Should Woteva and Other Villages on the Foot of Mount Cameroon Grow Cedrela Trees?

 

Introduction:

Cedrela mexicana (odorata) Species come originally from the Latin American forest (Mexico to Ecuador, Peru, Brazil and French Guyana) and grows well in primary and secondary evergreen to semi-deciduous lowland and low mountainous forests (Orwa C, A Mutua, Kindt R, Jamnadass R, S Anthony, 2009). According to Mr Ndumbe Ekema Stephen of Wewuley Consultancy, the species was introduced in Cameroon by the Victoria Botanic Garden (now known as the Limbe Botanic Garden) in the 1950s and early 1960s. 

 

2-year-old Cedrela Farm in Woteva Village – May 2017

 

 According to recent preliminary research work carried out by Treff-End in collaboration with Wewuley Consultancy and the Woteva community, the Foot of Mount Cameroon seems to provide excellent conditions to grow this species. In a 2-year old demonstration farm in Woteva village, the average diameter at breast height (DBH) of Cedrela trees in the whole farm calculated from a sample of 254 trees (total population of 700 trees) is 5.7cm, giving an average annual increase in DBH of 2.8cm. Similarly, the average height in the farm calculated from the same sample is 4.357m, giving an average annual increase of 2.2m in height. These DBH and height values are slightly higher than the 2.5cm per year in DBH and 2m per year in height attributed to this species by most researchers.

 

In its native habitat in Latin America, Cedrela trees are often attacked by the Mahogany shoot-borer (Hypsipyla grandella), which reduces their growth rates and sometimes kill the trees. However, good results are obtained in Africa where the native shoot-borer does not attack the plant. These good results in Africa are also due to the presence of good and well-drained soils and the practice of agroforestry (Luren Ford, 1979).

 

Methods:

For this preliminary studies, the researchers concentrated on observing the behaviour of trees in the two demonstration farms in Woteva village. The values for the average DBHs and heights of trees in the two farms were collected from samples calculated from the tree populations. Samples were calculated using the equation provided by Krejcie & Morgan (1970).

s = X²NP(1-P) ÷ d² (N-1) + X²P(1-P)

Where s is the required sample size, X is the Z value at a 95% confidence level (1.96), N is the population size, P is the population proportion expressed as a decimal assumed to be 50% (0.5) and d is the degree of accuracy expressed as a proportion, and also known as the margin of error (0.05).

 

The researchers further collected data from five 3.5-year-old trees planted by Chief Bernard Lieti in another location in Woteva and three 36-year-old trees planted by Mr. Ndumbe Ekema Stephen of Wewuley Consultancy in Moyuka. All these trees in the demonstration farms and in those other locations were also carefully observed by eye for the presence of parasite attacks. DBHs of trees in the demonstration farms were calculated using a digital calliper while those from other locations were calculated using a measuring tape. The heights were estimated with the use of measuring sticks.

 

 

 Environmental data such as soil type, average rainfall and temperatures in the region were obtained from local research reports especially the Ministry of Forestry and Wildlife. The altitude and area of farms were calculated using a Garmin 64ST Satellite GPS. The collected values were compared with those of the ideal growth conditions attributed to this species by researchers. Finally, using the standard growth rates of 2.5cm per year in DHB and 2m per year in height, estimates of wood volume harvests in meter cubed after 10, 15 and 20 years were calculated. Given the tree DBH in centimeters (cm) measured 1.3m above ground level, tree height measured in meters (m), Π = 3.142 and assuming the tree is conical in shape with the DBH equivalent to the diameter at the base of the cone, the formula below was used to obtain conservative estimates of total under bark tree volume in meters cubed (m³) (Farm Forest Line, 2009):

Tree Volume (m³) = Tree Basal Area (m²) x Tree Height (m) / 3

                                  = (DBH/200)² x Π x h / 3

Finally, estimates of revenues were calculated for each tree and for one thousand trees after a period of 10, 15 and 20 years.

 

Results: 

Environmental conditions:

Item	Altitude	Temp.	Rainfall /yr	Soil Type
Ideal	0-1900m	22-33°c	1000-3700mm	Well-drained fertile, weakly acidic
Woteva	650-1300m	21-29°C	Above 3000mm	Well drained fertile volcanic, ixed with metamorphic rocks

 

DBH and heights in farms:

Item	Actual DBH	Actual height	DBH/yr	Height / yr	Buttress	Disease/Parasite
Average			2.5cm/yr	2m/yr	Narrow	Shootborer, worms
2015 Farm	2-11cm	1.6-10m	2.8cm/yr	2.2m/yr	Below 10cm	None
2016 Farm	0.8-3.4cm	0.5-2.8m	1.7cm/yr	1.4m/yr	Below 10cm	None

