The study was conducted in the central Gondar zone (residents) of the Gondar Zuria District, which is situated in Teda kebele in Maksegnit woreda. It is specifically 24 km and 697 km away from Gondar city and Ethiopia’s capital, Addis Ababa, respectively in Fig. 1. The area is categorized under the Woyna dega agro climatic zone and the annual temperature ranges between 25–30 °C whereas annual rainfall distribution is estimated around 1500 mm.

Figure 1. 

Map of the study area.

Data for this study were gathered using a systematic sampling strategy with a random starting point. Sample plots were selected at regular intervals, ensuring that the sample was evenly distributed throughout the research area. This sampling method was chosen for its ease of use, ability to sample the intended area, and capacity to collect samples across environmental gradients such as elevation. Systematic sampling proved to be more effective for addressing these research questions (Jordan et al. 2011). The first transect line was established 20 m within the forest, running parallel to the contour line. Systematic sampling was conducted at 50-meter intervals along this transect, resulting in two transect lines with seven circular sampling plots each, while the other transect line contained five sampling plots. Along each transect line, the circular plots had a radius of 6.5 m for trees. The regeneration status, species biodiversity, woody species structure, and species composition at the Kies Diba botanical garden were evaluated using saplings measured at 4.5 m and seedlings at 2.5 m. Additionally, sub-plot measurements were laid out, with one in the center and four at each corner of the quadrant, totaling five sub-plots per quadrant for counting seedlings and saplings. In the forest, a total of 60 sampling sub-plots were created across 12 quadrants.

Two parallel transect lines, 50 m apart, were employed in every forest. The first quadrat was arranged randomly at the base of the first transect line. The Diameter at Breast Height (DBH) of all woody species taller than 1.3 m was measured with a vernier caliper to identify seedlings. The DBH of woody species with branches approximately 1.3 meters above the ground was individually measured and recorded. Woody species below 1 m in height with a DBH of less than 2.5 cm were classified as seedlings, while those over 3 m in height with a DBH of less than 2.5 cm were categorized as saplings (Sobol et al. 1996). The number of seedlings and saplings in each plot was recorded to assess plant regeneration. The heights of these species were measured using a meter tape and a long, uniform pole marked at 0.5-meter intervals (Nemarundwe and Richards 2012). When using these methods was impractical, visual estimates were employed. The design and layout of the circular plots utilized in the sampling area are presented in Fig. 2 below.

Figure 2. 

The design of a sample circular plot of the study area.

Key informants who were familiar with the local names of all the woody species found in each plot were chosen among the neighboring students and had a great deal of expertise. The specimens were recognized by Leaf Span apps and cached by cameras in order to get their scientific designation. Following that, the specimens were identified by cross-referencing them with previously identified specimens in Ethiopia’s national herbarium and by consulting published books on the flora of Ethiopia and Eritrea (Friis 2014).

In the botanical garden, the regeneration status of sample species was examined by contrasting seedlings with young saplings and young saplings with old trees (Shankar 2001; Dhaulkhandi et al. 2008; Tiwari et al. 2010) in the following categories: 1) good regeneration, if a species is present in seedlings > saplings > mature trees; 2) fair regeneration, if a species is present in seedlings > saplings < mature trees; 3) poor regeneration, if a species is present only in the sapling stage and not as seedlings (saplings may be less than, more than, or equal to mature); 4) none, if a species is present as mature but absent from both sapling and seedling stages; and 5) new, if a species is present only in sapling and/or seedling stages and not in mature trees.

Diameter at Breast Height (DBH): Eight DBH classes (i.e., 10–20 cm, 20.1–30 cm, 30.1–40 cm, 40.1–50 cm, 50.1–60 cm, 60.1–70 cm, 70.1–80 cm, >80 cm) were used to investigate the structural data of DBH (Hundera et al. 2007). A plant’s basal area is the outline of its vicinity to the earth. It is given as square meters per hectare (Mueller et al. 1974).

