Description of Study Sites

Investigations were carried out in three sites belonging to the Mayo-Kani division in the Extreme-North region of Cameroon. These sites are notably: Kilguim, Going I, and Going I (Figure 1). The Soudano- Sahelian zone is characterized by fragile ecosystems, a high population density and intense pressure on land. It is subjected to the adverse effects of dryness exacerbated notably by deforestation and soil erosion. The different sites chosen belong to the great massive of the Extreme-North region and more precisely in the Mayo-Kani are submitted to the Soudano-sahelian climate which dominates the zone of Kaele. It is characterized by two unequally distributed reasons: one is the length of the dry season of about eight (08) months, from October to May and a short rainy season of four (04) months, spanning from the month of June to September. The dry season is characterized by a pendulous or oscillating temperature between cold (November to January) and canicular heat (February to May). The mean temperature is 28.1^oC with a minimum of 18^oC in January and a maximum of 40^oC in April and May. The amplitudes of average precipitations are 809 mm per year.

Figure 1

Study site localization

Socio-economic inquiry

Socio-economic, environmental and forestry inquiries were realized close to the populations of three (03) villages (Kilguim, Going I and Going II), delegations of the environment and NGOs. In each village, 50 persons where interviewed, 05 forest guards in each site and thus a total of 15 forest guards in the three sites, five (05) persons in each delegation (regional and departmental delegation) of Maroua, Kaele and equally (05) persons in each of the following organizations (GIZ and ABIOGeT) of Maroua. Inquiries or investigations also continued at the level of the council of Kaele through an interview granted by 10 council agents. A total of 200 persons were interviewed. The great rubrics exploited in the questionnaire are the knowledge of the population about the reforestation programs and its implementation, its implication in her management and its approbation, the difficulties faced by the parties engaged in the management of operation green-Sahel sites. The inquiry was semi-structured with questions of open, closed and oriented nature.

The methodology presents the demarche used to obtain teachings taken from the reforestation of Mayo- Kani as well as of Cameroon. For this reason, we based our research on the classical method of data collection which is an extended bibliography, investigations and interviews granted by parties engaged in reforestation and data collectors of the reforested sites. This present work is currently going on the field, in the North delegations of the environment, the Extreme-North, Mayo-Kani, ABIOGeT (Maroua) and in the sites at the level of forest guards. The inquiries carried out pivoted on ethno-botanic investigations (reforestation problem) and that carried out on the field consist of caring out botanic inventories of reforested tree species. These investigations took place in three sites, all belonging to a division of the Extreme-North region. These sites are notably: Kilguim, Going I and Going II. These three sites were established in 2013.

Floristic data collection and dendrometric measures

The sampling technic was used for the inventory of different reforested species is the quadrant method. This method permits us to collect floristic data and was applied by (Poissonnet & César, 1972) , for the survival of savanna vegetation on the permanent lines andTchobsala (2011) on the peri-urban savanna vegetation of the Adamaoua (Cameroon). This technic was consisting of delimiting parcels or plots of 50mx50m for the inventory of the vegetation following layouts of 10m wide and 50m long one after the other. The experimental dispositive shows three (03) reforestation sites (Kilguim, Going I and Going II sites) and the numbers 1, 2, and 3 represents the number of repetitions. These floristic data collected has permitted the bringing out of: the circumferences at 1.30 from the soil; circumferences at 0.3 from the soil; the diameter of the trunk; the height of the plant; the number of death and living plants with the objective of evaluating the mortality rate; anthropic indices (cutting of wood, bush fire, grazing…).

In total nine (09) quadrants of 50mx50m were realized for all the three sites, with a total of 03 quadrants per site. A rob of 50m long was used to delimit these quadrants. In each site, a surface area of 3/4ha was exploited, thus a total of 2.25 ha for all the 09 parcels of a dimension of 50x50m each. In this surface area of 2025ha, reforested species will be marked. The diameter at the height of the chest level (dbh) and the diameter of the trunk of each plant will be evaluated with the help of a meter ribbon of 30m long. The height of the tree will be evaluated by a pole or stick of 4m long and for plants with heights greater than 4m tall, will be estimated. A brief description of the ecological milieu of reforested species will equally be in the quadrants, and thanks to a digital camera, snap shots or images will be taken.

