Analysis of phenophases that control in-situ establishment of Ocotea usambarensis Engl. in the southern slopes of Mt. Kenya Forest

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International Journal of Emerging Trends in Science and Technology
IC Value: 76.89 (Index Copernicus) Impact Factor: 4.849 DOI: https://dx.doi.org/10.18535/ijetst/v5i7.04
Analysis of phenophases that control in-situ establishment of Ocotea
usambarensis Engl. in the southern slopes of Mt. Kenya Forest
Authors
Rithaa J.N.1*, Magana A.M.2, Nduru G.M.2, Githae E. W2
1Department of Environmental Studies, Chuka University P.O Box 109-60400 Chuka
Email: jnrithaa@chuka.ac.ke /rithaajn@gmail.com
2Faculty of Science Engineering and Technology, Chuka University P.O Box 109-60400 Chuka
Email: egithaeh@gmail.com
Abstract
The existence of Ocotea usambarensis in Mt. Kenya Forest is threatened by extensive exploitation of both wood and
non-wood products and therefore requires urgent conservation measures to prevent further degradation. Assessing
phenological phases and their sequence determine the species establishment. This study therefore investigated the
phenology and establishment of O. usambarensis and its association with other plant species in Mt. Kenya Forest.
Three plots that were at least 5 km apart measuring 100 m x 100 m within the natural forest with mature O.
usambarensis species were purposely sampled on the southern slopes. Point centered quarter (PCQ) method was
applied in determining species association. Flowering, fruiting, leaf fall and leaf flush were determined as the main
aspects for phenological assessment. Data on environmental factors were monitored through the aid of automatic
weather station while phenophases were observed and recorded through classes of intensities. Shannon Wiener
diversity index was used to determine species diversity and importance while regression and correlation analysis
were used to determine the relationships among environmental factors. There was significant variation (P<0.05) in
flowering, litter fall and leaf flush. Mean flowering was 2.67 (42%) while no fruiting was observed during the study
period. Monthly variations in humidity, rainfall and radiation were significant (P< 0.05) while for temperature and
wind speed were insignificant. It was observed that Diospyros abyssinica was growing in close association with O.
usambarensis playing the role of nurse species. With the absence of seedlings in most of the sites and the limiting
environmental factors, promotion of vegetative propagation and enrichment planting would enhance conservation
and restoration of the species in Mt. Kenya forest
Keywords: Biodiversity, Conservation, Ocotea, Mt. Kenya and Phenology.
Introduction
Ocotea usambarensis is (Camphor) a tree species
with significant economic, environmental, social
and cultural importance. The species is found in
tropical forests which harbor between 50% and
90% of Earth’s terrestrial plant species
International Union for Conservation of Nature
and United Nations Environmental Programme
(IUCN & UNEP, 1992). Ocotea usambarensis
was once dominant in the wet forests of the
Eastern Aberdares and Mt. Kenya up to an altitude
of 2,600 meters above sea level, but is now rare
due to over-exploitation, low seed viability,
browsing, game damage and poor regeneration
(Gachathi, 2007). Germination of seeds is
sporadic often taking 2-3 months and the trees
mature in 60-75 years (Daniel et al., 2006).
According to Bussmann (2001), large scale
logging of Camphor trees predominantly destroys
its regeneration leading to secondary forest types.
The over exploitation, exploration and conversion
of forest ecosystems to different land use systems
normally result in the decimation of biodiversity
and extinction of many valuable indigenous plant
species and animals (Akotsi & Gachanja, 2004).
The indigenous tree species of economic
importance including O. usambarensis have low
density in tropical forests which indicates their
elimination due to the increasing demand for fuel
wood, timber and medicinal use (Maina, 2013).