Basal area (cm²) = ∏ × d² (1)

where, π = 3.14 and d = DBH (cm)

$\text{D}\left(\text{density}\right)=\frac{\text{number of above-ground atems of species counted}}{\text{sample area in ha}}$ (2)

$\text{RD}\left(\text{relative density}\right)=\frac{\text{desity of species A}\times 100}{\text{total density of all species}}$ (3)

The likelihood or chance of discovering a species in a particular sample area or quadrat is known as frequency. The size of the quadrats, the size of the plants, and the patterns in the vegetation all play a role (Kent and Coker 1992).The following formula was used for calculation:

$\text{Frequency}=\frac{\text{the number of plots where that species occurs}\times 100}{\text{the total number of plots}}$ (4)

$\text{Relative frequency}=\frac{\text{the ferequency of species A}\times 100}{\text{the total number ferquencies}}$ (5)

Index of Importance Value (IVI): It incorporates information on three dimensions: relative frequency, relative density, and relative abundance. Alternatively, it frequently illustrates the degree of a particular species’ dominance, occurrence, and abundance in relation to other related species in a region (Kent and Coker 1992).

IVI = Relative density + Relative frequency + Relative dominance

$\text{Dominance}=\frac{\text{total basal area}}{\text{area sampled in ha}}$ (6)

$\text{Relative Dominance}=\frac{\text{the dominance of species A}\times 100}{\text{total dominance of all species}}$ (7)

The diversity index of Shannon, which changes based on the number of species present, was used to examine the diversity within the research area. More species mean a higher value, which denotes better diversity. After that, the Shannon-Weiner diversity index (H’) was computed (Kent and Coker 1992).

H’ = ∑^s_i=1 = pi × lnpi (8)

Where: S = total number of species; pi = relative frequency of species; Ln = natural logarithm; H’ = Shannon-Weiner Index of Diversity.

The Simpson’s index of diversity

D = 1 − ∑ⁿ⁻¹ (9)

Where n is the total number of individuals across all species, and n is the total number of creatures of a certain species.

The variety of plant species found in the research area is shown in Table 1. Based on the findings, 16 plant species from 13 families were identified in the study region, out of a total of 478 unique plant species that were observed. The results of this investigation showed that the Shannon Weiner Diversity Index and the Simpson Diversity Index had respective values of 1.6 and 0.64. In general, tropical forests have higher species diversity (Kent and Coker 1992). Seldom does the Shannon-Wiener diversity index rise above 4.5, typically falling between 1.5 and 3.5 (Mueller et al. 1974). The study site’s species diversity, as determined by the Shannon-Weiner (H’) index, was found to be 1.58; hence, the result in our study area falls between 1.5 and 3.5 for tropical forests, but this value shows the species diversity is included in the low biodiversity range unless they managed well from disturbance because this value meets the lower limit requirement of the range of tropical forest, and if not well managed, this botanical garden falls short of the normal range value of the Shannon-Weiner index.

Furthermore, because the sample plot is circular in shape rather than rectangular or square, it may underestimate the species diversity value, making it difficult to generalize about the diversity of woody species in the site. For this reason, the type of sample plot is important when determining the species diversity of the study area. Diversity declines as the Simpson Index rises, and the index becomes less responsive to species richness and significantly biased in favor of the most prevalent species in the sample (Magurran 2004). Compared to Chunati Wildlife Sanctuary (0.056) (Hossain 2014) and Dudhpukuria-Dhupachori Wildlife Sanctuary (0.0192), the research area’s Simpson Diversity Index value was (0.64) greater (Hossain et al. 2013).

Species composition and species richness are important indicators for assessing biodiversity (Husch et al. 2002). Based on this study, Fig. 3 shows the range of plant species among different families in the Kies Diba Botanical Garden. The family of Leguminosae had three species; the family of Fabaceae had two species; and the rest of the nine families had an equal distribution of plant species, with one species for each family. It was tried to see the species composition of the site; there were a few species, but only 16 plant species were found. A high number of individual species are found in the Leguminosae family, followed by the Fabaceae family.

