





























1 

 

In ternationa l
Scholars
Journa ls

 

African Journal of Environmental Economics and Management ISSN 2375-0707 Vol. 10 (5), pp. 001-024, May, 
2022. Available online at www.internationalscholarsjournals.org © International Scholars Journals 

 

Author(s) retain the copyright of this article. 
 

 

Full Length Research Paper 

 

Impact of wood cuts on the structure and 
floristic diversity of vegetation in the peri-urban 

zone of Ngaoundere, Cameroon 

 
Tchobsala1*, Amougou Akoa2 and Mbolo Marie2

 
 

1
Faculty of Sciences, University of Ngaoundere, Box 454, Cameroon. 
2
Faculty of Sciences, University of Yaounde, Box 812, Cameroon. 

 
Accepted September, 2021 

 
The main objective of this paper was to study the impact of various wood cuts on the structure and the 
floristic diversity of the savannas, and to seek for durable solutions against deforestation during a four 
year investigation. An inventory of the woody layer on 120 sites areas of 50 × 50 m showed that 
savannas have structures in "L". This structure translate the state of the degradation of the vegetation. 
The floristic diversity showed that the characteristic species of the degradation of the shrubby 
savannas area are Hymenocardia acida, Piliostigma thonningii and Annona senegalensis, and those of 
the wooded savannas are Daniellia oliveri and Cesalpinia sp. It was also shown that highest wood cuts 
are depressive for the stability of the savannas and for the disappearance of the vegetable biodiversity. 
Consequently, they are responsible for the acceleration of the degradation and the alarming installation 
of the desert in wet savannas of Ngaoundéré. A measure of co-administration between the government 
and the bordering population must be therefore encouraged to protect and safeguard the anthropized 
vegetation. 

 
Key words: Wood cuts, structure, floristic diversity, degradation, reconstitution, Cameroon. 

 
INTRODUCTION 

 
The impact of wood cuts on African savannas became 
increasingly extensive since a quarter century, accele-
rating therefore the degradation of the natural resources 
(Ndjidda, 2001). The satellite pictures of occupied 
grounds in the the wet savannas of the Adamaoua’s 
region in Cameroon showed that the surface passed from 
120 ha in 1951 to 1256 ha in 2001, that is, a mean rate of 
increase of 22 ha per year. This surface would be 1454 
ha in 2010 by extrapolation. The surface of shrubby 
savannas decreased approximately 10.8% compared to 
the year 1951 due to the creation of vast fields of corn 
production in the North of Ngaoundéré; a major city 
located in that region, the appearance of a significant 
agriculture in the South of the city, the plantations of the 
corn mill company occupying 1548 ha. The galleries  
 
 
 
*Corresponding author.  E-mail:  tchobsala2002@yahoo.fr.  Tel: 
74248541/96050865. 

 
 
 

 
along the roads and near villages are the most cut by the 
population (Tchotsoua, 2006).  

Their surfaces passed from 1844 to 784 ha between 
1951 and 2001; that is, a reduction of more than 50%. 
Rippstein (1985), Yonkeu (1993) and Tchotsoua (2005) 
worked on the degradation of the wet savannas of 
Adamaoua by overgrazing, overpopulation, agriculture, 
and exploitation of woods for cooking by the local 
population. In North Cameroon, Ntoupka (1994, 1998) 
investigated the regression of the forest by the combined 
effects of wood cuts, bush fire and overgrazing. Mbolo 
(2005), Zapfack (2005), Guedje (2002) and Sonké (1998) 
worked on the impact of wood cuts on the structure and 
floristic diversity in South Cameroon’s vegetation. These 
studies showed that wood cuts significantly affect the 
structure and floristic diversity of vegetation. But in the 
wet savannas of Ngaoundéré, no work is yet carried out 
on the impact of wood cuts on the structure and floristic 
diversity of the vegetation, except that of Chouaibou 
(2006) who worked on the structure of Parkia biglobosa 



2 

 

 
 
 

 

in the district of Ngaoundéré. However that area is among 
those seriously threatened by anthropic activities (wood 
cuts, bush fire, overgrazing, etc.).  

This study will be devoted to the impact of different 
wood cuts on the structure and floristic diversity of 
vegatation in general, and specifically to the modification 
of the structure of the vegetation, floristic diversity, and 
methods of conservation of the vegetables. 
 

 

Description of the study area 

 

The study was conducted in the subdivision of 
Ngaoundéré including ten villages namely: Béka 
Hooseré, Wakwa, Tizon, Beskewal, Ngaohora, Borongo, 
Dang, Onaref, Darang and Mbang- Mboum (Figure 1). 
The choice of these villages was related to their proximity 
to the capital of the Adamaoua region (Ngaoundéré), and 
to the regional weather station. They are located in an 
aureole of approximately 900 m² around Ngaoundéré 
(7°14'N, 13°34'E) except Mbang-Mboum, located some 
60 km far away. In 2001, the population of Ngaoundéré 
was approximately 230 000 inhabitants, with a rate of 
increase of 2.81% (Tchotsoua, 2006). The main activities 
are breeding and agriculture. More than 53% of the rural 
population practises traditional agriculture of subsistence 
(millet, cassava, sorghum, potato, corn, yam, groundnut, 
tomato, etc). The area, however knew an industrial crop 
in the years 1970 with the creation of some agro-
alimentary firms. The grounds are characterized by 
sedimentary, volcanic, granitic, and metamorphic rocks, 
including: Tropical ferruginous ferralitic grounds (Humbel, 
1971); modal slightly ferralitic grounds (Martin and 
Segalens, 1966); luvisol and ferrisol, telvic or acrisols and 
nitosols grounds which develop on old basalts and 
occupy the major part of the plate; typical strongly 
unsaturated grounds with pseudo particles; altered 
ferralitic grounds; mineral rough grounds (lithosols and 
rankers) (Humbel, 1971); etc.  

The vegetation of the region of Adamaoua corresponds 
to a typical soudano-guinean sector with an active aspect 
from shrubby to raised savannas. These savannas are 
dominated by Daniellia oliveri and Lophira lanceolata 
(Létouzey, 1968, 1986), species that are prolific with the 
favour of the zooanthropic factors like farming fires, 
pastures and clearings. In the fallow and around the 
villages, this formation has the same aspect with an 
herbaceous layer dominated by many andropogoneas 
(Hyparrhenia spp., Andropogon spp. …) and paniceas 
(Panicum spp....) which can reach at the end of the 
 
vegetative cycle up to 2 to 3 m in these zones. Abundant 
precipitations occur between June and August, and are 
null from November to February. The atmospheric 
relative humidity is maximum in August with a monthly 
average of 81.38%. The maximum monthly average for 
the rainy season varies from 68.32% (April) to 81.8% 
(August) while the minimal for season is between 3.12% 
(February) and 6.3% (November). The population mainly 

 
 
 
 

 

uses Hymenocardia acida, Piliostigma thonningii, 
Terminalia glaucescens, Guineense Syzygium spp, L. 
lanceolata, Harungana madagascariensis and Annona  
senegalensis etc, as cooking energy, Terminalia 
macroptera, Terminalia glaucscens, Lophira lanceolata 
and Sysygium guineenses VAr macrocarpum etc for coal, 
Vitellaria paradoxa, Tamarindus indica, Syzygium 
guineense, Ximenia americana as comestible wild fruits 
(Tchosoua et al., 2000 and Mapongmetsem, 2005), 
Piliostigma thonningii as forage for the ruminants during 
dry seasons (Tchobsala, 2003), D. oliveri, T. 
glaucescens, T. will macroptera, Terminalia laxiflora and 
Uapaca togoesis for wood service, and D. oliveri and X. 
americana for bee-keeping. 

 

MATERIALS AND METHODS 
 
Choice of the different wood cuts in the savannas 
 
To determine the degree of wood cuts, the method of “Quadrants 
Centered on a Point" was used. 200 plants were therefore chosen 
on areas of 2500 m² and the sites grouped according to their 
degrees of wood cuts. Sequences from 0 to 10%; 11 to 25%; 26 to 
50%, and 51 to 100% were retained for the study. The choice of 
sites took into account the access to the wooden resource and the 
distance from the village (0 to 0.5 km; 0.5 to 1 km; 1 to 2 km; 2 to 4 
km; 4 to 6 km and > 6 km).  

Percentages of wood cuts permitted to determine four types of 
wood cuts (treatments) in the peri-urban zone of Ngaoundéré are: 
 
1. Pilot or witness cuts (T0): Made up with natural formation where 
the percentage of wood cuts is less or equal to 10%. These are 
generally protected areas.  
2. Weak cuts (T1): Vegetation where the percentage of wood cuts 
is between 11 and 25%.  
3. Average cuts (T2): Where the percentage of wood cuts is 
between 26 and 50%.  
4. Complete or total cuts (T3): Vegetation where more than 50% of 
woods are cut. 

 

Experimental device 
 
The experimental device installed in 2004 was a split-study with 3 
factors (shrubby savannas, raised savannas and wooded 
savannas) (Table 1). The pieces were numbered from 1 to 12, 
delimitated by numbered cement terminals or wood stakes. 30 sites 
were selected for each treatment; that is 120 sites in total (3 types 
of savannas × 4 types of cuts × 10 villages). A compass was used 
for a good orientation on the study area 

 

Methods of data collection and analysis of vegetation 
 
The heights and diameters of the vegetation were measured by a 
team of five persons: The pointer, three assistants and a guide who 
plays the role of coordinator and monitor. The team sweeps each 
tailboard of 50 × 50 m one after the other. The species are identified 
in local language by the guides and thereafter compared to those of 
the herbaria of Wakwa (Adamaoua) and the schools of fauna of 
Garoua and Yaounde. The species that were not identified in these 
herbaria are sent in the National Museum of Natural History of the 
Institution Smithsonian and Missouri Botanical Garden in the United 
States of America.  

The readings of the vertical stratification were taken in the 



3 

 

   
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

 
Figure 1. Study area. 



4 

 

            

 Table 1. Experimental device.         
              