Frequency of ligneous species

The absolute frequency of a species is the number is this number of individuals of that species counted in the site. According to Braun- Blanquet (1932), the relative frequency is the proportion expressed in percentage between the number collected that contain this species and the total number counted divided by 100.   This method permits the determination of accidental, accessory, less frequent, frequent and most frequent species (Table 1).

Problems of Mayo-Kani division reforested sites

Inquiries, has shown that the local population (67.56±25.95), delegations of MINEDEP (55.56±29.55), NGOs (50.56±23.88), and councils (52.59±32.41) noticed eighteen (18) reforestation problems (Table 2). These problems include bush fires (83.50±16.01), lack of plausibiity studies (78.50±13.99) and lack of bore holes (76.00±19.10), the lack of specialised structures in the domain of reforestation (72.83±13.03) and insufficiency of sensitisation of the local population on the importance of reforestation (71.67±27.55). These results shows that the reforestation of the Mayo-Kani zone is faced with numerous problems both from the environmental and social domain. These results are similar to that of R (RIDDAC, 2016), which shows that many factors render the results of the different reforestation programs less visible.

Anthropization index in reforested sites

Table 3 shows( 82.67±6.43) of burns observed in the three (03) different study sites. This practice of bush fire is translated by the discontent of forest guards and most especially on the ignorance of the local population on the importance of reforestation. The cutting of wood (68.00±12.17) within the sites is the dominant activity after the practice of bush fires followed by pruning (64.00±9.17). These activities show that the reforested sites are accessible despite its access prohibition. This variability is confirmed by variance analysis which discovered the existence of a significant difference between the anthropization indices (P<0.001).

Man’s action influences the natural milieu. In the sites of study, cutting of trees, burning, pruning and trimming were remarkably observed. Bush fire is one of the dominant practices in the sites. These results are similar to that ofTchobsala (2011) in the peri-urban zone of the Adamaoua region, on the impact of deforestation.

Regeneration capacity of species of reforested sites

Mortality rate of plant species according to reforested sites

Figure 2 shows the mortality rate of plant species on different sites. This rate is very high (15%) in the Kilguim site. It is more elevated in this site because of the soil quality, lack of maintenance because of lack of bore holes for watering or because of activity of bush fires. In the Going I and Going II sites, the mortality rate is respectively 6036 and 8.79. These rates are equally considerable and indicates negligence in the maintenance, follow up of reforestation activities, these results corroborate with that of the Sahel (2014) which shows that 60% of reforested sites fail now our days in the Extreme- North region because of lack or inappropriate follow up.

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Figure 2

Percentages of mortality rate of species.

Evaluation of percentages of living and dead plant individuals

The success rate of the Going I, Going II, and Kilguim sites is at an average 80%. Figure 3 below translate this perception. This result is close to that of Sahel et al., 2014 in the Mayo- Kani division, which shows that these results are all below 78%. These results are comparable to a few close exceptions. Despite these success rates in the Mayo-Kani division and the collective consciousness, the Mayo- Kani populations recusant to reforestation activities. This thus reflects a problem of mentality which necessitates reeducation. In the reforested site of Going I, Figure 3 shows 38.16% of living plants, 31.67% in Going II and 30% in Kilguim with respect to the total number of individual plants of the three sites. The percentages of living individuals vary in relation to the villages as well as the death percentages 9.61% in Kilguim, followed by 6.22% in Going II and 4.55% in Going I. these results corroborate to that obtained byTchobsala (2011) in the peri-urban zone of the Adamaoua region, which found the number of living individuals more elevated than the number of dead individuals. This variability is explained by the analysis of variables which shows that there exists a significant difference between the percentage of living individuals and percentage of dead individuals with P= 0.0007.

