Floristic Composition, Structure, and Regeneration Status of Woody Plants in Wonjeta St Micheal Church Forest, Northwestern Ethiopia

The study was conducted in a historian Wonjeta St Michael Church Forest, believed to be constructed in 11th century in Northwestern Ethiopia. The composition, structure, and management of this forest is not documented. Fifty plots of 20 m × 20 m (400 m2) were laid along five-line transect for vegetation data collection. In addition, 5 m × 5 m subplots were laid within the main plot to sample seedlings and saplings. All plots were laid at a distance of 50 m along the transect lines. The diversity and population structure of woody individuals of trees and shrubs with a diameter at breast height (DBH) ≥ 2.5 cm and height ≥2 m were measured, and DBH <2.5 cm and height <2 m were counted as seedlings and saplings. All trees and shrubs recorded in the 50 plots were used for vegetation structure analysis. A total of 65 woody plant species in 53 genera and 33 families were recorded. Out of the total number of species, three were found to be endemic to Ethiopia. The family Fabaceae had the highest number of species, followed by Moraceae, and then Euphorbiaceae with 14, 6, and 4 species, respectively. The results of Shannon Wiener diversity and evenness indices of woody species were 2.8 and 0.68, respectively. Woody species densities for mature individuals were 2,202.5 stems ha−1, seedling 2419.2 stems ha−1, and sapling 1737.6 stems ha−1. Priority for conservation should be given using population structure, important value index, and regeneration status as criteria. Results of the structural analysis revealed that the Forest is highly dominated by small-sized trees and shrubs indicating that it is in the stage of secondary development and there are species that require urgent conservation measures.


Introduction
Tropical forests are biologically diversifed ecosystems with high species richness, evenness, net primary production (NPP), and biomass accumulation due to prevailing favorable environmental conditions [1]. Tey are, however, highly threatened by anthropogenic activities [2]. Deforestation is still alarmingly high in the tropical region resulting formation of small patches of fragmented forests [3]. Loss of forest cover and biodiversity due to anthropogenic activities is a growing concern in many parts of the world. Africa's forest cover is estimated to be 650 million hectares constituting 17% of the world's forests including several global biodiversity hotspots [4].
Ethiopia is one of the top 25 biodiversity-rich countries in the world and hosts two of the world's biodiversity hotspots, namely, the Eastern Afromontane and the Horn of Africa hotspots. It is also among the countries in the Horn of Africa regarded as the chief Centre of diversity and endemism for several plant species. Te Ethiopian fora is estimated to have about 6000 species of higher plants, of which 10% have considered to be endemic [5]. Woody plants constitute about 1000 species [6]. Tis richness in biodiversity is due to topographical diversity with fattopped plateaus, high mountains, river valleys, deep gorges, rolling plains, and variation of altitude ranging from 116 to 4620 meter above sea level (m.a.s.l.) [7]; (IBC, 2014).
Many scholars also agree that the forest of Ethiopia is decreasing from time to time due to anthropogenic activities [8,9]; lack of integration of the local people living around the conservation areas is the major constraint to the overall conservation efort in Ethiopia [10]. Due to this, it has now realized that unless the local community is involved in the conservation efort, the sustainability of forest resources will be under question. Rapid human population growth, poverty, forest clearing for cultivation, overgrazing, exploitation of forests for fuel wood, and construction materials without replantation and lack of proper policy framework are some of the factors that contribute to the loss of forest resources in Ethiopia [11,12]. Reduction in forest cover has several consequences, such as soil erosion and reduced capacity for watershed protection with possible fooding, reduced capacity, and loss of biodiversity. Tis leads to the instability of the ecosystem and reduced availability of various forest products and services [13].
Ethiopia's northern and central highlands are nearly devoid of forests due to deforestation and environmental degradation, where forests remain as small, isolated patches always on the tops of mountains and heads of streams surrounding churches [14]. Tese remnant natural forest fragments persist because of their sacred status under religious knowledge of forest conservation of the Ethiopian Orthodox Tewahido Churches (EOTC) [14,15].
Wonjeta St Michael Church Forest is one of the few reminant natural forests in the Ethiopian upper Blue Nile basin, where most of the forest area has degraded and converted to agricultural land due to demographic pressure, sedentary farming, and exotic tree plantation. Despite of all these, Wonjeta St Michael Church Forest is not yet studied. Tese inspired researchers to study the vegetation status, woody species composition, density, diversity, vegetation structures, and regeneration status of the forest. Terefore, this study aimed to describe the opportunities and challenges of such Church forest for the upper Blue Nile basin and ecosystem wellbeing.  [16].