   N° Bes Beka ONA Bor Wak Tiz Nga Dar Dan Mba 

 1 SaT3 SaT3 SaT2 SaT3 ScT0 SaT0 SaT3 SbT0 ScT1 ScT0 

 2 SaT2 SaT2 SaT3 ScT3 ScT3 SaT1 SaT2 SaT0 ScT2 SaT0 

 3 ScT3 SaT0 ScT0 SbT1 ScT2 SaT2 SaT1 SaT1 ScT3 SbT0 

 4 ScT2 ScT0 ScT3 ScT2 SbT1 SaT0 SaT0 ScT0 ScT0 SbT2 

 5 SbT1 SbT3 SaT0 SaT1 SbT0 SbT1 SbT0 SaT2 SaT0 SbT3 

 6 SbT3 SbT2 SbT0 SbT0 SbT2 SbT0 SbT2 SaT3 SaT2 SbT1 

 7 SbT0 SbT0 SbT3 SbT3 SaT1 SbT3 SbT1 ScT3 SaT1 SaT3 

 8 SaT0 ScT1 SbT1 ScT0 SaT2 SbT3 SbT3 SbT3 SaT3 SaT2 

 9 ScT0 ScT3 ScT1 SaT0 SaT0 ScT3 ScT3 SbT2 SbT3 SaT1 

 10 SaT1 ScT2 ScT2 ScT1 SbT3 ScT2 ScT2 SbT1 SbT0 ScT3 

 11 SbT2 SaT1 SbT2 SaT2 SaT3 ScT1 SbT1 ScT2 SbT2 ScT2 

  12 ScT1 SbT1 SaT1 SbT2 ScT1 ScT0 ScT0 ScT1 SbT1 ScT1 
 

Bes: Beskewal; Bek: Beka; ONA: ONAREF; Bor: Borongo; Wak: Wakwa; Tiz: Tizon; Nga: Ngaouhoura; Dar: Darang; Dan: Dang; Mba:  
Mbang-Mboum; Sa: shrubby savannas; Sb: Raised savannas; Sc: wooded savannas. 

 

 

heights’ sequences of: 0-50 cm; 50-130 cm; 130-200 cm; 200-400 
cm; 400-600 cm; 600-800 cm; 800-1000 cm; 1000-1200 cm; 1200-
1400 cm; 1400-1600 cm; 1600-1800 cm, 1800-2000 cm, 2000-2500 
cm and >2500 cm. The measurements of the horizontal 
stratification related to the diameters of the trees were taken 
according to the following sequences: 0-5 cm; 5-10 cm; 10-15 cm; 
15-20 cm; 20-25 cm; 25-30 cm; 30-35 cm; 35-40 cm; 40-50 cm; 50-  
60 cm; 60-80 cm; 80-100c m; 100-120 cm, 120-150 cm, 150-200 
cm, 200-250 cm and > 250 cm.  

The heights were measured on all alive and cut species on areas 
of 50 x 50 m² according to a cross or linear transect in each village. 
For highest trees with more than two meters, a clinometer was 
used. The numbers of cut and alive trees were taken to evaluate 
the death rate of the flora per unit of area. Measurements of the 
circumferences at heights of 1.30 cm were taken to evaluate the cut 
susceptibility of the species. The woody cover of each species was 
measured starting from the surface of projection of the foliages on 
the ground using a decametre. The measurements of natural 
regeneration were taken on the seedlings heights less or equal to  
50 cm from the ground in the rainy season (Tchobsala, 2003). 

The analysis of the results was done by several methods: 

 
1. The profile of stratification suggested by Amougou (1986) for 
tropical areas was adopted: 

 
a. Layer A or higher arborescent layer, made up with very high 
trees (35 m and more);  
b. Layer B or average arborescent layer, whose heigths are 
between 25-35 m, forming a more or less continuous and dense 
canopea;  
c. Layer C or lower arborescent layer, constituted with 15-25 m 
heights trees;  
d. The layer D or shrubby layer, made up with small trees and 
shrubs less than 15 m height. 
 
For these arborescent layers, it was necessary to add the 
herbaceous layer or layer E which can reach 3 m height, constituted 
of epiphytes and lianas.  

The combination of these 4 layers offers 15 types of stratification 
with a single possibility of complete stratification, 4 possibilities with 
3 layers, 6 to 2 layers and 4 mono-stratified possibilities. Moreover, 
each one of these layers can be subdivided into sub-layers which 
are indicated from the top to the bottom by numbers 1, 2 and 3 
affected by letters indicating the layers. For example, a sub-layer D 

 
 

 
can be presented as follows: 
 
D1: 10-15 m, small trees;  
D2: 5-10 m, shrubs; 
D3: 5 m and less, shrubs or suffruteux. 
 
2. Richness of the settlement: It corresponds to the relationship 
between the number of individuals and species;  
3. The index of diversity of Shannon (1949) in Legendre and 
Legendre (1984) is given by: 
 

ISH = - ∑(Ni/N) log2 (Ni/N) 
 
where Ni is the number of species i and N the total number of the 
species.  
3. Equitability (EQ) of Piélou in Frontier and Pichod-Viale (1993) 
is given by: 
 

EQ = ISH/log2N. 
 
It corresponds to the relationship between the observed diversity 
and the maximum possible diversity of the number of species N.  
4. The index of diversity of Simpon is given by: 

D = 1/∑ (Ni/N) 
2
 (Begon et al., 1987) 

 
or simply 
 

D = ∑ (Ni/N) 
2
 (Colinvaux cit.Sonké, 1998). 

 
5. The absolute density (Ni) of a taxon corresponds to the total 
number of the stems of this taxon per unit of area.  
6. The relative density (Dr.) is the relationship between the number 
of individuals of a species and the total number of individuals of all 
the species met on an area multiplied by 100.  
7. Terrian surface (St) of species i is the sum of the terrian surfaces 
of all representant of the species.  
8. The relative predominance (Pr.) of species i is the ratio of its 
terrian surface to the total terrian surface of the settlement  
10. The absolute frequency (F) of species i is the number of 
statement containing this species.  
11. The relative frequency is the number of the statements 
containing this species to the total number of the statements 
multiplied by 100. According to Braun- Blanquet (1932), the indices 



5 

 

      

Table  2. Indices of relative frequency.     
       

  Symbols Indices Type of death   

  I 0- 20 Accidental species  

  II 21-40 Additional species  

  III 41-60 Rather frequent species  

  IV 61-80 Frequent species  

  V 81-100 Very frequent species   
 

 
Table 3. Delimitation of the layers according to the maximum diameter reached.  

 
Categories of species Diameter Category   
Arborescent species  
Large (wooded savannas)  
Averages (raised savannas)  
Small (raised savannas) 

 
Shrubby species  
Large (shrubby savanna)  
Averages (shrubby savanna)  
Small (shrubby savanna) 

  
 

100 cm exceed A 

Ranging between 50 and 100 cm B 

Ranging between 20 and 50 cm C 

Ranging between 10 and 20 cm D 

Ranging between 3 and 10 cm E 

Ranging between 0 and 3 cm F  
 

 

of this frequency is summarized in Table 2. The delimitation of the 
layers was made on the basis of maximum diameter reached (Table 
3), using the scale of Letouzey (1986) and Volter (1993), and 
making some modifications to the various categories of species. 
The species were classified in two groups (arborescent and 
shrubby) and, various categories were retained within these groups.  
12. The principal phytogeographical types are those admitted for 
Africa (Lebrun, 1947). The recognized types are the species with 
broad geographical distribution including: 
 
a. Cosmopolitans (Cos): Species found throughout the whole world;  
b. Pantropicales (Pan): Species known in Africa; 
c. Tropical-American and Asian;  
d. Afro American (AA): Species extended in tropical Africa and 
America;  
e. Paleotropical (Pal): Species present in Africa and tropical 
Asia, Madagascar and Australia;  
f. Afromalgaches (AM): Species common to the islands of 
Madagascan and central African areas;  
g. Multi-regional African (PRA): Species whose surface of 
distribution covers several floristic African areas or two floristic 
areas which are not in contact.  
We also have guineean and soudano zambezian species (G-sz) 
species including: 

 
a. Sub-Omni guineo-congolese (GC): Species presented in all the 
floristic guinean area;  
b. Central (CG): Species whose surface of distribution goes from 
Cameroon to the Democratic Republic of Congo;  
c. Western guineans (WG): Species which are widespread of 
Western Africa in Western Cameroon;  
d. Cameroon-Congo (CaCo): Species only found in the 
Cameroonian solid mass and the Congolese basin;  
e. Cameroon-Gabon (Ca-Gab): known species only of the forest 
solid mass Cameroon-Gabon-Mayumbe.  
f. Cameroon (Camwood): Species only found in Cameroon. 
 
13. According to Lebrun (1947), the biological type of a species is 

 

 

the whole of the anatomical and morphological devices which 
characterize its vegetative apparatus and make conspicuous its 
habitat and its aspect independently to its systematic position and 
adaptation to the environmental conditions. Biological types 
according to the classification of Raunkiaer (1934), adapted to the 
tropical areas by Schnell (1971) are: 
 
a. Phanerophytes including: 

 
i. Megaphanerophytes (MgPh), whose heights are around 30 m;  
ii. Mesophanerophytes (MsPh), whose heights range between 10 to 
30 m;  
iii. Microphanerophytes (McPh) , whose heights range between 2 to 
10 m;  
iv. Nanophanerophytes (NnPh), shrubs with heigths under 0.4 to 2 
m.  
v. Phaneorophytes lianescents (Phgrv. Phgr); voluble plants with 
gimlets, cramps roots, crawling or supported;  
vi. Phaneorophytes epiphytes (Phep). 
 
b. Chameophyts (CH): 
 
i. Chameophytes drawn up (Chd);  
ii. Chameophytes prostrate (Chpr); 
iii. Chameophytes crawling (Chrp);  
iv. Chameophytes climbing (Chgr); 

 
c. Geophytes (G): Plants whose persistent growths or buds are 
sheltered in the ground during the bad season: 
 
i. Rhizomateux geophytes (Grh); 
ii. Tuberaux geophytes (GB);  
iii. Geophytes climbing (Ggr); 
iv. Geophytes epiphytes (Gep). 
 
d. Hemicryptophytes (H): plants which the growths are located at  
the short-nap cloth of the ground: 
* Cespiteux Hemicryhytes (Hce). 



6 

 

  
 
 
 
 
 

 1600 
 

 1400 
 

-1
 1200 

 

 
 

o
fs

t

e
m

s
.h

a
 

1000  
 

 

 800 
 

N
u

m
b
e

r 

600 
 

400  
 

 

 200 
  
0 

 
 
 
 
 
 
 
 
 
 
 
 

 
Shrubby savanna  
Raised savanna  
Wooded savanna  

 

0-50
 200-400 800-1000 1600-1800 

> 2500
 

 
Heights (cm) 

 
Figure 2. Structure of the population according to the size of the trees. 

