013; Sunderland and Nkefor, 1996)
demonstrated the recalcitrant nature of P. africana seed. This
study therefore is in agreement that this seed is indeed
recalcitrant. On the other hand, good germination results of C.
megalocarpus were attained from stored seed because of its
orthodox seed behaviour (Orwa et al, 2009). (Maroyi, 2010)
noted that after sowing, C. megalocarpus seeds germinate
within 35-45 days contrary to the results of this study whereby
the seed germinated within 15- 18 days. (Orwa et al, 2009,
Albrecht, 1993) noted that seed storage behaviour of O.
capensis appears to be orthodox. This was similarly noted
because O. capensis stored seed attained germination rates of
90% from stored seeds.
b. EFFECT OF MEDIA TYPE ON GERMINATION
Germination rates showed different results in the different
„medium‟ types. Generally, sawdust gave low germination
rates while sawdust & sand (1:1) gave high germination rates.
There was a significant „medium‟ effect on the germination of
C. megalocarpus (F6,62, f=4.84, p<0.001), Prunus africana
(Chi- square test = 14.10, d. f= 6, p = 0.029) and O. capensis
(Chi –square test = 18.33, d.f= 6, p = 0.005). Seeds in sand
&sawdust 1:1 and sand had higher germination rate compared
to those in sawdust. Soil&sand 3:1 and soil had moderate
germination rate (figure 3).
Figure 3: Germination rates per species in different media
The „medium‟ that gave better germination results is
sand:sawdust 1:1 while „medium‟ sawdust gave poor
germination results. This is contrary to (Tchoundjeu et al,
2002) who indicated that the percentage of cuttings that rooted
was significantly greater in sawdust compared to a mixture of
sand and sawdust. Sand hastens germination through provision
of heat. It is also free from contamination. Therefore, when
mixed with sawdust, both play a role in that sand retains heat
while sawdust retains moisture thus providing conducive
environment necessary for germination.
V. CONCLUSION AND RECOMMENDATIONS
A. CONCLUSION
Based on the evaluations carried out, P. africana exhibits
good germination percent when propagated from seed freshly
harvested when mature and ripe even without any pre-
treatment. This is contrary to C.megalocarpus seed which
does not germinate well when it is propagated from freshly
harvested seed. Both O. capensis and C. megalorcapus
germinate well from stored seed. The best medium for
optimum germination of O.capensis, P.africana and
C.megalocarpus is sand: sawdust in the ratio 1:1 whereas the
medium that gives poor germination results is sawdust only. P.
africana is not shade tolerant and although wildings are in
plenty as observed in Kakamega forest, their recruitment is
poor. However, C. megalocarpus and O.capensis are good
natural regenerating species.
B. RECOMMENDATIONS
Based on the findings of the study, the following
recommendations are made:
P. africana seed should be sown immediately after
harvesting for optimum germination percent. On the other
hand, C. megalocarpus seed should be harvested as fruits,
dried thoroughly, extracted and sown. They can still be
stored well and sown later.
Since C.megalocarpus is a fast growing species with its
germination percent over 95%, it is recommended that
local communities should be informed about its multi-
purpose nature so as to ease the pressure currently on
P.africana.
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International Journal of Innovative Research and Advanced Studies (IJIRAS)
Volume 5 Issue 8, August 2018
ISSN: 2394-4404
Since O. capensis does not seed yearly, it is
recommended that the moment it seeds, a lot of it should
be propagated in the nursery and wildings collected for
seedling production.
The best medium recommended for optimum germination
of seed of all the three species is sand: sawdust in the ratio
1:1.
Since natural regeneration of P. africana is poor inside
the forest, it is recommended that wildings should be
collected in large numbers, raised in the nurseries and
used to rehabilitate degraded areas of the natural forests
due to their shade intolerance nature.
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