 

 Other trees:

3.5 yrs trees (5)	19.7cm	22.1m	5.6cm/yr	6.3m/yr	Below 20cm	None
36 yrs trees (3)	97.3cm	Above 50m	2.7cm/yr	1.6m/yr	1.3-1.4m	None

 

 Wood volume estimates per tree:

Tree age (yrs.)	DBH (cm)	Height (m)	Volume (m3)
10	25	20	0.33
15	37.5	30	1.10
20	50	40	2.26

 

Revenue estimates:

Tree age (yrs.)	DBH (cm)	Height (m)	Volume / tree (m3)	Target N° of trees	Total volume (m3)	Volume / lumber (m3)	N° of lumbers	Local market Price / m3 ($)	Income / tree ($)	Total income ($) USD	Total income FCFA
10	25	20	0.33	1000	4,125	0.036 (MINFOF)	114,583	245.50	81.02	81,020	45,263,443
15	37.5	30	1.10		13,750		381,944		270.05	270,050	150,868,834
20	50	40	2.26		28,250		784,722		554.83	554,830	309,966,876

 

The above values assume local market price stays the same and that all trees are planted, grow and mature in time.

 

 

Sawn 36-year-old tree shows no sign of parasite attacks – Treff-End & Wewuley Consultancy joint research activities on Cedrela mexicana species – Moyuka, May 2017

 

Conclusions:

•  The environmental conditions in Woteva village match those of the species’ ideal growth conditions. This indicates that Woteva village is favourable for growing this species. These environmental conditions in Woteva village are relatively similar to other surrounding mountainous foothill villages and regions. Hence, the trees can be grown in other surrounding areas as well.
• The recorded average DBH and height in the demonstration farms is higher than values attributed to this species by most researchers. This indicates that the trees will grow faster in Woteva village and surrounding mountainous foothill regions. However, values from the 36-year-old trees suggest that trees grow faster during their early growth stages, but this rapid growth slows down when trees have neared their maximum heights. However, after 40 years, the wood volume per tree will be slightly above the standard estimate values.
• This species can provide a faster reforestation alternative in some areas of the mountainous regions were local species are extinct.
• Given the rapid growth rates of trees and the importance of the wood for local market consumption, this species can become an important economic asset to villagers on the foot of Mount Cameroun which should not be neglected. 

 

Therefore, Woteva and other villages on the foot of Mount Cameroon can grow Cedrela species as a means to rapidly regenerate the forest and to diversify opportunities for sustainable development.

 

Recommendations:

1. Cedrela species should in no way be used to replace local tree species. Instead, Cedrela trees should be grown together with local tree species. Not only will local vegetation be preserved, the new species will accelerate the regeneration of the forest and lead to other potential sustainable development projects.
2. Given its potential invasive nature, care should be taken to engage in proper tree control mechanisms after planting this species.
3. In Latin America, the tree is grown together with species such as Mahogany and Eucalyptus to avoid large pest population build-up. On the foothills of Mount Cameroon, agroforestry will provide a better alternative not only to prevent any large pest population build-up but also to ensure a diversified and maximum use of the land.
4. Cedrela species produce flowers after nine to fifteen years. These flowers are a good source of nectar for honey bees. If villagers living in these mountainous regions plant this species, they will have the possibility to develop profitable honey farms.

 

References:

• Krejcie, Robert V., and Daryle W. Morgan. “Determining sample size for research activities.” Educational and psychological measurement3 (1970): 607-610.
• Lescuyer, Guillaume, et al. “National demand for sawnwood in Cameroon. A barrier to or an opportunity for promoting the use of timber resources of legal origin?.” (2017).
• Ministry of Forestry and Wildlife, Regional Service of Forestry, Non-objection for the recuperation of abandoned logs, October 14^th, 2015
• Cintron, Barbara B. “Cedrela odorata L. Cedro hembra, Spanish cedar.” Silvics of North America654 (1990): 250.
• JUANITA GARCIA-SAQUI, GROWTH RATE OF TECTONA GRANDIS AND CEDRELA ODORATA IN MONOCULTURE AND MIXED SPECIES SYSTEMS IN BELIZE, CENTRAL AMERICA, UNIVERSITY OF FLORIDA 2007.
• Ford, L. B. “An estimate of the yield of Cedrela odorata L.(Syn. C. mexicana Roem.) grown in accociation with coffee.” An estimate of the yield of Cedrela odorata L.(Syn. C. mexicana Roem.) grown in accociation with coffee.(1979): 177-183.
• MINISTRY OF FORESTRYAND WILDLIFE, THE MANAGEMENT PLAN OF THE MOUNT CAMEROON NATIONAL PARK AND ITS PERIPHERAL ZONE, 2015 – 2019, October, 2014.