 

 
e. Theophytes (Th): Annual plants or at very short growing period, 
deprived of persistent buds themselves and whose survival is 
ensured by seeds, they include: 
 
i. Theophytes drawn up (Thd); 
ii. Theophytes prostrate (Thpr);  
iii. Théophytes scapeux (Thsc). 
 
f. Hydrophytes (Hy); watery plants.  
In this work, we interested only to the megaphanerophytes, 
mesophanerophytes and microphanerophytes. Trees which have 
less than 10 cm diameter to height of the chest were exclusively 
inventoried. 
 
14. The types of dissemination of diaspores were given according 
to the classification of Dansereau and Lems (1957). The various 
types are: 

 
a. Pterochores (Ptéro): Small diaspores with aliform appendices;  
b. Pogonochores (Pogo): Diaspores with feathery or silky 
appendices;  
c. Slerochores (Scléro): Not fleshy and relatively light diaspores; 
d. Sarcochores (Sarco): Diaspores completely or partially fleshy;  
e. Desmochores (Desmo): Diaspores hanging or adhesive; 
f. Ballochores (Ballo): Diaspores expelled by the same plants; 
g. Barrochores (Baro): Not fleshy diaspores;  
h. Pleochores (Pleo): Small diapores with a floating appendix. 
 
15. StatBox version 6.40 was used for the factorial analysis of the 
principal components (ACP) of the structure of the vegetation. 

 

RESULTS 
 
Structure of the vegetation according to the various 
types of vegetable formations 
 

The structure of the vegetation as a function of the types 
of savannas is presented in Figure 2. It is seen that in 
general, cut savannas have structures in "L", materialized 
by a great number of minor stems and little adult stems. 
Such a structure generally presents a good arborescent 

 
 

 

regeneration after wood cuts. The curve of tendency 
presents an equation of the form y = -2601.2 x + 25300 
with a coefficient of correlation of 0.5249. The number of 
the stems is more significant in shrubby savannas with 
vegetables’ heights between 0 and 200 cm. In the three 
types of formations, there is a reduction in the number of 
stems when the size of trees increases. From 200 cm the 
number of stems is almost null. 
 

 

Structure of savannas according to the various types 
of wood cuts 

 

The structure of the vegetation in the treatments T0, T1, 
T2 and T3 is presented in Figure 3. It can be seen that in 
some type of savannas, the number of stems is 
significant between 0 and 200 cm (T0). Shrubby and 
wooded savannas are more representative in the number 
of stems. Raised savannas are richer in stems of 
vegetables with heights between 0 and 130 cm for the 
treatment T1. The number of the stems decreases when 
the heights of the trees increase. From 200 cm, the 
number of the stems becomes null. In fairly cut savannas 
(T2), the trees have more significant stems in wooded 
savannas where trees’ heights are between 0 and 130 
cm while highly cut savannas (T3) present less stems. 
From 200 cm, few trees are found. In general, the 
vegetation consists in young plants resulting from the 
regeneration of the cut trees. It is at the level of shrubby 
savannas that the number of rejections is significant  
 

 
Impact of wood cuts on the evolution of the structure 
of savannas from 2004 to 2006 
 
The structure of the vegetation from 2004 and 2006 
presented a light regressive evolution (Figure 4). The 



7 

 

  
 

 

500 
   400   

 

  

(a) 350 
  

 

    (b)  

400 
   

300 
 

 

     
 

300    250   
 

       

    200   
 

200    150   
 

      
 

100    100   
 

0 
   50   

 

  

1600-1800 0 
  

 

0-50 200-400 800-1000   
 

Classes of heights of stems ha
-1

 in cm 0-50 200-400 800-1000   1600-1800 
  

Classes of heights of stems ha
-1

 in cm  
 
 

 

N
u
m

b
e
r 

o
f 
s
te

m
s
 h

a
-1
 

 
 
 

     800     
 

600    

-1
      

 

    700     
 

    

h a
     

 

500       
(d) 

 
 

  
(c) 

 of
st

em
s 

600    
 

400 
       

 

         

    500     
 

         
 

300    
N

u
m

b
e

r 
400     

 

200 
   300     

 

         

         
 

     200     
 

100     
100     

 

         
 

0     0     
 

   

>2500      
 

0-50 400-600 1200-1400  

0-50 200-400 800-1000 1600-1800 >2500    
 

     
 

 Classes of heights of stems ha
-1

     -1 -  
 

      Classes of heights of stems ha (cm)  
  

 
 

Shrubby savanna Raised savanna Wooded savanna  
 

Figure 3. Structure of savannas according to the cuts: (a), weak (b), average (c) and strong (d). 
 
 

 
 4500       

 

-1
 

4000 
      

 

h a
       

 

       
 

st
e

m
s 

3500       
 

        

 3000       
 

of
th

e 2000      2004 
 

     2006  

d
e
n
s
it
y

 

2500       
 

1500       
 

        

A
bs

ol
ut

e 

1000      

>2500 
 

500 130-200 400-600 800-1000 1200-1400  
 

        

  0      
 

 0-50     1800-2000  
  

 
Figure 4. Evolution of the vertical structure of the vegetation of 2004 to 2006. 

 
 

 

number of the stems decreased gradually from 2004 to 
2006. This translates the regression of the wet savannas 
of Ngaoundéré. The curve of evolution of the stems by 
hectare decreased brutally from the heights 0 - 50 cm to 
400 - 600 cm. From 600 up to 2500 cm, the curve is 
superimposed on the x-coordinate. It can be seen from 
the graph that the structure of the heights is represented 

 
 
 

 

by the curve in "L ". 
 

 

Diametric structure of the ligneous family 

 
The classes of trees with diameters from 0 to 10 and 10 
to 20 cm present highest number of stems (Figure 5). In 



8 

 

  
 
 
 
 
 
 

 

N
 u

m
 b

e
r 

o
f 
s
te

 m
 s

 /
h
a
 

 
 
 

 
60000 

 
50000 
 

 Shrubby savanna  
40000  

 Raised savanna 
 
30000 

Wooded savanna 
 
20000 

 
10000 

 
0  

010-20  30-40 50-60 70-80 90-100 110-120130-140 170-180 190- 
 

 
Classes of diameters in cm 

 
Figure 5. Diametric structure of the ligneous family in savannas of the cuts. 

 
 
 

2D Graph 2  

 
 25000 

 20000 

 15000 

D
a
ta

 

10000 

Y
 

 

 5000 

 0 
 

 
T0a T1a T2a T3a T0b T1b T2b T3b T0c T1c T2c T3c 
 

X Data 
 

Plot 1 

 
Figure 6. Diametric structure of the ligneous family as a function of various 
wood cuts. T0a: treatment T0 shrubby savanna;T1a treatment T1 shrubby 
savanna; T2a treatment T2 shrubby savanna; T3a treatment T3 shrubby 
savanna; T0b treatment T0 raised savanna; T1b treatment T1 raised savanna; 
T2b treatment T2 raised savanna; T3b treatment T3 raised savanna; T0c 
treatment T0 wooded savanna; T1c treatment T1 wooded savanna; T2c 
treatment T2 wooded savanna; T3c treatment T3 wooded savanna 

 

 

these classes, highest number of rejects are found. 
 

 
Diametric structure of the vegetation according to the 
various wood cuts 

 

The treatment T0a presents the greatest number of the 

 
 

 

individuals, followed by T1a and T2a. The others are 
almost equal in density of individuals (Figure 6). The 
analysis of principal component (ACP) shows that the 
values of Pearson are significant (except diagonal) for the 
threshold alpha = 0.05 (bilateral test). This shows that the 
structure of the vegetation varies according to the classes 
of the diameters of the stems. The highest average is for 



9 

 

  
 
 

 
Table 4. Average and standard deviations of the diametric structure of the woody state.  

 
 Classes of diameters in cm Average Standard deviations 

 0-10 A 10735.50 5348.62 

 10-20 B 9592.75 2637.72 

 20-30 C 3902.75 2527.11 

 30-40 D 796.67 245.51 

 40-50 E 218.25 90.32 

 50-60 F 76.67 44.18 

 60-70 G 43.67 30.81 

 70-80 I 28.17 21.95 

 80-90 J 28.50 22.40 

 90-100 K 6.58 5.87 

 100-110 L 2.83 2.85 

 110-120 M 1.50 1.98 

 120-130 N 1.58 2.33 

 130-140 Q 2.75 6.03 

 140-150 U 3.08 6.49 

 150-160 S 3.75 9.57 

 160-170 V 1.83 3.34 

 170-180 W 0.58 0.86 

 180-190 X 0.42 0.76 

 190 -200 Y 0.42 1.11 

 >200 Z 0.33 0.62 
 
 
 

 
the class of diameters between 0-10 cm (10735.50 

stemsha
-1

year
-1

) with a standard deviation equals to 
5348.62. The lowest average is obtained for the class of 
diameters greater than 200 cm (Table 4).  

The analysis of the principal variables component, 
according to the axes F1 and F2 shows a variation of 
57% in the classes of diameters (Figure 7). The classes 
A, B and C are under the axis, the others are gathered 
around similar values (variable (axes F1 and F3) 53%, 
variables (axes F1 and F4) 46%, variables (axes F2 and 
F3) 38%, variables (axes F2 and F4) 31%, variables 
(axes F and F4) 27%). 
 

 

Classification of the species according to the 
maximum diameter 

 

The species were classified depending on the diameters 
reached. In the wet savannas of Ngaoundéré, a great 
number of stems has diameters between 0-10 cm (Table 
5). H. acida, H. madagascariensis, P. thonningii, Annona 
senegalinsis etc are mainly found. The density of these 
stems decreases as the diameter increases. When the 
diameter is beyond 100 cm, there is no stem in the 
shrubby savannas. In addition, the density remains 
significant for wooded savannas and form forest galleries 
of high trees. In this class, D. oliveri, Cesalpinia sp., Z. 
guiennese VAr. guinense, T. glaucescens, L. lanceolata, 

 
 
 
 
etc. are found. 
 

 

Influence of wood cuts on the survival and the 
biological state of the species as a function of each 
type of vegetable formation 

 

Figure 8 presents the effects of wood cuts on the density 
of alive and dead stems in the three types of vegetable 
formations. In the shrubby savannas, treatment T1 
presents the greatest number of alive stems, while much 
of cut stems are found in T3. In raised savannas, the 
number of the cut stems is more significant. However, the 
numbers of cut stems are approximately the same in the 
four treatments. In wooded savannas, the numbers of 
alive stems are approximately the same for T0 and T2. 
They are relatively less in T1 and T3. The number of the 
cut stems is very weak for the whole treatments. 
 