Figure 3

Percentages of living and dead individuals

Floristic composition, indices of floristic diversity

The floristic record presents 864 ligneous individuals distributed in 30 species, 20 genus and 13 families (Table 5). The Going I site is richer in species diversity with 322 species, while the Kilguim and Going II presents 286 and 246 individuals. But only the Going II is rich in family diversity with 13 families. However, the Shannon-Weaver index varies considerably from one site to the other. It varies between 1.92 and 2.71 bits in the different reforested study sites. It is more elevated when a great number of species participate in the occupation of the soil. It is expressed in bits per individual, and varies from the weakest diversity (0 bits) to the most elevated (4.5bits) (Frontier et al., 1995). This result shows that the Going I (2.71 bits) of Shannon diversity calculated to a more elevated diversity of the other two sites Going II and Kilguim.

   The calculations of Piélou’s equitability attached to the Shannon index confirms the fluctuations between the values of diversity index. In effect, the equitability values vary between 0.33 and 0.48 and the ratio of the index of Shannon to that of equitability, is almost constant as well as that Simpson diversity (D) index are almost identical. In a general manner, there is thus more chance that equilibrium exists in the distribution of reforested species.

Ecogical repartition of species in the reforested sites

Figure 4 illustrates the histogram frequency of ligneous species inventoried in different sites. Rare species (06.67%) is the case of the species index (I) with a total of 11 species, (36.67%) of species having a frequency index equal to (II) and are termed accessory species. Species whose frequency index is equal to III, represents 13.33% of the inventoried flora. Species with index of IV represents 30%, 09 species of the inventoried flora are species said to be frequent and very frequent species are those with index equal to V, representing 13.33% with 04 species. The result presents in the form of a deformed M. the frequency index equal to II, accessory species (36.67%) are more represented followed by frequent species of index IV (30%). This structure of the vegetation translates a certain heterogeneity of milieu because of reforestation and the prohibitioTchobsala (2011) of the sites. This result is different from that of$ in the peri-urban savanna of Ngaoundere which is in the form of an L and which shows that the vegetation represents more accidental species of index I (84%).

Figure 4

Effect of species according to frequency indices

i. Floristic family diversity of different study sites

In this study, 864 individuals were encountered, they belong to 13 botanical families. The percentages of families vary in relation to sites, figure 5. Notwithstanding, certain families are present in certain sites but absent in others. Families of species present in the Going I site: in this site, we encountered 220 species for 10 families: Anacardeaceae (10), Balamitaceae (22), Caesalpiniaceae (149), Capparaceae (2), Combretaceae (85), Meliaceae (16), Ramnaceae (5), Minosaceae (20), Rubiaceae (19) and Ascléapidaceae (01).

The Going II site presents for 13 families: Anacardeaceae (03), Balamitaceae (21), Barsenaceae (17), Caesalpineaceae (25), Capparaceae (2), Combrétaceae (52), Euphorbiaceae (2), Meliaceae (28), Mimosoceae (72), Rhamnaceae (8), Rubiaceae (26), Tilliaceae (16) and Asclepiadaceae (1). The Kilguim site presents 260 individuals and 59 species, 12 families: Balaniteaceae (30), Burseraceae (1), Caesalpipeaceae (40), Capparaceae (30), Burseraceae (1), Casalpipeaceae (40), Caparaceae (10), Compretaceae (12), Euphorbiaceae (1), Miliaceae (54), Mimosaceae (99), Rhamnaceae (1), Rubiaceae (4), Tilliaceae (5) and Asclepidaceae (3).

In the Kilguim represents 260 individuals, 59 species and 12 families.

Family floristic diversity shows that the Mimosaceae and Caesalpineaceae are the most abundant thus the dominant families of the study sites, followed by the Combretaceae and Meliaceae which are more or less represented in the different study sites. It contributes to the floristic richness of ligneous plants. This result shows that Mimosaceae, Caesalpineaceae and Combretaceae are the most adapted families in the Mayo-Kani zone. This result corroborates with that ofBoubacar (2010) at the Faculty of Science/ UAM in Niamey Niger that the most represented families in reverdis are the Mimosaceae (17.39%), Cesalpineaceae (13.04%) and Combretaceae (13.04%). For (P= 0.5147), there exist no significant statistical effect on the number of families recorded in the three sites of study at a confidence level of 95.0%.

