Structural and Demographic Characterization of Crête-Brûlée Forest Species, 4th Mirebalais Municipal Section, Haiti

Where PJ is the Jaccard coefficient of floristic similarity.
a: the number of species from the list in medium a.
b: the number of species from the list in middle b.
c: the number of species common to the two environments [11].

Inventory of forest species

Analysis of the floristic data from the 15 plots at Crête-Brûlée showed that the flora has a specific richness of 40 species grouped into 39 genera and 24 families. It appears from Table 1 that the most represented families are the Fabaceae with 11 species which accounted for (27.5%) of the total number (40 species), the Meliaceae with 4 species which represent (10%), the Anacardiaceae, the Bignoniaceae and Myrtaceae each with 2 species which showed a percentage of 5% each of the aforementioned families. And finally, other families such as Burseraceae, Bombaceae, Euphorbiaceae, Capparaceae, Apocynaceae, Moraceae, Urticaceae, Malvaceae, Simarubaceae are represented by a single species.

Table 1: Distribution of botanical families and species encountered at Crête-Brûlée.

The density of forest species

The actual density (Dr) for trees whose diameters are >3cm (Table 2), we obtained densities which vary from 30±85 trees/ha. It was also noted that TS1 has better actual density compared to other transects. On the other hand, for the regeneration density (Nr) or of the stems of the future, those with diameters <3cm, the variation was made at the level of the three transects of 0.025±0.64. TS3 was found to have better regeneration density than other transects.

Table 2: The density of the forest diversity.

Diameter of forest species in TS1

The TS1 has passed through several localities, it leaves from La Bastille to reach Bois l’Etat via Décès, Trianon, Nogode, Crête- Brûlée, Manyan, Saintonge, Bois Marseille and Dejalus. Analysis of the histogram in Figure 1 showed a predominance of trees of diameter class [10 20] which accounted for 21.83% of the 229 trees. Trees recorded at the level of 5 plots followed by class [20 30] which represents 18.77%.

Figure 1: TS1 Stems diameter class.

Diameter of the forest species in TS2

The localities forming TS2 are: Lavelanèt, Meye, Dosan, Bresète, Loss and Domon. It was observed in Figure 2 that in the previous localities that the rods of the diameter class [10 20] are in the majority. For the 193 trees listed, 57 are in this class, it showed a percentage of 29.53%. In contrast, Diameter class [80 90] with only 2 shafts is the class that contains the smallest amount of shafts for TS2. It occupied only 1.04% of the total workforce.

Figure 2: TS2 stems diameter class.

Diameter of the forest species in TS3

The TS3 started at Cholette to end at Calebasse via Debrica, Sens, Laou, Morne Lae, Merson, Barot Calavène. Figure 3 showed a preponderance of trees in the diameter classes [10 20] and [20 30] for a respective value of 65 and 75 trees which represents 28.63% and 33.04% of the 227 trees listed for TS3. The least badly endowed class is that of [80 90] with 0 individuals. It was also found as the diameter classes increase the trees of large diameters decrease.

Figure 3: TS3 stems diameter class.

TS1 forest species height class

It was observed in Figure 4 that the height classes of TS1 showed a predominance for trees of the classes of [5 10], [30 35] which represents 18.50% of the total population. Trees that are shown in small quantities are found in the height classes [35 40], [40 45], [45 50].

Figure 4: TS1 tree height class.

TS2 forest species height class

Examination of Figure 5 showed that the dominant height class of TS2 is that of [10 15] which had a proportion of 28.74%. It was also found that the height classes [5 10], [15 20] counted the same quantity of trees which shows 17.37%. Finally, we noticed an almost zero presence of trees in the classes [35 40], [40 45] and [45 50].

Figure 5: TS2 tree height class.

TS3 forest species height class

The most dominant height classes of the Figure 6 are respectively. [20 25], [10 15]and [15 20]. The weakest represented class is that of the class [0.5 5].

Figure 6: TS3 tree height class.

Analysis of Table 3 showed that the overall Shannon-Weaver index is 3.09 bits. While for the transects, TS1 has an index of 2.59 bits, it records the high rate of diversity among the transects. Then, TS2 accuses an index of 2.49 bits. Finally, for TS3, an index of 2.19 bits is noted.

As for Piélou’s fairness overall, it is 0.87. However, for the transects it follows the same trend as the Shannon index. TS1 has the highest fairness with 0.79 and again TS3 has the lowest fairness with 0.71.

Table 3: Shannon-Weaver index & fairness of Pielou.

Jaccard similarity index (PJ) of transects

Examination of Table 4 showing the Jaccard similarity index for the transects showed that this index is between 14.28±21.43. TS1 and TS3 have the highest similarity rate.

Table 4: Jaccard similarity index results.

Hamming similarity coefficient (H)

Analysis of Table 5 showed that the Hamming distance of the transects varied from 79.57±85.72. TS1 vs TS2 has the longest distance.