 

Influence of various types of wood cuts on the 
biological state of the vegetation 

 

Figure 9 summarizes the impact of the wood cuts on the 
density of the stems as a function of the treatments. For 
the treatment T0, the density of alive stems is significant 
in the shrubby and wooded savannas, but it is less in 
raised savannas. The numbers of cut stems decrease in 



10 

 

   
 
 

 
Variables (axes F3 and F4 : 27%) Variables (axes F1 and F2 : 57%)  

 
 

 
 
 
 
 
 
 

--
a
x
e

  
F

4
 (

1
0
%

)

 

  
 

1.5       
 

1       
 

  C     
 

0.5 
 B D    

 

     
 

  A    
 

      
 

  I
 FGE 

SQ V 
X Z 

  
 

0 
 U   

 

   W 
Y 

 
 

  
J M N  

 

      
 

-0.5  L
K
     

 

      
 

-1       
 

-1.5       
 

-1.5 -1 -0.5 0 0.5 1 1.5 
  

a --axe F3 (17%) 
 

 
 

   

 
 
 
 
 
 

 

--
a
x
e
  

F
2

 (
2

1
%

) 

  
 

1.5       
 

1    S
UQ 

  
 

      
 

    V   
 

0.5       
 

     G 
 

0 
    I F  

 

    J E  

    

LDK 
 

      
 

  A B   C Y W  
 

     

    X  
 

-0.5     ZNM  
 

      
 

-1       
 

-1.5       
 

-1.5 -1 -0.5 0 0.5  1 
 

b  --axe F1 (36%)    
 

     
  

 
Figure 7. Variation between the classes of diameters of the vegetation of Ngaoundéré. 

 

 
Table 5. Classification of the species according to the diameters reached.  

 
Diameter (cm) Categories Shrubby Savanna Raised savanna Wooded savanna 

0-10 E et F 1852 1256 1186 

10-20 D 1430 1247 1160 

20-50 C 736 490 741 

50-100 B 6 30 138 

>100 A 0 10 76 
 
 

 

the shrubby and wooded savannas. They are very weak 
in protected savannas, showing that in the protected 
savannas, the activity from the exploitation of wood 
resources is controlled. For slightly cut savannas (T1), 
the number of alive stems is relatively significant in raised 
savannas. For the treatment T2, the number of alive 
stems is very high in wooded savannas. Treatment T3 
presents a great number of alive and cut stems. This 
number falls when one passes from shrubby to wooded 
savannas. 
 

 

Impact of wood cuts on the evolution of the density 
of species from 2004 to 2006 

 
The vegetation is mainly made up of shrubs e.g H. acida, 
P. thonningii and H. madagascariensis which respectively 

had absolute densities of 3077, 1025 and 1542 stems.ha
-
  

1 in 2004; and 2907, 949 and 1511 stems.ha
-1

 in 2006. 
The relative densities of these species were respectively 
27.63, 9.21 and 6.021% in 2004. In 2006, there was a

 

 
 

 

light reduction in the relative density: 27.53, 8.99 and 
6.023% respectively, for these species. The difference 
between the relative densities of these species is not too 
perceptible because of their speed of regeneration. 
These three species clearly colonize shrubby savannas. 
Species like H. Madagascariensis, T. glaucescens and D. 
oliveri having relative densities of 13.851, 5.516 and 
5.421% in 2004 are forest species with affinity to 
Ngaoundéré’s region. Their relative densities also slightly 
increased in 2006, respectively 14.340, 5.746 and 
6.670%. They are more present in the forest galleries or 
wooded and raised savannas. Indeed, the species with 
forest affinity have a high capacity of regeneration 
towards threats. 
 

 
Impact of the wood cuts on the floristic composition 
and the density of the species 

 
140 species, 60 kinds, 34 families, and 371 alive 

stems.ha
-1

year
-1

 were averagely identified in 2004 and 



11 

 

  
 
 

 

  (a)   
 

-1
     

 

h a
 

900 
   

 

s
te

m
s
 

   
 

800    
 

700 
   

 

c
u
t    

 

600    
 

o
r    

 

500    
 

a
liv

e
 

400    
 

300    
 

o
f    

 

200 
   

 

N
u

m
b

e
r    

 

100    
 

0    
 

T0 T1 T2 T3 
 

 
  

 
 

 
 

  (b)  
 

- 1
    

 

N
u

m
b

e
r 

o
f 

a
liv

e
 o

r 
c
u

t 

s
te

m
s
 h

a
 

T1 T2 T3 
 

T0 
   

Type of the wood cuts     Type of the wood cuts 
 

Alive stems Cut stems 
 

    (c) 
 

1200         
 

1000 

        
 

         

        
 

800         
 

600         
 

400 

     

  Alive stems  

     
 

       
Cut stems 

 

        
 

200         
  

 
0   

T0 T1 T2 T3  
Type of wood cuts 

 
Figure 8. Density of the stems alive and cut in shrubby savannas (a), raised (b) and wooded (c). 

 
 

 

351 stems.ha
-1

 in 2006. The evolution of the specific 
density of the vegetation (Table 6) shows that the species 
which do not tolerate the wood cuts such as T. indica, 
Securidaca longepedunculata and Strychnos spinosa are 
disappearing in the savannas. In 2006, 13 new species 
appeared in the sites of study. This is the case of 
Erythrophleum guinneensis, Heeria pulcherima and Nuxia 
congesta. On the other hand, 25 species disappeared in 
2006.  

Among them T. indica, Combretum sp. and Croton sp. 
It could be noted that much of the species lost their 
density from 2004 to 2006 e.g. H. acida (170 stems.ha

-

1
year

-1
), P. thonningii (76 stems.ha

-1
year

-1
), A.  

senegalensis (35 stems.ha
-1

year
-1

) and H. 

madagascariensis (30 stems.ha
-1

year
-1

). Other species 
gained in density during these three years. Among them 
D. oliveri, Allophyllus africanus and Pachira aquatica.  

These results show that the degree of drageonment or 

 
 
 

 

the rejections of these species is very significant. 
 
 
Dynamics of the natural regeneration of the species 
according to savannas 

 

In the whole thirty hectares inventoried, shrubby 
savannas presented the highest capacity of regeneration 
(Figure 10). Raised and wooded savannas appreciably 
have the same densities of rejections per hectare.  

The average density of the rejections is 3712.45 
stems.ha

-1
 for individuals with circumference lower than 3 

cm, and 1423.41 stems.ha
-1

 for the individuals with 
circumference greater than 3 cm. 

 

Influences of wood cuts on natural regeneration 
 
Regeneration is more significant for the treatment T0 



12 

 

 
 
 
 
 

(a) Density of the stems according 
to the witness cuts (T0)   

1200   

- 1
   

h a
   

1000   

stems8
00   

o f   
600   

Number
s200   

400   

0   
Shrubby Raised Wooded 
savanna savanna savanna  
Types of savannas 

 
 
 

 
(b) Density of the stems according 

to the weak cuts (T1)  
 

1000  

- 1
 

 

h
a
 

800 

of
s

te m
s 

400 
 600 

N
um

be
rs

 

0 
 200 
 

Shrubby Raised 
savanna savanna Wooded 

savanna  
Types of savannas 

  
 (c) Density of the stems according to 

 

- average cuts (T2)  
 

h a
 

1200 
  

 

st
e

m
s   

 

1000   
 

    

o
f 800   

 

1   
 

N
um

be
r

s 

600   
 

400   
 

    

 200   
 

 0   
 

 Shrubby Raised Wooded 
 

 savanna savanna savanna 
 

 Type of savannas 
 

   Cut stems 
  

  
 (d) Density of the stems according to the 

 

-1
 high cuts (T3)  

 

h a
 

1600   
 

st
e

m
s   

 

1400   
 

   
 

 1200   
 

o
f 1000   

 1
 

  
 

N u m be rs
 

800   
 

200   
 

 600   
 

 400   
 

 0 
e 

 
 

 

Shrubby 
 

 

 Raised Wooded 
 

 savanna savanna savanna 
  

 
Type of savannas  

Alive stems 
 

 
Figure 9. Density of the stems according to the cuts: witness (a), weak (b), average (c) and high.  

 
 
 

 

N
u
m

b
e
r 

o
f 

re
g
e

n
e

ra
te

d
 s

te
m

s
 .

h
a

-1
 

 
 
 
 

 
2000 

 
1500 

 
1000 
 

500   

 

0   

 
 
 
 
 
 
 
 
 

 
Height  

 

Shrubby Raised Wooded 
Savanna Savanna Savanna 

 
Figure 10. Density of the seedlings according to savannas. 

 
-1

 
(391.933 stems.ha ) with a standard deviation of 

-1 
181.2306 stems.ha (Table 7). 
 

 

Evolution of the rejections after wood cuts 

 
The heights and the diameters of the seedlings were 
measured each year on pieces of 10 × 10 m cut at 

 
 
 

 

the level of the ground in order to study the dynamics of 
these species. It was observed that, some species 
integrated the parcel and others disappeared due to the 
pressure of the wood cuts. The height of each stem was 
measured each year during three years. During the first 
year, each rejection was marked, this made possible to 
evaluate the mortality of the stems. The mortality of the 
seedlings is in majority due to the activities of the 



13 

 

  
 
 
 

Table 6. Absolute density (stems ha
-1

) and relative and profit or loss of the ligneous family of the species (en %).  
 