Figure 5

Families of the vegetation of sites with respect to stem effectif

ii. Specific diversity of vegetation of sites

Analysis of floristic richness has permitted the identification of 30 species in all the sites. Table 6 shows the list of inventoried species; the most frequent species are: Balanites aegyptiaca with 135 individuals and a relative frequency of 4.49% followed by Piliostigma thonningii with 124 inventoried individuals with a relative frequency of 4.49% followed by Anogeissus leiocarpus with 93 individuals.

Inventoried species are repartition in 13 familiesTable 7. Certain families are represented by a great number of species like the Caesalpineaceae family with 214 species, followed by the Mimosaceae and Combretaceae with 191 and 149 species respectively.

iii. Structure of the vegetation in relation classes of height

Figure 6 represents the structure of the vegetation in relation to the different classes of height in all the three sites put together. The vegetation presents a structure in the form of a cloche translating a homogeneity, more or less acceptable of the ligneous strata. The numbers of stems are more elevated in the class of 1 to 1.50m length and averagely elevated between the classes of 0.5 to 1m and 1.50 to 2m in the three sites of study. The increase in the number of stems in the class 1 to 1.50m shows that the vegetation of reforested sites is impotant. These results are justified by the fact that these three sites were all reforested in the same year, 2013.

Figure 6

Structure of vegetation in relation to classes of height

iv. Distribution of plant vegetation in classes of DBH

All the trees of the three reforestation sites in the three villages presents a structure in the form of a cloche «^», translating a good regeneration of plant species used. In the reforested sites, there is a reduction in the number of individuals when the diameter of the trunk of trees increases (Figure 7). In a general manner, reforestation impacts the structure and repartition of species in reforestation sites. The vegetation presents a structure in the form of cloche “^” because of reforestation and the prohibition of reforested sites. These results do not corroborate with that ofMbolo (2005) on the typology and cartography of Dja Biosphere Reserve of Cameroon, which shows that the vegetation presents an “L” structure because of the high pressure mounted on it by the cutting of trees.

Figure 7

Structure of the vegetation in relation to the classes of DBH

Distribution of the vegetation in function of trunk diameter

The vegetation presents a structure in the form of a cloche, with many individuals which develop instantaneously because of reforestation process and the prohibition of these sites (Figure 8). Such a structure generally translates from a good development of arborescent strata of plant communities. Reforestation effectively impacts the structure and distribution of species in the natural savanna. Variance analysis shows that there exists a highly significant difference (0.001< 0.05) between the classes of trunk diameter. These results are similar to those of (Anonymous, 1987) on the valorization of arid territories and the fight against desertification.

Figure 8

Vegetation structure in relation to trunk diameter

Analysis of variables of principal components

Analysis of variables of principal components (ACP) shows that the Going I village and Going II are positively correlated between them and are opposite to that of the Kilguim village with respect to the abscissa axis (Figure 9). Species such as Piliostigma thonningii, Balanites aegyptiaca, Anogeissis leiocarpus, Combretum glutinosum and Azadirachta indica are the most represented in the study zone. Species dispersed in more dense parts are does that we have the chance of at least encountering them in all the study zones. The other species which are less represented forms clouds around the two (f1 and f2 axis: 92.48%). Species represented in the form of clouds are less dense thus we cannot encounter them in all the study sites.

Figure 9

Distribution of inventoried species

Durable exploitation of reforested sites

The protection and restoration of nature, has to be essentially looked after by a rational organization, targeting the deletion of causes of degradation and to reassure the regeneration of the vegetation with both ligneous and herbaceous species alike (Ferlin, 1981). With respect to data of inquiries and those of floristic recordings, it becomes possible for us to make a certain number of remarks and then envisage an organization plan. To better preserve and conserve biodiversity of reforested sites, Table 8 shows seventeen (17) propositions on the organizational plan, were chosen by the population and the organizations that take part in reforestation programs. The sensitization of the local populations on the role of trees (68.57), presents a very elevated mean, followed by implication of communities in decisions affecting their environment (67.14) and finally sensitize the community and the decentralized collectivity on the great environmental problems to which the community and decentralized collectivity are faced with in the Septandrion zone (54.29). According to Sahel et al., 2014, the outcome of community and decentralized collectivity sensitization in the framework of reforestation is indispensible for the setting up of sylviculture activities in the context of durable management of natural resources.

Values designated or given the same letter has no significant differences at a threshold of 0.05.