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Ocotea usambarensisis is among the main
targeted timber species for selective logging
(Kleinschroth, et al., 2013). This is because of its
valuable wood for timber (Gathaara, 1999). Its
medicinal value and high quality timber has led to
its overexploitation endangering this unique tree
species. The extraction situation is compounded
by the slow growth rate, low seeds viability,
browsing by wild animals, game damage and
difficult in seedlings propagation (Albrecht, 1993;
Poorter et al., 1996). Other common species of
large timber trees exploited in Mt. Kenya forest
are; Juniperus procera (Cedar), Olea
europeae(Wild Olive), Hagenia abyssinica (East
African Rosewood), Croton macrostachyus
(Croton), Vitex keniensis (Meru Oak) and Ficus
thonningii(Strangler fig) (Mugumo (Beentje,
2008). Githae et al. (2015) reported that several
native tree species of environmental and socio-
economic value are threatened by human activities
and therefore should be conserved. There is a
wide range of biological diversity not only in
terms of ecosystems but also in terms of plant
species in Mt. Kenya ecosystem. According to
Bussmann, (2001) 882 plant species, subspecies
and varieties belonging to 479 genera and 146
families have been identified in Mt. Kenya forest
and out of these 81 plant species are endemic (
Gathaara, 1999). The identified main species in
the gazetted indigenous forests include;
Calodendrum capense, Catha edulis, Cordia
africana, Croton macrostachyus, Croton megaloc-
arpus, Ficus thonningii, Hagenia abyssinica,
Juniperus procera, Markhamia lutea, Milicia
excelsa, Ocotea usambarensis, Olea capensis,
Olea europaea, Olea welwitschii, Premna
maxima, Prunus africana and Vitex keniensis.
There are values attributed to Mt. Kenya forest by
all the various groups of people living around the
forest. The forest provides an important location
for religion and other rituals for the people. Many
tree species are considered sacred while others are
used for both socio economic and environmental
services. Its conservation preserves its vitality.
Sustainable utilization of O. usambarensis can be
achieved if adequate information on the
regeneration dynamics is available.
The government policy aims at promoting
commercial tree growing and on-farm species
diversification (GoK, 2014).Tree planting has
often focused on exotic species; however exotic
species have failed to replace indigenous timber in
places where high quality timber is needed for
furniture and interior furnishings (Oballa and
Musya, 2010). If Kenya is to earn more GDP from
forest products, these indigenous species must not
only be conserved but be improved and grown
side by side with the exotic ones. Communities
adjacent to Mt. Kenya forests depends on the
forests for timber, fuel wood, grazing areas and
non-timber forest products like honey harvesting,
medicinal extracts and domestic water. There is
ignorance amongst the surrounding communities
on ecological aspects including multiple values of
forest, the effect of forest over-use on their
livelihoods and for those downstream and
sustainable conservation strategies. Remnant trees
are retained in the farm lands of the local people
to improve livelihoods (Kewesa et al., 2015).
Degradation of Mt. Kenya forest is mainly due to
exploitation of indigenous trees for timber and
other uses coupled with lack of local forest
inventories (Rutten, et al., 2015). Information on
the various aspects of establishment of the most
demanded forest species is necessary for their
domestication with the aim of easing pressure on
their in- situ exploitation since ex- situ production
could be achieved. Adoption and domestication of
much sort for forest woody species including
Ocotea usambarensis would in turn lead to the
protection and restoration of natural forest
habitats.
Ocotea usambarensis has prospects as a plantation
timber tree providing wood of excellent quality.
Marura and Lemmens (2008) observed that
although the species provides valuable timber and
has been over exploited, very little research has
been done on its growth rates, phenological and
regeneration responses to environmental cues.
Kleinsclhroth, et. al (2013) reported that natural

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regeneration of O. usambarensis in Mt. Kenya
forest is inadequate for the recovery of the
valuable timber species and additional
conservation measures should be considered. The
farmers have not succeeded in planting the O.
usambarensis seedlings on their farm due to lack
of information on the species ecological
requirements and management. The Kenya Forest
Service and timber merchants have also not
succeeded in establishing the O. usambarensis
plantations for commercial growing. The specific
fertility requirements for the seedlings
establishment need to be ascertained for ex-situ
management. This study was designed to
establish the environmental factors that influence
phenology, regeneration and establishment of O.
usambarensis and inform the requirements for its
conservation and management.