  Absolute Relative Absolute Relative  Absolute Relative Absolute Relative 
 Scientifics names density density density density Scientifics names Density density Density density 

   2004 2006 2006   2004 2006 2006 

 Acacia polyacantha 14.47 0.13 12.47 0.12 V.  paradoxa 16.42 0 9.17 0 
 Acacia siberiana 0.47 0 0.07 0 Commiphora kerstengii 1.23 0.01 1.01 0 
 Afzelia africana 7.3 0 6.17 0 Cordia africana 0.12 0 0.1 0.01 
 Albizia chevalieri 0.83 0.01 0.8 0.01 Cordia myxa 0.01 0.01 0 0.02 
 Albizia coriaria 12.65 0.11 9.63 0.09 Cordia sinensis 0.63 13.85 0.61 14.34 
 Albizia lebbeck 4.63 0.04 4.63 0.04 Corianga sp 0.93 0.01 1.23 0.01 
 Albizia zygia 17.85 0.16 15.9 0.15 Crossopteryx febrifuga 0.14 0.83 0 0.83 
 Albizia adianthifolia 4.53 0.12 3.53 0.1 Croton macrostachys 92.18 0.01 88 0.01 
 Alchornea laxiflora 1.29 0 1.2 0 C. zambesicus 0.03 0.03 0.03 0.03 
 Allophyllus sp 46.55 0.42 66.47 0.63 Cussonia africanus 0 0 0 0 
 A. africanus 106.38 0.96 126.37 1.2 Cussonia barteri 40.65 0 39.83 0 
 Ancylobotrys amoena 0.07 0.14 0 0.13 D. oliveri 603.53 0.37 703.21 0.38 
 Andira inermis 0.07 0 0.03 0 Ekebergia senegalensis 8.5 5.42 9.5 6.67 
 A. senegalensis 670.48 6.02 635 6.02 Entada africana 312.67 0.08 300.5 0.09 
 Berlinia grandiflora 0.34 0 0 0 Erythrina senegalensis 3.11 0.29 3.07 0.23 
 Boswelia sp 0.11 0 0 0 Erythrina sigmoidea 235.4 0.02 213.14 0.02 
 Bridelia ferruginea 155.12 1.39 150.23 1.42 Erythrophlium guinense 238.48 2.81 2.5 2.85 
 Bridelia ndelensis 0.33 0 0.13 0 Espèces undeterminées 1.97 0.02 1.01 0.01 
 Burkea africanus 13.13 0.01 10.13 0.02 Eugenia nigerina 0.77 2.11 0.13 2.02 
 Carissa edulis 8.17 0.06 1.2 0 Ficus capreafolia 0.02 0.02 0 0.01 
 Carissa spanarum 13.5 0.07 10.5 0.01 Ficus vogelii 1.32 0.04 0.5 0.03 
 Cinera machrostachys 68.31 0 60.1 0 Ficus glumosa 28.85 0 18.53 0 
 Citrus sp 0.04 0.61 0.03 0.57 Ficus vallis-choudae 0.87 0.19 0.57 0.19 
 Clausena anisata 1.17 0 1.11 0 Ficus platiphylla 1.03 0 0 0 
 Combretum glutinosum 1.1 0.01 0.12 0.01 Ficus sp. 0.55 0.01 0.43 0 
 Combretum micrantha 26.05 0.02 25.9 0.01 Ficus sur 1.34 0.26 0.1 0.18 
 Combretum nigricans 0.02 0.07 0 0.06 Ficus sycomorus 8.43 0.01 8.3 0 
 Combretum molle 243.04 0.36 239.89 0.36 Ficus thonningii 2.25 0.01 1.13 0.01 
 Combretum lecardii 1.2 0.01 0 0 Ficus trichopoda 0.01 0 0.17 0 
 Flacourtia sp 0.13 0 0.13 0 Flacourtia indica 12.53 0.08 9.41 0.08 
 Flacourtia vogelii 0.07 0.01 0.02 0 Ochna Scheinfurthii 9.21 0.04 8.23 0.04 
 Flueggea virosa 0 0.75 0.02 0.78 Oncoba spinosa 2.07 0.47 1.07 0.48 
 Garcinia livingstonei 0.27 0.01 0.13 0.01 Ormocarpum bibracteatum… 0.04 0.47 0.09 0.47 



14 

 

            

 Table 6. Cont’d.          
            

  Gardena triacantha 11.71 0.01 11.63 0 P. aquatica 0 0.02 10.36 0.02 
  Gardenia aqualla 1.79 0 1.73 0 P. biglobosa 13.44 0.04 11.27 0.04 
  Gardenia ternifolia 4.57 0 2.53 0 Paullinia pinnata 0.13 0 0.11 0 
  Gmelina arborea 3.5 0.03 2.5 0.02 Persea americana 0 0 0.02 0 
  Grewia barteri 0.23 0 0.33 0 Phyllanthus muellerianus 50.51 0.06 48.9 0.07 
  Grewia bicolor 4.3 0.11 1.43 0.09 Phyllanthrus sp 0.03 0.08 0.03 0.08 
  Grewia flavescens 0.2 0.11 1.2 0.11 Phyllantus reticulatus 0.8 0.01 1.8 0.01 
  Grewia venusta 0.03 0.02 0.02 0.02 P. thonningii 1024.91 0.02 948.63 0.01 
  Grewia villosus 2.53 0.04 0 0.02 Platycerium stemaria 0 0.09 0.19 0.06 
  Gynocarpus americanus 0 0.02 0 0.01 Psidium guajava 5.8 0 6.17 0.05 
  H. madagascariensis 1542.2 0.04 1511.9 0.01 Psorospermum febrifigum 84.75 0 79.87 0.1 
  H. pulcherima 0 0 1.1 0.01 Psorospermum senegalensis 66.88 0.12 63.23 0.11 
  Hexalobus monopetalus 2.48 0 2.03 0.01 Saba senegalensis 0.17 0.02 0 0.02 
  H. acida 3077.37 0 2907.2 0 Sapium ellipticum 0.14 27.64 0 27.57 
  Hyphaena tebaica 15.19 0.02 13.7 0 Securida longepedunculata 38.49 0 36.1 0 
  Jasmimum dichotomum 0.56 0.01 0.63 0 Senna alata 77.1 0.45 74.77 0.46 
  Keetia cornelia 0.02 0 0.17 0 Senna javanica 0.03 0 0.01 0 
  Keetia multiflora 0.95 2.14 0.07 0.02 Senna sp. 0.07 9.21 0.01 9 
  Keetia venusta 2.5 0.01 1.5 0.01 Senna spectabilis 0.17 0 0.14 0 
  Kigelia africana 0.43 0 0.17 0 Sizygium guiénne  Var macrocarpum 257.07 0 257.07 0 
  Landolphia heudelotii 1.27 0 0.3 0 Sizygium guiennensis var guiennensis 14.24 0 23.5 0 
  Lannea acida 4.1 0 1.53 0 Steganotaenia araliacea 71.22 0.74 68.83 0.75 
  Lannea chimperi 68 0 70.93 0 Sterculia tragacantha 82.32 0 79.31 0.01 
  Lonchocarpus laxiflorus 0.17 0 0.07 0 Strichnos inocula 0.77 2.31 1.04 2.44 
  L. lanceolata 126.98 0 124.83 0 S. spinosa 18.68 0.76 17.7 0.76 
  Mangefera indica 3.98 0 3.87 0 T. indica 0 0.6 0 0.6 
  Maranthes polyandra 0 0 0.14 0 Tectona grandis 0.4 0.12 0.4 0.1 
  Margaritaria discoidea 0.03 0 0 0 Tectonia grandulosa 1.68 0 0.23 0 
  Maysa lanceolata 52.59 0.23 50.97 0.25 Terminalia brownii 0 0 0.21 0 
  Maytenus senegalensis 51.98 0.01 49.97 0 Terminalia dewevrei 0.17 0.05 0.77 0.06 
  Maytenus undatus 0.03 0 2.14 0 T.a glauscescens 614.19 0.35 605.87 0.34 
  Morelia senegalensis 0 0.15 0.02 0.09 Terminalia laxiflora 163.58 0.69 160.97 0.71 
  Musa balbisiana 0 0 0 0 Terminalia macroptera 112.1 0.05 133.4 0 
  Mytragina sp 1 0.04 1 0.01 Terminalia micrantha 143.7 0 120.1 0 
  Neoboutonia velutina 4.85 0.61 4.4 0.67 Terminalia sp 3.28 0 0 0 
  Neocaria macrophylla 31.73 0 24.21 0 Trema orientalis 2.47 0.13 1.46 0.22 



15 

 

 
           

Table 6. Cont’d.            
            

N. congesta 0 0.15 0.14 0.06 Trickilia rocka 40.08 0.64 37.83 0.65   

Ochna Afzeli 6.17 1.14 7.17 1.18 Uapaca acuminata 0.38 0.01 0.07 0.01   

Uapaca heudeloti 0.99 0 2.37 0.02 Uapaca chevalieri 0.06 0.03 1.36 0   

Uapaca paludosa 2.37 0 2.1 0 Vitex madiensis 16.77 1.47 6.25 1.53   

Uapaca sp 0.05 0 5.77 0 Vitex simplicifolia 1.74 1.01 1.6 1.27   

Uapaca vanhouttei 0.07 0.01 0 0.01 Vitex sp1 0.26 0 0 0   

Uvaria angolensis 2.11 0.15 2.12 0.1 Voacanga africana 10.13 1.29 6.63 1.14   

Uvaria chamea 0 2.18 0.25 2.27 Voacanga thoursis 21.5 0.03 20.11 0.03   

Vepris herophylla 6.63 0 0 0 X.  americana 17.25 0.02 10.77 0.01   

Vernonia amygdalina 0.13 0 0.13 0 Xylopia parviflora 0.52 0 0.5 0   

Vernonia sp 0.02 0.02 1.01 0 Zantozilum giletii 3.5 0.02 3.2 0.02   

     Total 11134.2 100 10544 100   

 
Table 7. Comparison of the regeneration rates according to the treatments and the types of savannas.  

 
 T0 T1 T2 T3 Mean Standard deviation 

Shrubby savanna 599.967 292.4 231.833 700.2 456.1 229.038 

Raised savanna 307.567 368.9 306.867 288.567 317.98 35.071 

Wooded savanna 268.267 171 605.6 147.767 298.16 211.503 

Average 391.933 277.433 381.433 378.844 357.41 53.618 

Standard deviation 181.231 99.795 197.7259 287.0683 191.46 76.784 
 

 
fragments of the stems or by the climatic and 
zooanthropic factors. The density per hectares of the 

marked rejections passed from 1319 stems.ha
-1

year
-1

 

in 2004 to 623 stems.ha
-1

 in 2006 in shrubby 

savannas, 1317 stems.ha
-1

 in 2004 to 911 stems ha
-

1
year

-1
 in 2006 in raised savannas. In wooded 

savannas, the density of the rejections passed from  
385 stems.ha

-1
 in 2004 to 158 stems.ha

-1
year

-1
 in 

2006 (Figure 11). 
 