Materials and Methods
Five-line transects were laid parallel to each other and 50 m apart.
Te frst line transect was started 50 meters inward from the edge of the forest to avoid "edge efect" [17,18]. Along each transect, sample plots having an equal size of 20 m × 20 m (400 m 2 ) were laid at distance of 50 m from each other. A total of 50 plots were laid for woody species data collection. Within the main plot, 5 m × 5 m subplots were laid at four corners and one in the middle for seedling and sapling data collection.

Vegetation Identifcation and Data Collection.
All woody plant species encountered in each plots were identifed and recorded with structural and abundance data. Identifcation of those plant species were carried out by their local (vernacular) name using experienced key informants and taxonomist. For those species difcult to identify in the feld, their voucher specimens were collected, and the specimens were brought to Bahir Dar University herbarium for taxonomic identifcation and by referring published volume of the fora of Ethiopian and Eritrea [19][20][21].

Structural Data Collection.
Te diameter at breast height (DBH) and height of woody plants was recorded with measuring tape and calibrated stick, respectively, which were used for description of vegetation structure (frequency, dominancy, basal area, and important value index).
In each plot, trees and shrubs with height ≥2 m and DBH ≥ 2.5 cm were measured and recorded at about 1.35 m from the ground. For trees and shrubs that were branched around the breast height, the circumference was measured separately and averaged. For the purpose of regeneration assessment, from the fve subquadrats, the seedlings and saplings were counted for each species. In this study, a seedling was considered as woody individual with a DBH < 2.5 cm and less than 1 m height; a sapling was considered as those woody individual with a DBH ≥ 2.5 cm and a height of less than 2 m.

Vegetation Composition and Structure Data Analysis.
Te structural parameters were analyzed using the following formula: Basal area of a tree � π(DBH/2) 2 Where π � 3.142, DBH (diameter at breast height) � (C/π). (1) Importance value index (IVI) analysis is used for setting conservation priority. It combines data for three parameters (relative frequency, relative density, and relative abundance) or it often refects the extent of the dominance, occurrence, and abundance of a given species in relation to other associated species in an area [22].
Te vertical stratifcation of species in the study area was examined using the IUFRO classifcation scheme [23]. According to this scheme, tree with >2/3 height of the top represents upper story, trees with height between 1/3 and 2/3 of the top height represent the middle story, and the lower story is represented by trees with height <1/3 of the top height.

Regeneration Data Analysis.
Regeneration status of the forest was analyzed by comparing saplings and seedlings with the matured trees according to Dhaulkhandi et al. [24] and Tiwari et al. [25]; i.e., good regeneration, if seedlings > saplings > adults; fair regeneration, if seedlings > or ≤ saplings ≤ adults; poor regeneration, if the species survives only in sapling stage, but no seedlings (saplings may be <, > or � adults); and if a species is present only in an adult form it is considered as not regenerating.

Measurement of Species Diversity Indices.
Shannon-Wiener diversity index is used to evaluate the species diversity of the study area. It is popular measure of species diversity and evenness that is not afected by sample size as follows: Pi(ln(Pi)).
H′: Shannon diversity index, S: the number of species, Pi: the proportion of individual woody plant species, and ln: is the natural logarism.
Te equitability or evenness of the species in each plot was computed using the following formula: where J: Evenness, H′: Shannon diversity index, and H′max: lnS; S: the number of species. Equitability assumes a value between 0 and 1, where 0 indicates the abundance of few species and 1 indicates the condition where all species are equally abundant.

Woody Plant Species Composition.
A total of 65 woody plant species in 53 genera and 33 families were identifed from Wonjeta St Michael Church Forest. Among the 65 recorded woody species 32 (49.23%) were shrubs, 29 (44.62%) were trees, and 4 (6.15%) lianas ( Figure 2). Te results of the study revealed that the species richness of the forest was higher than some dry afromontane forests of Ethiopia such as Ambo State Forest with 58 species located in South Gondar Zone [26], Wanzaye natural forest with 49 species in South Gondar [27], and Wogello natural forest 20 species in North Gonder [28] and less than many dry afromontane Forests such as Woynwuha Natural Forest with 69 species in East Gojjam [29] and Chebera Churcura National Park with 106 species in Southern Ethiopia [30].