Materials and Methods
The study involved use of various materials and
equipment: Automatic weather station (AWS) was
mounted for monitoring the environmental
factors, Global Positioning System (GPS) for
marking the coordinates of the plots location and
Diameter tape for measuring the DBH.
Study Site
The study was carried out in the southern slopes
of Mt. Kenya forest. Mt Kenya Forest is located to
the east of the Great Rift Valley, along Latitude 0’
10’S and longitude 37’ 20’E. It bestrides the
equator in the central highland zones of Kenya.
The mountain is situated in two Forest
Conservancies and five forest management zones
namely Nyeri and Kirinyaga in Central Highlands
Conservancy and Meru Central, Meru South and
Embu in Eastern Conservancy. The climate of Mt.
Kenya region is largely determined by altitude.
There are great differences in altitude within short
distances, which determine a great variation in
climate over relatively small distances. Average
temperatures decrease by 0.6 C for each 100m
increase in altitude. An afro-alpine type of
climate, typical of the tropical East African high
mountains, characterizes the higher ranges of Mt.
Kenya. The altitudes with the highest rainfall are
between 2,700 and 3,100m, while above 4,500m
most precipitation falls as snow or hail. Frosts are
also common above 2500 m a.s.l. The study was
on the altitude range of 1400-2400m a.s.l both for
on-farm and forest establishment (figure 1).
Figure 1: Map of the study area

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Climate
Rainfall pattern in the Mt. Kenya ecosystem is
bimodal and ranges from 900 mm in the north
Leeward side to 2,300 mm on the southeastern
slopes Windward side of the mountain (Survey of
Kenya, 1966) with maximum rains falling during
months of March to May and October to
November. The driest months are January,
February and September with the windward side
experiencing the strongest effects of wind. The
diurnal temperature range in January and February
rises up to20 °C. The diurnal variation causes
warm air to fall down the mountain during the
night and early morning and rise up the mountain
from mid-morning to evening. As a result, the
upper part of the mountain is usually clear in the
morning, clouded over from about 11.00 am to
5.00 pm and clear again shortly before dusk
(Kenya Forest Service, 2010).
Phenological assessment of Ocotea
usambarensis
Phenological events of mature O. usambarensis
were assessed during the study period. Flowering,
fruiting, leaf fall and leaf flush were determined as
the main aspects for phenological assessment.
During the peak flowering and fruiting,
observations were done every fortnight. Leaf
status, flowering (flower buds and open flowers)
and fruiting (unripe and ripe fruits) were recorded
using different classes of intensities; 0: (0%), 1:
(1-25%), 2: (26-50%), 3: (51-75%) and 4:
(>75%), with percentages referring to the
proportions of each phenophase in the crown.
Regeneration assessment of Ocotea
usambarensis
Three plots of 100 m x 100 m containing mature
tree species of O. usambarensis were marked
within the southern region of Mt. Kenya forest
using Global Position System (GPS)GPS for
phenologicaland biodiversity assessment. The
plots were 5 - 10 km apart. Point centered quarter
(PCQ) method was applied within the plot for
biodiversity determination. The initial sampling
points were purposely selected next to a mature O.
usambarensis tree. Following a perpendicular line
to either compass direction, other sampling points
were determined at 20 m interval. The diameter at
breast height (DBH) was measured for the nearest
tree species on either direction of the point. The
Ocotea usambarensis plants identified in the plots
were grouped as; >30cm for mature trees, 10-30
cm for saplings and < 10 cm for seedlings. The
status of regeneration was recorded as good if
seedlings and saplings >mature trees, fair if
seedlings >saplings and poor if mature trees
>seedlings. The mature plants were marked for
phenophases assessment.