 
Annual mortality of the species 
 
H. acida presents a very high number of dead 

 
 

individuals (66 stems ha
-1

year
-1

) in the three types 

of savannas, followed by P. thonningii (30 stems ha
-

1
year

-1
) and A. senegalensis (23 stems ha

-1
year

-1
) 

(Table 8). In general, shrubby savannas are more 
threatened with regards to the mortality of the stems 

(12 stems ha
-1

year
-1

 on average) per year. Indeed, 
during the first stages of the development, some 
species have a high rate of mortality at the level of 
the seedlings. According to Puig et al. (1989), this 
rate is often higher when the seedlings are gathered 
particularly near the foot of the tree; in fact, the roots 
of the tree emit toxic substances to the plants. The 
seedlings being heliophilous in the first stages of 
development, this mortality can also be due to the 

 
 
weak luminosity under the tree. The action of 
predator, caterpillars or the phytophagous parasites 
is not negligible on the mortality of the seedlings. 
 

 
Floristic diversity in the savannas disturbed by 
the wood cuts 

 
Abundance and specific richness of the 
vegetation 

 
There are abundant and rich species in the 
savannas of the peri-urban zone of Ngaoundéré 
(Table 9). It comes out that species are abundant in 



16 

 

  
 
 

 

1400 
 

1200 
 

1000 
 

800 
 

600 
 

400 
 

200 
 

0   
2004 2005 2006 

 
Figure 11. Evolution of rejects of 2004 to 2006. 

 

 

Table 8. Annual mortality of the species (stems.ha
-1

year
-1

).  

 
 
 
 
 
 
 
 
 
 

 
Shrubby  
 
Raised   
wooded  

 

 
Scientific names A B C Means 

A. zygia 3 3 1 2.01.0 

A.  africanus 4 6 39 16.014.9 

A. senegalensis 42 18 10 23.012.3 

B. ferruginea 1 0 5 2.02.0 

Combretum collinum 1 3 1 2.00.9 

Cussonia bartherii 1 2 5 2.01.4 

C. macrostachys 2 4 2 2.00.8 

E. africana 2 2 2 2.00.2 

D. oliveri 20 23 1 15.09.1 

Ekenebergia senegalensis 1 3 13 5.04.9 

E. sigmoidea 3 2 7 4.02.1 

H. acida 143 50 4 66.051.6 

L. lanceolata 3 2 3 2.00.6 

Protea madiensis 5 36 1 14.014.8 

P. thonningii 56 20 14 30.017.1 

P. febrifigum 9 2 1 4.03.4 

F. glumosa 2 4 1 2.01.0 

Securidaca longepedonculata 7 5 3 5.01.4 

Sizygium guiennense var. macrocarpum 28 8 1 12.010.3 

T. laxiflora 13 3 2 6.04.8 

T.  glaucescens 1 1 1 1.00.2 

T. macroptera 2 4 1 2.01.0 

Steganotegea araliacia 1 0 1 1.00.3 

Trikilia  emmental 3 4 3 3.00.6 

H. madagascariensis 0 0 2 1.00.7 

Voacanga sp. 0 1 2 1.00.8 

Sysygium guiennense var guienense 0 1 2 1.00.7 

Flacourtia indica 1 0 1 0.30.2 

Vitex doniana 1 2 2 1.00.4 

V. madiensis 0 1 0 0.20.2 

Mean 1215 78 44 8.02.7 
 
a: Shrubby savanna; B: raised savanna; C: wooded savanna. 



17 

 

  
 
 

 
Table 9. Specific abundance and richness of species a: specific abundance A; specific richness R.  

 
  T0   T1  T2  T3  Total 
 Types of savannas A R A R A R A R A R 
 Shrubby 240 77 197 67 211 65 205 64 853 273 
 Raised 220 66 208 59 221 67 230 67 879 259 
 Woode 242 81 239 83 247 90 246 76 974 330 
 Tot 702 224 644 209 679 222 681 207 2706 862 

 

 
Table 10. Values of the indices of Shannon (ISH), the equitability of Piélou (EQ), Simpon (D) and its 
reverse (D') of the species in savannas according to the treatments.  

 
 Treatments ISH EQ ISH/EQ D D’ 

Shrubby savannas T0 2.51 0.36 6.97 3.87 0.26 

 T1 2.29 0.33 6.94 2.78 0.36 

 T2 2.15 0.31 6.94 3.14 0.32 

 T3 2.09 0.3 6.97 2.94 0.34 

Raised savannas T0 2.11 0.3 7.03 3.38 0.3 

 T1 1.92 0.28 6.86 3.08 0.32 

 T2 2.2 0.32 6.88 3.38 0.3 

 T3 2.33 0.34 6.85 3.81 0.26 

Wooded savannas T0 2.71 0.39 6.95 4.16 0.24 

 T1 3.02 0.44 6.86 3.9 0.26 

 T2 3.27 0.47 6.96 4.2 0.24 

 T3 2.56 0.37 6.92 4.23 0.24 
 
 

 

wooded savannas with a total of 914. Indeed, the 
distribution of the diaspores in the wooded savannas 
by the zoochores is favourable to the abundance of the 
species. In these savannas, due to the seasonal cultures 
in the forest galleries by some farmers, there is less 
disturbance compared to shrubby savannas. The 
difference between shrubby and raised savannas is the 
weakness of species. They are respectively 853 and 879 
for shrubby and raised savannas. Ficher test at the 
doorstep of 5% shows that there is no significant 
difference between these types of savannas.Specific 
richness in shrubby savannas (273) is largely higher than 
those of raised savannas (259) and wooded one 
(330).The intense activities of wood cuts and grazing are 
generally the factors of the recruitment of new exotic 
species, and are at the origin of this great richness in the 
shrubby savannas. The protected sites (702) are much 
richer. But with regard to the specific richness, there is no 
considerable difference between the various types of 
wood cuts. However, the richness is weak for T3 (207) 
compared to T0 (224). 
 

 

Indices of Shannon, the equitability of Piélou, Simpon 
and its reverse 
 

The indices of Shannon (ISH), the equitability of Piélou 

 
 

 
(EQ), Simpon (D) and its reverse (D'), and the ratio 
ISH/EQ (Table 10) are very high in the three types of 
savannas for the whole types of treatments. 
 

 

Heterogeneity of the vegetation 

 

Histogram of frequency for the whole savannas (Figure  
12) shows that cut savannas present a higher index of 
frequency in species. The species are thus much 
dispersed due to the phenomenon of wood cuts, however 
the vegetation is heterogeneous. 
 

 

Relative frequencies of the species as a function of 
villages and various type of wood cuts 

 

The frequency of the species was evaluated for the 
villages as a function of the treatments in the various 
vegetable formations. It was found that the savannas of 
Dang (University area) present a relative frequency of 
11.21% for treatment T3 in shrubby and raised savannas. 
The impact of students’ activities can explain this high 
percentage. The relative frequencies are about 11.15% 
for the treatments T1 and T2 in the wooded savannas of 
Béka Hooseré where the populations exploit the forest 
galleries for agriculture. The same observations were 



18 

 

 
 
 

 

N
u
m

b
e
rs

 o
f 
s
p

e
c
ie

s
 

 
 
 
 

 
90   
80   
70   
60   
50   
40   
30   
20   
10   

0  
I II III IV V  

Indices of frequency 
 

Figure 12. Histogram of frequency of the species of savannas. 
 
 

 
Table 11. Relative frequencies of savannas according to the villages and the treatments (in %)  

 
 Savannas Dang Béka Borongo Ngaouhoura Mbang Ville Beskewal Daran Tizon Wakwa 

 SA T0 8.07 8.27 10.39 6.52 7.78 6.43 8.53 8.9 11.11 9.67 

 SA T1 8.07 5.4 7.89 4.78 7.39 14.06 6.48 7.72 6.54 6.04 

 SA.T2 7.62 8.27 4.3 8.7 6.23 10.04 10.58 7.42 7.19 8.16 

 SAT3 11.21 9.71 6.81 8.26 5.06 6.02 6.48 8.31 8.5 6.04 

 SB T0 10.76 5.76 8.6 8.26 8.95 6.83 7.51 6.83 7.52 10.57 

 SB T1 8.07 6.83 7.53 9.13 7.39 5.62 8.53 6.23 8.17 9.97 

 SB.T2 8.07 7.91 8.24 10.43 7.78 6.83 5.46 10.39 7.84 8.16 

 SB.T3 11.21 6.83 8.96 9.57 9.73 9.24 7.51 10.09 7.19 6.95 

 SC.T0 8.07 8.27 10.04 7.83 8.17 7.23 8.53 9.2 11.44 10.27 

 SC. T1 7.18 11.15 8.24 10 9.73 12.45 10.24 7.42 7.52 7.55 

 SC.T2 8.52 11.15 7.17 8.7 9.73 8.03 9.21 8.9 7.19 8.76 

 SC. T3 3.14 10.43 11.83 7.83 12.06 7.23 10.92 8.61 9.8 7.86 

 Total 100 100 100 100 100 100 100 100 100 100 
 

SA: shrubby savannas; SB: raised savannas: SC: wooded savannas. 
 
 

 

made in Borongo and Mbang-Mboum for T3 in the 
savannas’ forest galleries with respective frequencies of 
11.83 and 12.06%. Shrubby T1 and wooded T1 of these 
cities respectively present the most significant relative 
frequencies of the whole site of study with the 
percentages of 14.6 and 12.45% (Table 11). The density 
of the population imposed a strong pressure on these 
savannas. 
 

 

Frequencies of the species by families 

 

In the whole savannas, 34 families were identified. The 
most frequent families are Combrétaceae (10.53%), 
Euphorbiaceae (9.77%) and Mimosaceae (7.62%) with 
highest relative frequencies. But for the whole of the flora, 
the leguminous plants (Cesalpiniaceae, Mimosaceae and 
Fabaceae) are most significant in relative frequency 

 
 
 

 
(Table 12). On the other hand, the Sapindaceous are 
more raised in percentage (15 %) followed by 
Euphorbiaceae with 7.86%. 
 

 

Analysis of autoecologic characters 

 

Biological types 

 

Table 13 presents the biological types of the savannas. It 
arises that the Microphanerophytes (McPh) are dominant 
with 62.80%, while Mesophanerophytes (MsPh) 
represent 19.49%. The least represented are Megapha-
neorophytes (Mg pH) with 2.75%. This little percentage is 
explained by the low density of the trees with heights 
greater or equal to 30 m. The great representativeness of 
the microphone and mesophanerogames explain that 
these biological types adapt easily to guinean sava



19 

 

 

 

 
Table 12. Frequency of the families of the vegetation of Ngaoundéré.  

