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Flora Diversity, Phytosociology and Distribution Pattern of the Woody  Vegetation and Its Relation to Soil Types, in Kalogi District, Nuba  Mountains, Sudan

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Ismail Mirghani Ismail 

Forestry and Gum Arabic Research Centre, Agricultural Research Corporation, Khartoum, Sudan

Corresponding author:  Ismail Mirghani Ismail 

Importance Value Index Contiguous 
Species Richness 
Species Evenness 
Received: 04.10.2023 
Received in revised form: 24.10.2023 
Accepted: 28.10.2023
The work documents the findings of ecological parameters, which have been carried out in the low-rainfall woodland savanna of the Nuba  Mountains, Sudan. Filling the information gap on the woody vegetation along different habitats in Kalogi district. The vegetation sampling and data analysis were done following standard procedures. Forty-five plant species belonging to 29 genera and 14 families have been documented. The most common plant species based on the importance value index are  Dichrostachys cinerea (IVI-98), Vachellia seyal (IVI-28), and Balanites aegyptiaca (IVI-25) respectively in dark cracking clay soil habitat. On the other hand, the most common species on GARDOUD soil habitats are  Hyphaene thebaica (IVI-37), followed by Balanites aegyptiaca (IVI-35),  Combretum hartmannianum (IVI-23), Vachellia oerfota (IVI-20) and Albizia amara (IVI-16) respectively. Fabaceae is found to be the most dominant family. The distribution pattern revealed that 95.6% of species showed contiguous distribution, while 4.4% were randomly distributed. GARDOUD  habitats showed the highest values of species richness and diversity indices as flow: richness of 39 species, Shannon-Wiener’s (H’) (2.77), Pielou index  (E) (.076), Simpson index (D) (0.9), Margalef index (M) (5.9).


Nuba Mountains describes a mountainous region approximately 10° to 12° N, and 29° to 31° E,  surrounded by plains. It is also a region that, for the most part, lies in the federal state of South Kordofan  (Ille, 2015). Nuba Mountains can be classified as one of the richest and most diversified regions in terms of vegetation cover components, beside Jebel Marra in  Darfur, Jebel ElDair in North Kordofan, Ingassana Hills in the Blue Nile, and Red Sea Hills in the Red Sea. 

Kalogi district is where is study is conducted and is located in Gadeer locality which is one of the 16  localities of South Kordofan State. 

The study of plant communities and their classification is termed phytosociology (Mishra et al.  2012; Ahmad and Shaukat, 2012). Phytosociology is useful to describe the population dynamics of each plant species occurring in a particular community and to understand how they relate to the other species in the same community (Mishra et al. 2012). 

The Convention on Biological Diversity (1992) defined  Biodiversity as “the variability among living organisms from all sources including among other things,  terrestrial, marine and other aquatic ecosystems, and the ecological complexes of which they are part; this includes diversity within species, between species,  and of ecosystems. 

Species richness refers to the number of species in a  particular area, whereas species diversity refers to a  combination of richness and relative abundance  (Newton, 2007). A comprehensive review of the methods used for estimating both of these variables is provided by Magurran (2004).  

Lack of information on both taxonomical and ecological regarding the woody vegetation of the  Kalogi district, besides the climatic changes during the last decades, which may change the floristic composition, encouraged to conduct of this study. 

The area is considered one of the most important sources of diversified timber and non-timber forest products to the Sudanese markets.  

This study aimed to fill the information gap on the woody vegetation along different habitats in the  Kalogi district. Furthermore, we expect to have more  Comprehensive and detailed information about these native woody vegetation regarding floristic and ecological aspects. 


Study area 

The study area is located in the Gadeer locality of  Nuba Mountains, South Kordofan. the study area extends from Umdiheileeb village (11° 2’41.56″N,  30°59’7.03″ E) in the north to Morong village  (10°33’29.60″N, 31° 5’36.12″ E) in South and from  Tosi village (10°51’50.22″ N, 30°49’48.10″ E) in the western direction to Gadeer village (10°49’40.02″ N,  31° 7’51.11” E) in the east. The vegetation of the area of this study was classified according to (Harrison and  Jackson, 1958) as special areas of low rainfall woodland savanna. 