Table 5: Hamming similarity coefficient results.

The floristic inventory of woody trees through the 15 plots in the 4th communal section of Mirebalais revealed a partial specific richness of 40 species divided into 39 genera and 24 families. The families best represented by the number of species are Fabaceae (11 species), Meliaceae (4 species), Myrtaceae, Bignoniaceae and Anacardiaceae with each of 2 species. Our results agree with those found by [12]. This numerical importance of fabaceae could be explained, in part, by their mode of dissemination. And all the more so, for [13] fabaceae are fast growing species and they have the particularity of living in symbiosis with bacteria installed in root nodules and facilitating the assimilation of atmospheric nitrogen. Thanks to this property, fabaceae can survive and compete effectively in nitrogen-poor soils.

The horizontal structure revealed a negative exponential distribution which is characterized by a small number of large diameter trees and small diameter trees are the majority. Our results are similar with [14]. This can be explained by the result of strong pressure to harvest wood. Because the repeated cuts of wood and the accumulated water deficits do not allow the vegetation to reconstitute itself quickly. According to, [15] disturbances cause changes in the structural characteristics of stands, diameter is one of the most impacted parameters.

With regard to the vertical structure of forest species, it is observed beyond 30m that the trees are poorly represented. The low representativeness of tall trees could result in anthropogenic disturbances to which is added the pauperization of agriculture in the section. For [16], the tree becomes a growing savings by playing a role similar to that of large livestock by providing one-off income for major expenses as well as fuel for family consumption or for sale.

The low density of trees per hectare observed, whether real or regenerative, can be explained by anthropogenic factors such as wildfire, agriculture, livestock, cutting/timber, coal mining and natural disturbance such as drought. Agriculture and logging dramatically contribute to the reduction of plant cover.

The most frequent species in the study area are: Macrocatalpa longissima, Cassia siamea, Haematoxylon campechilanum, Cedrela oradata and Schaefferia frutescens. These dominances can be explained from an economic point of view because when you reach maturity you can earn a lot more money than cutting it down at an early age, especially for Macrocatalpa longissima, the wood of which is highly valued in the industry furnishings in Haiti.

During this study a rigorous examination of the various indices of diversity made it possible to detect the degree of diversity or the stability of the 4th section. To begin with, the overall Shannon index is very strong for the entire section while at the level of the 3 transects we could observe that this index is weak. According to [17], only a few species are the most dominant in the section. Fairness is medium, according to the assertions of [18] when the equity index of an ecosystem or a plant formation exceeds 70%, this implies that competition is relatively low between species. This threshold represents an equi-distribution of species, in other words and there is no dominance between forest species. The Jaccard similarity index revealed a dissimilarity at the level of the transects while for the Hamming distance the transects are highly or very highly diverse.

From the results obtained during this study which consists of the structural and demographic characterization of forest species in Crete-Brulee, we can draw the following conclusions:

A. The partial floristic richness of the section is 40 species divided into 39 genera and 24 families. The fabaceae family and the myrtaceae are the most dominant.

B. The actual density varies from 30±85 trees/ha-1 and the regenerating density in turn oscillates between 0.025±0.64 trees/ha-1. These densities are very low due to natural and human disturbance.

C. The diameter class distribution showed that individuals of small diameters are in the majority and the vertical structure, on the other hand, showed that tall trees are rare.

D. Frequency analysis determined that the following species are the most dominant in the section: macrocatalpa longissima, Cassia siamea, Haematoxylon campechianum, Schaefferia frutescens and Cedrela oradata.

E. The Shannon index varies from 2.19±2.59 bits but the fairness showed an average equipartition of the species at the level of the transects, it oscillates between 0.71±0.79. However, the comparison of the transects with the Jaccard similarity index revealed that the transects have a low similarity rate between 14.29±21.43 and the Hamming distance showed a strong and very strongly diversified floristic difference which varies between 79.57±85.72. These results show that despite natural and human disturbances, woody forests show a certain resilience. However, other complementary studies deserve to be made in the section on the detrimental effects of deforestation on infrastructures downstream of the watersheds, ethnobotanical and soil studies would make it possible to better select the plant material according to the abiotic constraints (salinity, acidity, water stress), in order to better understand the expectations and concerns of farmers in the 4th section so that they can be integrated into reforestation projects.

The authors are grateful to Ministry of Agriculture, Natural Resources and Rural Development of Haiti, Central Public University of Haiti, University, Central of the Americas of Haiti and University of Guadalajara for supporting the project; to Marilyn Z.R.G. h., Lovren A. R.G. h. (RIP) for being an indirect part of the project.

Authors Vincent, Ruiz-Blandon, Gallegos-Rodríguez and Hernández-Álvarez, designed the study, performed the statistical analysis and wrote the first draft of the manuscript. Authors Felix, Lafelur and Barthélemy, managed the analyses of the study and literature searches. All authors read and approved the final manuscript.

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