Figure 3. 

Plant species distribution among families.

For a particular species, the recruitment processes and general trends of population dynamics are shown by the patterns of diameter class distribution (Steininger 2000). Analysis was done on the distribution of trees within the various DBH classes. There were four classes assigned to the DBH: 0–10 cm, 10.1–20.0 cm, 20.1–30.0 cm, and 30.1–40.0 cm are the first four ranges. The first DBH class (0–10 cm) contains the majority of the tree individuals, and as the size of the DBH class grows, the number of people steadily declines towards the upper DBH classes. The diameter-class distribution of plant species in the sample region can be used to infer the population structure of woody species based on data gathered in the field. The woody species structure in Fig. 4 resembles an inverted J-shape, suggesting either a pattern where species frequency distribution has the highest frequency in the lower diameter classes and a gradual decrease towards the higher classes, or a general trend of decreasing plant species when there is an increase in the diameter of tree species in the botanical garden. The pattern of this botanical garden resembles an unhealthy forest, as seen by the diameter class distribution of plants for the research site.

Figure 4. 

Diameter class distributions of species.

The degree of dominance and abundance of a particular species relative to other species in the area is a significant value index (Kent and Coker 1992). Table 2 displays the outcome of the IVI, which is derived from the relative density, relative basal area (relative dominance), and relative frequency of woody species. An important metric that establishes conservation priorities and indicates a species’ ecological significance in a particular ecosystem is the IVI value (Lamprecht 1989). It makes it possible to rank the species in order of importance for management and conservation initiatives; those with the lowest IVIs may benefit from these efforts (Shibru 2002). The output of the IVI analysis showed that Mytenus arbutifolia 99.75 (33.2%) was the first among the four most dominant plant species, such as Acacia nilotica 46.93 (15.6%), Acacia seyal 42.08 (14%), and Carissa edulis 34.7 (11.5%) in the botanical garden (Table 2). These species constituted around 74.3% of the total the important value index was less than 20, and the bulk of the species, or roughly 25.7%, had a value of less than 20 in (Fig. 5). 6.25% of the species throughout the various IVI classes were less than 1, 25%, according to the distribution of species. 37.5%, 5.1–10.0, 0%, and 1.1–5.0 10.1–15.0, 6.25 percent. The research botanical garden exhibited significant value indices for 15.1–20.0 and 25% greater than 20.0.

Figure 5. 

Important Value Index class and distribution of woody plants.

The potential regenerative state of individual species within a forest stand in space and time determines the future composition of the forests (Henle et al. 004). A population’s ability to regenerate successfully is indicated by its population structure, which is defined by the existence of a sufficient number of seedlings, saplings, and adults (Saxena and Singh 1984). The presence of saplings beneath the canopy of adult trees also suggests how a community will look in the future. The regrowth of many plant species is influenced by biotic intervention and climate variables (Henle et al. 2004; Dhaulkhandi et al. 2008). In the circular plot of the sample in the Kes Diba Botanical Park, it was found in this study that 6.25% of tree and shrub species had acceptable regeneration status and 25% had poor regeneration status. In the Kes Diba botanical garden, 56.25% of plant species that were only available as saplings or seedlings were regarded as new, while a total of 25% of plant species were not regenerating at all. Tessaria integrifolia was the species with a fair rate of regeneration, while the species that were found to have a poor rate of regeneration were Clutia abyssinica and Acacia. The species that were found in the non-regenerating category were Acacia seyal, Pterolobium stellatum, Croton macrostachyus, and Olea africana. New regenerating species include Mytenus arbutifolia, Plectranthus lanunginosus, Aloe berhana, Carissa edulis, Jasminum officinale, Carduus nyassanus, Capparis tomentosa, Calpurnia aurea, and Anagyris fooetida, as shown in Table 3 and Fig. 6.

Figure 6. 

Regeneration status of plant species.