Data collection 

Systematic sampling has been carried out with 56  circular plots of 01 ha. covering different sites during the period from Nov. to Dec. 2019. In each plot, all woody plants and individual numbers of each have been recorded. According to soil types, the vegetation of the study area was divided into two vegetation communities: vegetation of dark cracking clay soil and vegetation of GARDOUD soil. 

Data analysis  

Phytosociology analysis 

Phytosociological analysis was conducted for the woody vegetation of the Kalogi district. The density,  frequency, and abundance of each species were measured and values were converted to their relative values to obtain the Importance value index (IVI)  (Curtis, 1959). 

The distribution pattern of the woody species was calculated as abundance/frequency ratio (A/F) as suggested by Whitford (1949) as a measure of contiguousness. The ratio indicates regular (< 0.025),  random (0.025 – 0.05), and contiguous (> 0.05)  distributions (Curtis and Cottam, 1956). 

Diversity indices  

Species diversity, equitability, and concentration of dominance were computed by using Shannon-Weaver  (1949), (Pielou, 1966), and Simpson indices (1949),  respectively. Species richness was obtained as a  number of species an calculated by Margalef’s Index  (1968). Similarity between habitats was obtained by using the Jaccard index (Jaccard, 1912).  

The past 3 packages have been used for data analysis to obtain alpha diversity indices and the Biodiversity Pro 2 package used for calculating the Jaccard index and the past 3 packages have been used for data analysis. 


Floristic composition 

In this study, a total of 45 woody species belonging to  29 genera and 14 families were sampled. The most represented family was Fabaceae with 15 species followed by Malvaceae 6 and Anacardiaceae, and Combretaceae with 5 species for each. Fabaceae is considered one of the dominant and most important families in Sudan (Table 1), it is also recorded as a  dominant family in different studies (Ismail and  ElSheikh, 2016; Ismail, 2020a; Ismail, 2020b). 

Phytosociology analysis 

Density and frequency  

A total of 38 tree species were sampled in garden soil habitats. The absolute density of total woody plant species in GARDOUD habitats was 248.1  stem/ha. The highest relative density was recorded by Hyphaene thebaica (19%) which is frequent in 30%  of sampled plots and Balanites aegyptiaca (19%)  which is frequent in 53.8% of sampled plots followed by Combretum hartmannianum (11%) which frequent in 46.2% of sampled plots (Table 1). 

A total of 30 tree species were recorded from habitats of dark-cracking clay soil. The absolute density of total woody plant species in dark-cracking clay soil habitats was 510.1 stem/ha. 

The highest relative density was recorded by  Dichrostachys cinerea (56%) which is frequent in 75% of sampled plots followed by Vachellia seyal (11%)  which frequent in 46% of sampled plots and Balanites aegyptiaca (7.9%) which frequent in 64% of sampled plots (Table 1). 


The most dominant species in dark cracking clay soil habitat was Dichrostachys cinerea with IVI (98), followed by Vachellia seyal (28), Balanites aegyptiaca (25), Senegalia senegal (22) and Combretum  

hartmannianum (16) (Figure 2). While the dominant species in the GARDOUD soil habitat was Hyphaene thebaica with IVI (37), followed by Balanites aegyptiaca (35), Combretum hartmannianum (23),  Vachellia oerfota (20) and Albizia amara (16) (Figure  3). 

It’s clear that Dichrostachys cinerea dominated species with the highest value of IVI; this may be due to the suitability of dark cracking clay soil habitat to the requirements of this species, in addition to the fruits and leaves of this species is considered as one of the most important sources of fodder for animals during the dry season. This area where species is dominant is considered one of the most important routes of seasonal migration of animals that feed on its fruits, and therefore animals play an important role in spreading their seeds all over the area.  

From the results we found that Balanites aegyptiaca and Combretum hartmannianum are listed as dominant species of both habitats, this assures its ability to live in diversified habitats.  