Assessing environmental factors
Environmental factors that influence phenology
were monitored in relation to phenological phases.
Rainfall, temperature, relative humidity, radiation
and wind speed were monitored for 12 months
using Automatic Weather Station (AWS).
Data Analysis
Regression analysis was done to determine the
relationship between the environmental factors
whereas one – way analysis of variance
(ANOVA) (Zar, 1996) at P≤0.05 was performed
to describe the differences in growth variables.
Mean separation was done using the least
significance difference (LSD). Time series
analysis was used to evaluate the phenophases and
the environmental factors. Shannon-Weiner
diversity index (Magurran1988) was used to
determine species diversity. The Shannon-Weiner
index was calculated using the following
equation:
Results
The relationship between environmental
factors and phenological behavior of Ocotea
usambarensis
The variation in flowering, litter fall and leaf flush
was significant (P<0.05) whereas there was no
fruiting. Mean flowering was 2.67 (42%) while
fruiting was 0 (0%). Ocotea usambarensis
flowering was observed in all the mature species,

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however, the fruiting was rare. Seedlings were
observed at the Chogoria site. The mean leaf fall was 1.67 (17%) while the Mean leaf flush was
2.33 (33%) (Table 1).
Table 1: Phenophases of Ocotea usambarensis
Species Flowering Fruiting Leaf fall Leaf flush
Location % % % %
Kiang’ondu 3 0 1 2
Kiamuriuki 2 0 2 2
Chogoria 3 0 2 3
LSD (P<0.05) 2.67 0 1.67 2.33
0= 0%, 1= 1-25%, 2= 26-50%, 3= 51-75% and 4= >75%
Flower buds formed in January and opened in February while leaf fall occurred between March and June.
Leaf buds formed in July and leaf flush was observed in September and October (Figure 2).
Figure 2: Periodicity of Ocotea usambarensis phenophases
Environmental factors that influence
phenological behavior of Ocotea usambarensis
The environment parameters that influence
phenology of a plant were investigated. There was
significant (P< 0.05) monthly variation of
humidity, rainfall, and radiation. However
variations in temperature and wind speed were in
significant (P<0.05) during the study period. The
mean monthly records indicated the congruence
with the phenophases of O. usambarensis (Table
2).
Table 2: The monthly mean values of environmental factors
Month Humidity Rainfall Radiation Temperature Wind speed
November 64±7.9b 116.01±0.56d 348.58±21.42b 25.68± 0.82 1.32±0.23
December 65±8.3b 18.9±0.95b 315.68±22.46b 24.45±0.91 1.49±0.12
January 74±5.6c 12.3±0.45b 686.68±6.98d 21.98±1.31 1.59±0.08
February 56±10.1a 62±1.02c 408.98±18.13c 24.38±0.88 1.74 ±0.04
March 66±7.5b 131.8±3.45d 130.53±44.68a 23.37±0.63 1.64±0.70
April 59±9.7a 162.8±3.88d 136.62±43.12a 25.28±0.75 1.45±0.11
May 60±9.9a 29.88±1.01b 359.83±20.41b 24.67±0.91 2.05±0.02
June 71±5.3bc 1.04±0.01a 515.1±14.51c 22.59±1.10 1.93±0.03
July 63±8.1b 0a 629.1±8.22d 24.42±0.76 1.68±0.04
August 54±9.8a 0a 631.27±8.31d 24.96±0.86 1.82±0.03
September 68±8.2b 0a 642.30±8.45d 25.81±0.78 1.95±0.02
October 72±5.4c 78.54±2.21c 559.34±12.10c 24.27±0.90 1.88±0.03
Values followed by the same letter are not significantly significant at (P<0.05)
0
1
2
3
4
5
Phenophases
Peridicity of Phenophases of Ocotea usambarensis
Flowering
Fruiting
Leaf Fall
Leaf flush

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The relationship between the environmental
factors
The regression analysis depicted a linear
relationship (P <0.001) between the
environmental factors (Table 3). The relationship
between humidity and other parameters were
computed with humidity as the dependent
variable. There was a linear relationship (P<0.05)
between humidity and temperature (Table 4).