 
 N° Families FA FR NE % 

 1 Anacardiaceae 87.50 3.83 3 2.14 

 2 Annonaceae 120.0 5.25 5 3.57 

 3 Apiaceae 43.33 1.90 1 0.71 

 4 Apindaceae 53.33 2.33 2 1.43 

 5 Apocynaceae 45.00 1.97 6 4.29 

 6 Araliaceae 76.67 3.35 1 0.71 

 7 Arecaceae 9.17 0.40 1 0.71 

 8 Asteraceae 5.00 0.22 1 0.71 

 9 Burseraceae 4.17 0.18 1 0.71 

 10 Célastracaea 38.33 1.68 1 0.71 

 11 Cesalpiniaceae 165.00 7.22 7 5.00 

 12 Combretaceae 240.83 10.53 7 5.00 

 13 Euphorbiaceae 223.33 9.77 11 7.86 

 14 Fabacaea 80.00 3.50 5 3.57 

 15 Flacourtiaceae 28.33 1.24 4 2.86 

 16 Hymenocardiaceae 84.17 3.68 1 0.71 

 17 Hypericaceae 155.0 6.78 3 2.14 

 18 Indéterminée 21.67 0.95 2 1.43 

 19 Meliaceae 56.67 2.85 8 5.71 

 20 Mimosaceae 174.17 7.62 1 0.71 

 21 Moracaea 78.33 3.43 10 7.14 

 22 Myrsinaceae 20.00 0.87 10 7.14 

 23 Myrtacaea 90.00 3.94 1 0.71 

 24 Myrtaceae 15.00 0.66 2 1.43 

 25 Ochnaceae 83.33 3.64 1 0.71 

 26 Olacacaea 20.00 0.87 5 3.57 

 27 Polygalaceae 23.33 1.02 1 0.71 

 28 Proteacea 35.00 1.53 1 0.71 

 29 Rubiaceae 77.50 3.39 1 0.71 

 30 Rutaceae 8.33 0.36 6 4.29 

 31 Sapindaceae 6.67 0.29 21 15.00 

 32 Tiliaceae 17.50 0.77 1 0.71 

 33 Ulmacaea 15.83 0.69 5 3.57 

 34 Verbenaceae 84.17 3.68 4 2.86 

  Total 2286.67 100.0 140 100.00 
 

F: Absolute frequency; FR: Relative frequency; N E: Species/family numbers; 
Percentages of species/family. 

 

 

of Adamaoua. There is no significant difference (P<0.05) 
among the treatments and between the savanicole types 
of formation. 
 

 

Physiognomical distribution 

 

Trees dominate the savanicole formation of the peri-
urban zone of Ngaoundéré. They represent 66.07% of 
the woody flora while 33.93% is represented by the 
shrubs (Table 14). This result shows that the vegetation 
of Ngaoundéré is a high guinean savannas formation 

 
 

 

where the species are among species of the wet dense 
forest and those of the sahelian savannas. 
 

 

Phytogeographical distribution of the species 

 

The pantropicale species represent 96.80% of the whole 
flora (Table 15) while the Afro american species (AA) are 
represented by 0.90% of the flora, indeed these species 
are not in their surface of phytogeographical distribution. 
The flora is always made up at the same time of groups 
with more or less vast distribution, and endemic groups. 



20 

 

 
 
 

 
Table 13. Distribution of the biological types.  

 
 Types of savannas Treatments Mc Ph Mg Ph Ms Ph Nn Ph Total 

 Shrubby savanna T0 5.46 0.25 1.70 1.30 8.71 

 Shrubby savanna T1 4.66 0.14 1.23 1.27 7.30 

 Shrubby savanna T2 4.77 0.18 1.55 1.37 7.88 

 Shrubby savanna T3 4.77 0.14 1.12 1.48 7.52 

 Raised Savanna T0 5.13 0.29 1.45 1.27 8.13 

 Raised savanna T1 4.70 0.25 1.41 1.41 7.77 

 Raised savanna T2 5.06 0.25 1.63 1.23 8.17 

 Raised savanna T3 5.46 0.33 1.52 1.27 8.57 

 Wooded savanna T0 5.57 0.25 1.81 1.30 8.93 

 Wooded savanna T1 5.68 0.18 1.99 0.94 8.79 

 Wooded savanna T2 5.75 0.18 2.21 0.98 9.11 

 Wooded savanna T3 5.78 0.29 1.88 1.16 9.11 

 Total  62.80 2.75 19.49 14.97 100.00 
 
 

 
Table 14. Physiognomical distribution of the flora of Ngaoundéré.  

 
 Type of savannas Type of the wood cuts Trees Shrubs Total 

 Shrubby savanna T0 5.94 2.77 8.71 

 Shrubby savanna T1 4.35 3.02 7.38 

 Shrubby savanna T2 4.97 2.88 7.84 

 Shrubby savanna T3 4.93 2.66 7.59 

 Raised savanna T0 5.36 2.77 8.13 

 Raised savanna T1 4.97 2.81 7.77 

 Raised savanna T2 5.33 2.81 8.13 

 Raised savanna T3 5.47 3.17 8.64 

 Wooded savanna T0 6.12 2.77 8.89 

 Wooded savanna T1 6.08 2.66 8.74 

 Wooded savanna T2 6.33 2.73 9.07 

 Wooded savanna T3 6.23 2.88 9.10 

 Total  66.07 33.93 100.00 
      

 
 

 

A strong proportion of species to broad distribution can 
be an indication of degradation. The soudano-zambezian 
species are null. The whole savanicole formations are 
dominated by annual grasses. 
 

 

Impact of wood cut on the dissemination of the 
diasporas 

 

Table 16 presents the types of the diaspores met in the 
peri-urban zone of Ngaoundéré. It releases from this 
table that the zoochores (18.56%) present a significant 
rate of dissimilation for the T0 treatment in the shrubby 
savannas. In protected savannas, the animals are the 
first freight agents of the diaspores. The second agents of 
dissemination in the shrubby savannas are anemochores 
(11.92%). The barrochores and hydrochores are found in 
small percentage in the wooded savannas. In the forest 

 
 

 

galleries, the barrochores are significant. According to the 
size of these diaspores, the speed of dissemination is 
low. It can be quoted that Strichnos spinosa are species 
with low speed dissemination. The agents of their 
dissemination are the wind, the streaming water and the 
domestic animals. 
 

 

DISCUSSION 

 
Impact of the wood cuts on the structure of the 
vegetation 

 

The size and the diameters of the stems in the savannas 
of the peri-urban zone of Ngaoundéré have a structure of 
the type ”L''. This structure is the result of a strong 
pressure of the wood cuts on the vegetation. Indeed, the 
repeated wood cuts by the population of Ngaoundéré do 



21 

 

  
 
 

 
Table 15.  Phytogeographical distribution of the species.  

 
  Type of savannas Treatments  AA Pan PRA  Tot    

      T0  0.07 8.38 0.25  8.71    

  Shrubby savanna  T1  0.04 7.16 0.18  7.38    

      T2  - 7.66 0.18  7.84    

      T3  0.04 7.34 0.22  7.59    

      T0  0.04 7.95 0.14  8.13    
  Raised savanna  T1  0.07 7.63 0.07  7.77    

      T2  0.04 7.95 0.14  8.13    

      T3  0.11 8.38 0.14  8.64    

      T0  0.07 8.56 0.25  8.89    
  Wooded savanna  T1  0.18 8.31 0.25  8.74    

      T2  0.18 8.60 0.29  9.07    

      T3  0.07 8.85 0.18  9.10    

  Total      0.90 96.80 2.30  100.00    

 Table 16. Dissemination of the species in savanna.            
           

 Types of savanna  Shrubby savanna   Raised savanna   Wooded savanna  

 Treatments T0 T1 T2 T3 Tot T0 T1 T2 T3 Tot T0 T1 T2 T3 Tot 

 An 2.9 2.99 2.87 3.13 12 2.78 3.5 3.36 3.36 13 2.66 2.25 3.63 2.78 11.32 

 Ba - - - - - 0.02 - - - 0.02 0.19 0.02 - - 0.21 

 Hy - - - - - - - - - - - - 0.02 0.05 0.07 

 Sa 0.8 0.65 0.49 0.46 2.4 0.9 0.7 0.72 0.97 3.26 1.37 1.53 0.95 1.34 5.19 

 Sc 0.2 0.05 0.14 0.09 0.5 0.09 0.1 0.07 0.14 0.39 0.23 0.19 0.16 0.23 0.81 

 Zo 4.4 4.65 4.84 4.65 19 4.54 4 4.19 3.87 16.6 3.89 4.35 3.56 3.94 15.74 

 Tot 8.3 8.33 8.33 8.33 33 8.33 8.3 8.33 8.33 33.3 8.33 8.33 8.33 8.33 33.33 
 

An : Anémochores, Ba : Barochores, Hy : Barochores; Sa: Sarcochores, Sc : Sclérochores, Zo : Zoochores 
 

 

not make possible quick reconstitution of the vegetation. 
This situation was checked in shrubby savannas with 
very strong and repeated cuts on the same trees during 
three years. It can be noted that seedlings with heights 
less than two meters and trees with little diameters are 
threatened in the whole savannas because of the 
intensity of wood cuts compared to the adult subjects; this 
justifies the structure in L of the vegetation of 
Ngaoundéré. These results corroborate those of 
Chouaibou (2006). In general, such a structure presents 
a good regeneration of the arborescent layers of the 
vegetable communities (Anonymous, 1987). This result 
approaches those of Mbolo (2005) who worked in the 
reserve of the biosphere of Dja, Southern Cameroon, but 
differ from those of Amougou (1986), Sonké (1998), and 
Gudjé (2002).  
Indeed, the wood cuts are not the only factors that give 
this structure to savannas of Ngaoundéré, there are also 
some factors not controlled like bush fires and the grazing 
practices which should be integrated to really understand 
the structural dynamics of the savannas. If Ntoupka 
(1999) integrated these parameters in his work 

 
 

 

in the area of the far-north region, it was to seek 
exactlywhich was the major factor of modification of the 
structure of the vegetation of Sudanese savannas 
 

 

Impact of the wood cuts on the floristic composition 
of the species 

 

In our study we had on average 140 species, 60 kinds 

and 34 families; 371 alive stems.ha
-1

year
-1

in 2004 and 

351 stems.ha
-1

 in 2006. These results are similar to those 
of Thorgnang (2001) who listed 117 species in 80 kinds 
and 37 botanical families in the forest of Gawar. Our 
results are greater than those of Mahamat (1991) in the 
national park of Kalamaloué (4500 ha), with 21 species in 
11 botanical families and that of Teitcheugang (2000) 
with 75 species in 46 kinds and 24 Families in the forest 
reserve of Zamay.  