Flora Diversity, Phytosociology and Distribution Pattern of the Woody  Vegetation and Its Relation to Soil Types, in Kalogi District, Nuba  Mountains, Sudan 23
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Flora Diversity, Phytosociology and Distribution Pattern of the Woody  Vegetation and Its Relation to Soil Types, in Kalogi District, Nuba  Mountains, Sudan 24

Figure 2: Dominant woody species of  GARDOUD soil. 

Distribution pattern 

Among the studied habitats, distribution pattern of all woody species was contiguous (95.6%) except  Terminalia leiocarpa and Combretum aculeatum were random (4.4%) and no species showed a regular pattern. 15 (34.0%) of the species of contiguous pattern were distributed only in the GARDOUD soil habitat and 5 species (11.6%) were distributed only in dark cracking clay soil habitat, while 23 species  (53.5%) of contiguous pattern and the two species of random pattern were distributed in both the two habitats (Table 1). 

From the results, it’s clear that a contiguous distribution pattern was recorded for the majority of species followed by only two species that showed a  random pattern. There was no record of a regular distribution pattern, this may attributed to the absence of severe competition among species; this agreed with the fact that stated by Odum (1971)  contiguous pattern of distribution is common in nature, random distribution is found only in very uniform environment and regular distribution occurs where severe competition exists between individuals.  

Diversity Analysis 

In the study area, species richness and diversity were found higher in the GARDOUD soil habitat as compared to Dark dark-cracking clay soil habitat of the study area.  GARDOUD soil habitat showed higher values in all  diversity indices as follows, Shannon Weiner’s (H’)  (2.77), Pielou index (E) (.076), Simpson index (D)  

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Flora Diversity, Phytosociology and Distribution Pattern of the Woody  Vegetation and Its Relation to Soil Types, in Kalogi District, Nuba  Mountains, Sudan 25

Figure 3: Dominant woody species of soil  dark cracking clay habitats

(0.9), Margalef index (M) (5.9) and richness of 39  species (Figure 2); while habitat of Dark cracking clay soil showed lower values in all diversity indices as follow,  Shannon-Wiener’s (H’) (1.76), Pielou index (E) (.0.52),  Simpson index (D) (0.66), Margalef index (M) (3.99)  and richness of 30 species (Figure 4).

The lowest values of diversity indices may be attributed to intensive human activities such as the continuous expansion of mechanized and shifting agricultural activities in highly fertile and productive dark-cracking clay soil; whereas GARDOUD soil rarely be cultivated by seasonal crops.

The values of diversity indices in dark cracking soil habitat were relatively low due to the dominance of Dichrostachys cinerea with the largest value of IVI, exceeding the values of all species studied, a similar case was stated by Ismail and Alawad (2017). The low evenness value indicates the dominance of the environment by a few species  (Van Breugel et al. 2007). 


The similarity of species between the two studied habitats is illustrated in Figure 5. revealed that 53.3%  of the woody species were shared between the two habitats. This may be due to the suitability of the habitats to the requirements of these species.  Balanities aegyptiaca and Combretum hartmannianum can be considered as the most important species in the study area; especially because they showed dominance in both habitats.  

Table 1: phytosociological parameters and distribution pattern of the studied species 

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Flora Diversity, Phytosociology and Distribution Pattern of the Woody  Vegetation and Its Relation to Soil Types, in Kalogi District, Nuba  Mountains, Sudan 26
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Flora Diversity, Phytosociology and Distribution Pattern of the Woody  Vegetation and Its Relation to Soil Types, in Kalogi District, Nuba  Mountains, Sudan 27
image 24
Flora Diversity, Phytosociology and Distribution Pattern of the Woody  Vegetation and Its Relation to Soil Types, in Kalogi District, Nuba  Mountains, Sudan 28

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Figure 4: Richness and diversity indices of the two studied habitats Figure

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5: Dendrogram showing the percent of similarity between studied habitats.


The woody plants cover a diversity of the studied area and were represented by 45 plant species belonging to 29 genera under 14 families. While the dominant family Fabaceae is represented with 15  species, 7 families are monotypic. Dichrostachys cinerea showed the maximum IVI values at habitats of dark-cracking clay soil and the whole study area.  The habitats of GARDOUD soil the more diverse than those of dark-cracking clay soil. 


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