However, the relationship (P>0.05) was
curvilinear between humidity and precipitation,
humidity and Radiation and then humidity and
wind speed. A low P-Value suggests that the
humidity may be linearly related to other
parameters. The high value of R2= 0.8741
indicated that the precipitation, radiation,
temperature and wind speed explains 87.4% of the
variations of the humidity values.
Table 3: Regression relation for environmental factors
Source Sum of Sqs df Mean Sq F p-value
Regression 1221.3862 4 305.34656 12.706448 <.001
Error 648.83253 27 24.030834
Total 1870.2188 31
Table 4: Linear regression and correlation with humidity as the dependent variable
Variable Coefficient St. Error t-value p (2 tail)
Intercept 218.30673 30.516514 7.1537244 <.001
Precipitation -.0263778 .0347994 -.7579966 0.483
Radiation -.0102188 .0109452 -.9336291 0.393
Temperature -5.932943 1.0420372 -5.6936 0.002
Wind speed -4.36393 5.2888808 -.8251142 0.447
R-Square = 0.8741
There was a linear relationship (P<0.05) between
radiation and temperature. However, the
relationship (P>0.05) was curvilinear between
radiation and precipitation, Radiation and
humidity and then Radiation and wind speed
(Table 5).The high value of R2= 0.7828 indicated
that the precipitation, humidity, temperature and
wind speed explains 78.28% of the variations of
the radiation values.
Table 5: Linear regression and correlation with radiation as the dependent variable
Variable Coefficient St. Error t-value p (2 tail)
Intercept 4226.4333 3361.8277 1.2571832 0.264
Humidity -14.52746 15.5602 -.9336294 0.393
Precipitation -2.628165 .7334803 -3.583144 0.016
Temperature -113.5835 94.719461 -1.199157 0.284
Wind speed -29.51793 212.14883 -.1391378 0.895
R-Square = 0.7828
Effects of rainfall on Phenological phases
(flowering, fruiting leaf fall and leaf flush) of O.
usambarensis
Rainfall amounts and distribution plays a key role
in determining the phenological phases of the
species. Rainfall was distributed in all the months
in varying amounts except in July Augustand
September (Figure 3). The study area has two
rainy seasons, the long rains falling between April
and June and the short rains between October and
December with a mean annual rainfall of 1600 –
2450 mm. (Abeney and Owusu 1999).

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Figure 3: Rainfall and phenophases
Effects of temperature on Phenological Phases
(flowering, fruiting and leaf fall)
The average temperature in the study area ranges
from 21oC to 26oC during the day (Figure 4).
Seasonal variations are distinguished by duration
of rainfall rather than by changes of temperature.
Figure 4: Temperature and phenophases
Effects of Humidity on Phenological Phases
(flowering, fruiting and leaf fall)
The highest (74) humidity was during the month
of January while the lowest (54) humidity values
were recorded in august. The highest humidity
coincided with the onset of flowering while
reduction in humidity was during the leaf fall
(Figure 5).
-20
0
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40
60
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120
140
160
180
J AN U AR Y
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Humidity
Rainfall and phenophases
Humidity
Flowering
Litter fall
Leaf Rush
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J AN U AR Y
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Temperature and phenophases
Humidity
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Leaf Rush

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Figure 5: Humidity and phenophases
Effects of solar radiations on Phenological
Phases (flowering, fruiting and leaf fall)
The average solar radiations received were low
during the month of April at 130. 53 and highest
at 642.3 during the month of September.
Flowering occurred during the low radiations.
Shedding of leaves also occurred during the low
radiations period, however, fruiting coincided
with exponential increase of radiations received.