The richness of the savannas of Ngaoundéré would be 
due to the anthropic factors which would support the 
dissemination of the species from an area to another. 
Noubissié (2005) and Tchobsala (2003) showed that D.



22 

 

 
 
 

 

oliveri is classified among the species that are more 
suckering in Adamaoua. As a whole, the number of the 

alive stems (371 stems ha
-1

year
-1

 in 2004 and 351 stems 

ha
-1

year
-1

 in 2006) is more significant compared to the 
results of several authors who worked on floristic 
diversity. 
 

 

Dynamics of the reconstitution of the vegetation 
under the effects of the wood cuts 

 
Reiterative capacity of the trees in savannas without 
cuts and with wood cuts 

 
The results showed that the average density of the 

rejections is 3712.45 stems.ha
-1

year
-1

 for the individuals 
with circumference less than 3 cm in natural savannas. It 

is 1423.41 stems.ha
-1

year
-1

 for individuals with 
circumference greater than 3 cm. The number of natural 
rejection is more significant compared to that of 
Teitcheugang (2000) in the forest reserve of Zamay 

(1133 ind.ha
-1

year
-1

) for the individuals with diameter 

lower than 3 cm, 489 stems ha
-1

year
-1

 for the individuals 
with diameter greater than 3 cm. The density of 
regeneration is higher than that found in the savannas of 
Houbaré where Combutum glutinosum is the densiest 

species in terms of regeneration with 700.36 stems.ha
-1

. 
This species is least used by the local population. In 

addition to this species E. Africana (272.27 stems ha
-

1
year

-1
), Combutum sp. (198.27 stems ha

-1
year

-1
), H. 

acida (164.45 stems.ha
-1

year
-1

) have densities of more 
significant regeneration. Teitcheugang (2000) found 

573.8 stems.ha
-1

year
-1.

in the forest reserve of Zamay. 
Our results are less than those of Guejé (2002) (5613 

stems.ha
-1

year
-1

) for the trees which heights of the 
seedlings are lower than 100 cm. Indeed the work of the 
later one was not carried out under the same conditions. 
It was carried out in the reserve of Dja in the Southern 
Cameroon where the climate is favourable to 
regeneration.  

The capacity of reiteration of the seedlings is very 
significant at the time where trees are cut. In the 
savannas of Ngaoundéré, H. acida and D. oliveri are the 
two species which have a fast capacity of regeneration. 
The wood cuts would support the regeneration of the 
seedlings. These results corroborate those of Tchobsala 
(1997, 2003) where D. oliveri for example regenerated 
quickly and in abundance after wood cut and especially 
after bush fire.  

The second strategy of regeneration would be the ger-
mination of seeds. If in this work the most cut trees (T3) 
result in very rich seedlings from germination, the freight 
agents played a very significant role in the dissemination 
of the diaspores. Cut woods are quickly replaced and 
recolonized by new species. Endada africana and 
iliostigma thonningii are species which have a fast 
regeneration rate in savannas of the peri-urban zone of 

 
 
 
 

 

Ngaoundéré (Tchobsala, 1997).  
In terms of regeneration, the density of the rejections is 

more significant in the cut pieces. It is this dynamics of 
regeneration that makes it possible in the savannas of the 
peri-urban zone of Ngaoundéré. If the local popu-lations 
do not make successive cuts on the same pieces and 
leave savannas in fallow for two to three years, the 
vegetation of Ngaoundéré would not suffer from the 
phenomenon of degradation. 
 

 

Mortality of the rejections without wood cuts 

 

The death rate of the seedlings is very remarkable in 
wooded savannas. This is mainly due to the effects of 
moisture in the rainy season, the termites and the 
trampling of the animals for the watering in dry season. 
Sist et al. (1989) showed that the presence or the 
absence of the seedlings and their densities does not 
depend solely on the viability of seed but also of the 
ecological conditions (light intensity, hydromorphy of the 
ground).  

The mortality of the seedlings is also very marked in 
shrubby savannas due to the fact that these areas are 

grazing  areas  for  domestic  animals  and  subjected  to 
successive cuts. The trampling of the animals makes lose 

a great number of the seedlings. In the same way, the 
repeated cuts affect the potentialities of development of 

the seedlings. 
 

 

Mortality of the rejections after wood cuts 

 

The competition between the seedlings resulting from the 
rejections after wood cut is very marked in the first year 
when these seedlings are gathered near the tree’s foot as 
in the case of H. acida and S. guinense var 
macrocarpum. The roots of the tree secrete toxic 
substances to the plants and the seedlings being 
heliophilous in the first stages of the development. The 
mortality can also follow the weak luminosity below the 
tree’s foot. The action of predator, the caterpillars or the 
phytophagous parasites is not negligible on the mortality 
of the seedlings. This confirms the works of Puig et al. 
(1989) who showed that the death rate of the rejections is 
often higher when the seedlings are gathered in particular 
near the tree’s foot. Tchakounté (2001) showed that bush 
fire is not a negligible factor on the mortality of the 
seedlings. The death rate also depends on the age and 
the stage of development of the seedlings. Gudjé (2002) 
showed that in the reserve of biosphere of Dja, the risk of 
mortality of the seedlings decreases quickly when one 
passes from the young plants resulting from germination 
to the young trees installed in under wood. 
 

Indeed while comparing the results of the two types of 
regenerations (without cuts and with wood cuts), one 
realizes that the mortality of the seedlings is more 



23 

 

 
 
 

 

significant in the cut pieces than in the pieces without 
cuts. 
 

 

Dynamics of reconstitution of savannas of 
Ngaoundéré 

 

Letouzey (1968) admitted that savannas perished without 
the presence of man. From our results under the 
influence of the repeated and anarchistic wood cuts in the 
peri-urban sector of Ngaoundéré, it would be difficult that 
savannas find their state of forest if the local populations 
are not put in co-administration with the ministries of 
forests and the structures specialized in the environ-
mental protection; this fear is justified by the population’s 
increase. An alternative solution would be to leave 
savannas in fallow in some few years so that they should 
quickly reconstitute.  

The statements of the floristic composition of some 
sites in the forest galleries and savannas from 2004 to  
2006 confirmed the declarations of Letouzey (1968): 
"some shrubby savannas with T. glaucescens, P. 
thonningii, Bridelia ferruginea, can settle gasoline 
sowings forest".  

Factors like wood cuts, precipitations and fires play an 
important role into the forest dynamics of savannas 
(Séghièri, 1990). These factors are responsible for the 
phenomena of embushment which corresponds to the 
degradation of a savannas towards denser vegetable 
formations dominated by one or some woody species. 
The dominant species of embushment in the area are: T. 
glaucescens, H. acida, P. thonningii and A. senegalensis. 
These species are generally essential for rejections and 
germination. 
 

 

CONCLUSION AND RECOMMENDATIONS 

 

The wood cuts negatively influence the structure and the 
floristic diversity of the vegetation in the peri-urban zone 
of Ngaoundéré. The types of the wood cuts have 
structures in "L". Such a structure generally presents a 
good arborescent regeneration after cuts. The density of 
the stems is more significant in shrubby savannas with 
heights between 0 and 200 cm. In the three types of 
vegetable formations, there is a reduction in the number 
of the stems when the heights of the trees increase. From 
200 cm the number of the stems is almost null.  

The number of the stems decreased from 2004 to 
2006. This justifies the regression of the wet savannas of 
Ngaoundéré. The characteristic and indicating species in 
the shrubby savannas under the strong pressure of the 
wood cuts are represented by H. acida, P. thonningii and 
A. senegalensis. On the other hand, for those of the 
wooded savannas are D. oliveri and Cesalpinia sp., the 
very high cuts are depressive for the stability of the 
savannas and the disappearance of the vegetable 

 
 

  
 
 

 

biodiversity. Consequently, they are responsible of the 
accelerated degradation and the alarming installation of 
the desert in wet savannas of Ngaoundéré. The intolerant 
species towards wood cuts are T. indica, S. 
longepedunculata, Parkia biglobosa S. spinos etc., These 
species can disappear easily when the pressure of the 
wood cuts is significant. Savannas of the peri-urban zone 
of Ngaoundéré have 142 species, 60 kinds and 34 
families. The most represented families are 
Combrétaceae (10.53%), Euphorbiaceae (9.77%) and 
Mimosaceae (7.62%), they present the strongest relative 
frequencies.There are two dynamic methods for the 
regeneration of the species: Regeneration by germination 
of the diaspores and regeneration by rejection or 
drageonment after cut. The species that suffer after cuts 

are: H. acida (170 stems ha
-1

year
-1

), P. thonningii (76 

stems ha
-1

year
-1

), Annona senegalensis (35 stems.ha
-1

) 

and H. madagascariensis (30 stems ha
-1

year
-1

), D. 
oliveri, A. africanus and P. aquatica.  

The biological types are dominated by trees formation. 
They represent 66.07% of the woody flora. 33.93% is 
represented by the shrubs. From the phytogeographical 
point of view, the panatropicales species represent 
96.80% and the zoochochores 18.56%, showing a 
significant rate of dissimilation for the treatment T0 in the 
shrubby savannas.  

The reconstitution of the savannas of Ngaoundéré is 
possible if the population reduces the rate of the wood 
cuts. To preserve the structure of the vegetation, some 
measure in co-administration between the government 
and the population should be considered to safeguard the 
anthropized vegetation of Adamaoua. A dialogue among 
the civil authorities, administration in charge of forest, the 
local population, the nongovernmental organizations and 
the researchers is on the way to be installed in the region 
of Adamaoua.  

To protect this threatened biodiversity, the populations 
could also choose inspection committees and forests 
guards, annual practise rotative and selective wood cuts. 
They should severely sanction those who cut wood 
fraudulently. It is recommended to the population to be 
aware on the wood cuts which are a danger to the 
survival of the vegetation consequently to the installation 
of the desert within the wet savannas of Adamaoua. Co-
administration will encourage the collective plantations 
and community forests and expresses a wish of creation 
of the structures of the participative follow-ups (GIC, 
associations, etc) for the protection and the safeguard of 
stressed savannas. 
 

 

ACKNOWLEDGEMENTS 

 

We are thankful to the project PRASAC/ARDESAC for 
collaboration in this paper. We are also grateful to Doctorr 
ONANA Joseph and Professor TCHOTSOUA Michel for 
assistance. 



24 

 

 
 
 

 
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