Figure 6: Radiation and phenophases
Effects of wind speed on Phenological Phases
(flowering, fruiting and leaf fall)
The overall wind speed was steady with
insignificant variation. However, the wind speed
was highest during the month of May and June
during which seed shedding and leaf fall was
occurring (Figure 7).
0
10
20
30
40
50
60
70
80
J AN U AR Y
F EB R UA R Y
M AR C H
A PR I L
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Humidity
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Humidity
Flowering
Litter fall
Leaf Rush
0
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800
Radiations
Radiations and phenophases
Solar Radiations
Leaf flush
Litter Fall
Flowering

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Figure 7: Wind speed and phenophases
Overall mature trees of Ocotea usambarensis are
more than the regerants in the study area
(56.52%). Forty six percent of the mature species
were found in Chogoria forest while 30% was
found in Kiangondu forest and 23% in Kiamuriuki
forest. Eighty six percent of the seedlings were
found in Chogoria forest. There were no seedlings
and saplings in Kiamuriki (Table 6). Fair
regeneration was observed in Chogoria whereas
regeneration in Kiang’ondu and Kiamuriuki forest
areas was poor. Natural regeneration through seed
germination was seldom. The seedlings
observations were mainly of root suckers and not
seed germination.
Table 6: Distribution of O. Usambarensis within the study area
Species Mature % Saplings % Seedlings %
Location
Kiang’ondu 30.77 0.00 13.33
Kiamuriuki 23.08 0.00 0.00
Chogoria 46.15 100 86.67
Overall 56.52 4.35 39.13
Mature – DBH = >30cm, Sapling – DBH = 10cm - 30cm and Seedling – DBH =<10cm
Discussion
Influence of environmental factors on
phenological phases of Ocotea usambarensis
Phenology is the periodicity or timing of recurring
biological events. In the case of the study,
phenological events involved flowering, fruiting,
leaf fall and leaf flushing. The schedule of
phenological events has important effects on plant
survival, reproductive success, regeneration and
establishment.
Influence of environmental factors on
flowering of Ocotea usambarensis
Phenological phases varied with the
environmental factors prevalence. Flowering of O.
usambarensis occurred in the month of December
to February. These findings concurred with the
observation by Okeyo (2008) that in Chogoria
forest flowering of O. usambarensis occurs in
February. During this period the rainfall received
was minimal and the relative humidity relatively
high. The period is normally preceded by the short
rains season which is characterized by increased
vegetative growth. The hormonal activity for
flowering favours low humidity and relatively
high temperatures.
The O. usambarensis plants are proliferous in
flowering; however formation of seeds that can
develop to augment regeneration is rare. This is
0
0.5
1
1.5
2
2.5
Wind speed in M/S
Wind speed and phenophases
Wind speed
Flowering
Litter fall

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partly due to the dioecism characteristic of O.
usambarensis and the limiting environmental
factors. The curvilinear correlation between
rainfall and humidity indicates the need to
understand their role in controlling phenophases
of plants.
The study established that absence of seedlings in
most of the sites even with observed flowering
indicates that most of the flowering O.
usambarensis plants were males. The female
plants and the male plants should be at a
transmittable distance to enhance pollination and
subsequent reproduction of viable seeds. Travis
(2009) reported that O. usambarensis produces
seeds every ten years and that fresh seeds are
recommended to be used for sowing. The
germination rate is often low, up to 45 %because
seeds are often heavily attacked by insects. The
seeds usually start germinating in 30 – 45 days,
but germination may take up to 90 days Bussman
(2001). Kowalski and Van (2000) reported that,
propagation of Ocotea by seed is difficult as the
flowers and fruits are attacked by fungal diseases
and insects and the fruits quickly loose viability in
storage. Tonin (2006) also observed that storage
of Ocotea seeds decreased their viability and
vigor.
Dry season flowering in tropical forests may be
enhanced by the higher radiation as there was a
significant positive correlation with mean monthly
temperatures. Flowering was significantly
correlated to mean monthly temperature. Decrease
in temperature during the rainy season was
followed by significant increase in the flowering
individuals one month later. Flowering phenology
may also be triggered by the humidity
(Augspurger, 1981; van Schaik et al., 1993; Sakai,
2001; Anderson et al., 2005). The strong
correlations shows the importance of
environmental factors in regulating flowering of
O. usambarensis. According to Frankie et al.
(1974) wet season flowering in tropical dry forests
is low.
Influence of environmental factors on fruiting
of Ocotea usambarensis
Under favorable environmental conditions,
effective fruiting follows flowering. Seed
formation is dependent on the physiological
aspect of the plant and the prevailing
environmental factors. Ocotea usambarensis is
proliferous in flowering, however fruiting is
seldom. Low and sometimes lack of fruiting may
be due to unpleasant environmental conditions
that do not favor fruiting and insects attack on
flowers of O. usambarensis. Fruiting formation of
O. usambarensis occurs between February and
May during which time the long rainfall and
autumn conditions prevails. The seed maturity
occurs during the period when moisture is high to
favor germination.
Ocotea usambarensis seeds are sensitive to
desiccation and should be sown fresh.
Pretreatment of seeds is not necessary and under
ideal conditions, seeds germinate in 30 – 45 days
and the expected germination rate of mature,
healthy and properly handled seeds is 45 %,
Bussman (2001). Gachathi (2007) reported that
germination of O. usambarensis seeds is sporadic
often taking 2-3 months. The seeds usually start
germinating in 30 – 45 days, but germination may
take up to 90 days, Bussman (2001).The seeds
should be picked, cleaned and sown immediately
since they are recalcitrant. Tonin (2006) observed
that storage of O. usambarensis seeds decreased
their viability and vigour.
Solar radiations and Temperatures are generally
low during the period of seed maturation to reduce
the incidences of drying and subsequent loss of
viability. The rainfall season ensures increased
moisture content which is a requirement for
germination. Ocotea seeds in the wild are
parasitized and the regeneration potential is
reduced.
Effective O. usambarensis establishment both
vegetative propagation for in-situ and ex-situ
programme should be considered. Jaenickle and
Beniest (2002) reported that a piece of plant
material can grow to form a new plant that

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contains the exact genetic information of its own
source plant through vegetative propagation.
The individuals’ plants that flowered seldom
produced fruits implying that fruit production is
controlled and influenced by changes in
environmental factors. The flowering conditions
differed with the fruiting condition which
indicates reduced reproductive success in this
species. Abortion of immature fruits due to self-
pollination among out-crossing populations has
been reported in several tropical tree species
(Sakai et al., 1999). Regenerated young seedlings
on the forest floor were located far away from the
crown of the mother trees and mainly sprouting
from the roots. Fruiting phenology and
reproductive success of O. usambarensis was
influenced by both environmental and soil factors.
Influence of environmental factors on leaf fall
and leaf flush of Ocotea usambarensis
Ocotea usambarensis is partly deciduous. Leaf
fall and leaf flush of the deciduous species are
annual and strictly seasonal, and leaf fall peaks
during the long dry season when the temperature
is high. The periods of leaf fall and leaf flush were
overlapping. Annual pattern and strong
seasonality accords with leaf fall and leaf flush.
During the periods of low rainfall and high
temperatures the plant shed some of its leaf. The
shedding of the leaf coincides with the flowering
period. The leaf fall forms the floor layer that
enhances moisture conservation in readiness for
seed shedding and germination. The physiological
process also reduces the chances of transpiration
thus concentrating the chemical energy to the seed
development.
Temperatures, solar radiations and humidity were
relatively high at the period of leaf fall for which
additionally prepares the plant for leaf flushing at
the onset of the rain season (Figure 2). The wind
speed was also high during the period to facilitate
the leaf fall and spread on the floor surface. The
findings agrees with the report by (Justiniano and
Fredericksen, 2000) and cloud forest in Hawaii
(Berlin et al., 2000) that Leaf fall of deciduous
species in a Bolivian dry forest began at the
beginning of the dry season and continued until
the beginning of the rainy season. The significant
correlation between leaf fall and mean monthly
temperature suggests that leaf fall is an adaptation
to reduce the effect of water stress in the dry
season. The seasonality pattern of peak leaf fall
also agrees with reports from the Atlantic Rain
Forest Trees (Morellato et al., 2000) where leaf
fall consistently peaked during dry seasons when
there was high water stress (Anderson et al.,
2005). Borchert (1984) argued that the timing of
leaf fall is controlled by the water status of the
plant.
Influence of environmental factors on
regeneration of Ocotea usambarensis
The study established that the population structure
of O. usambarensis is characterized by high
proportion of mature individual with DBH> 30
cm and few regenerants with DBH<10cm, thus
unstable. The regenerants were observed from the
root system thus agreeing with Louppe, et.al,
(2008) in their report that under natural
conditions, O. usambarensis regenerates mainly
by suckers because undamaged seeds are
uncommon. After natural mortality of an old tree,
the gap is first filled by fast – growing pioneer
species, in the shade of which the Ocotea
usambarensis suckers can establish, and after
death of the pioneer species, they can develop into
new trees, Bussman (2001). It was observed that
in Mt. Kenya forest, Diospyros abyssinica was
growing in close association with O.
usambarensis playing the role of nurse species.
Canopy opening through both anthropogenic and
natural disturbance plays an important role in
determining population structure of O.
usambarensis. It was clear that a certain level of
canopy opening significantly increases the density
of young regenerants.
This study established that the number of
seedlings was low and influenced by canopy
opening which controls the light incidence.
Kleinschroth et al. (2013) reported that

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regeneration of O. usambarensis in Mt. Kenya is
generally low and negatively influenced by
historical logging, and that natural regeneration
was inadequate for the recovery of O.
usambarensis, and recommended enrichment
planting as additional conservation measures to
promote the species. It was observed that a high
percentage of old individuals and very low
recruitment of O. usambarensis mainly as root
suckers and few seedlings in previously heavily
logged areas at Mt. Kenya.
Ocotea usambarensis is mainly harvested from
natural stands, and the extent of plantations is very
limited. Its regeneration should be enhanced
through gapping in-situ as opposed to Bussman
(1999) who proposed that several valuable and
fast growing indigenous species including
Juniperus procera and Vitex keniensis could be
used for planting in gaps left by O. usambarensis
either in mixture or as nurse trees to promote the
regeneration of O. usambarensis. Ocotea
usambarensis trees can be managed by coppicing
to which they respond well at any age Palmer
(2000) and Okeyo (2008). The rotation cycles is
60 to 70 years however can be reduced to 50 years
with proper thinning regimes to finally 220
trees/ha. Newmark, 2002 reported that O.
usambarensis is known to experience low sexual
regeneration through seedlings while other studies
found that vegetative regeneration through suckers
was more important than sexual regeneration,
because the density of root suckers was found to
be 6 times higher than that of seedlings
(Kleinschroth et al., 2013). The characteristic of
O. usambarensis to produce many suckers after
disturbance should be used to devise a
management scheme for timber production
(Willan, 1965). Although germination of sown
seeds is fairly good (Msanga, 1998), seed viability
is very short and therefore precludes the formation
of a seed bank and dries out before reaching
potential regeneration sites (Bussmann, 1999;
Baskin and Baskin, 2005). Ocotea usambarensis
is considered to be a climax species although it
also exhibits characteristics of pioneer species.
Ocotea regenerates from suckers, coppices and
rarely from seed. At some stages of its growth it
behaves as a light demander than a shade tolerant,
Also, at any stage when camphor is felled, root
suckers are produced which, although able to
persist under shade, grow rapidly in half or full
light (Mugasha, 1996).
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