Species Diversity and Evenness.
Te results of Shannon-Wiener diversity and evenness indices of woody species were 2.8 and 0.68, respectively, which means woody diversity and evenness was high when compare to Yegof forest 2.26 and 0.57, respectively [33]. However, the forest has lower value of diversity and evenness indices than Zegie forest (H′ � 3.72 and J � 0.84), respectively [34], and Keja Araba and Tula forest (H′ � 2.81 and 3.14 and J � 0.79 and 0.86), respectively [35]. According to Kent and Coker [22], the Shannon-Wiener diversity index normally varies between 1.5 and 3.5 and rarely exceeds 4.5. High diversity when it is above 3.0, medium when it is between 2.0 and 3.0, low between 1.0 and 2.0, and very low when it is smaller than 1. Te equitability (evenness) index has values between 0 (a situation in which the abundance of all species are completely disproportional) and 1 (all species are equally abundant) [22]. Te study forest has medium diversity may be due to harvesting of fuel wood such as selective cutting, Eucalyptus plantations for timber, or frewood make the forest monocultures leading to homogeneous forests. Te clearing of shrubs/trees for agriculture in the study area could also make the forest into isolated small fragments. Te main reason for this forest to have medium or low evenness (with a few species dominate) could be because of variable environmental conditions, competition between species, overexploitation of some species, rate of dispersal, growth, and recruitment performances [36]. Te diversity and evenness indices imply the need to conserve the forests from human disturbance.  (7)  According to the result, the densities of tree individuals of Wonjeta St Michael Church Forestwith DBH between 2.5 and 10 cm and between 10 cm and 20 cm, and with DBH > 20 cm were 1950.5 ha −1 , 221.5 ha −1 , and 30.5 ha −1 , respectively. Te ratio of density of individuals of Wonjeta St Michael Church Forest with DBH > 10 cm to DBH > 20 cm is very high (7.26). Te comparison of the density ratio of the study site with other 4 forests' density ratio in Ethiopia is given by Table 2. Te ratio a/b indicate that Wonjeta St Michael Church Forest has more tree in lower DBH classes than in the higher classes when compared to Gedo, Menna Angetu, Chilmo, and Menagesha Forest. Te reasons behind these are geographical location, the nature of the forest, altitude variation, age of the forest, degree of conservation, and exposure to disturbance. Te DBH class distribution of all individuals showed inverted J-shape distribution pattern which means that the majority of the species had highest number of individuals in the lowest diameter class. Tis means form the potential source of recruitment to successively increasing diameter classes that ensures sustained future regeneration of the forest if it will be properly managed. However, the density was decreased as DBH class increasing. Tis indicated that the predominance of small and medium sized individuals in the Forest such as Carissa spinarum, Calpurnia aurea, Maytenusobscura, Grewiaferruginea, and Capparistomentosa. Tis could be attributed to high rate of regeneration but poor recruitment in the forest, which might have been caused by unsustainable exploitation of woody species in the forest by the local people some years before maturity.   other the density of individuals were decreasing i.e., large proportion of woody plant species were distributed in the lowest height class. Tis clearly tells the dominance of smallsized individuals and the presence of high regeneration but lower recruitment and absence of matured individuals. It might be due to anthropogenic factors.

Frequency.
Based on the percentage frequency value, the result showed there are eight most frequent woody species in the study area ≥56% (Table 3).

Population Structure.
In the present study, the general patterns of DBH distribution of the forest showed an inverted J-shape distribution pattern. However, some groups of individuals showed population dynamics and recruitment processes for a given species. Te frst type of pattern was inverted J-shape. It shows a high number of species in the lower DBH classes and reduction at the highest DBH classes. Tis pattern was exhibited by the species Pittosporum viridiforum ( Figure 5(a)). Such pattern shows normal or healthy structural pattern with good reproduction and recruitment capacity of a given species [40]. Te second type of population pattern was bell shaped and is characterized by the species Croton macrostachyus (Figure 5(b)). It shows a fairly high number of individuals of the species in the middle DBH classes but lower numbers of individuals of the species in the lower and higher DBH classes. Tis species has poor recruitment potential which might be due to intense competition between the other species found in its surroundings and also were use of this tree for making fencing, charcoal and other purposes. Te third type of population pattern is represented by Senegalia persicifora (Figure 5(c)). In such pattern, the density of individuals increases with increasing DBH up to some point and then decreases with increasing DBH. Te pattern continues with decreasing to some extent and increasing density as DBH increases. Tis population structure pattern showed irregular or zigzag type of distribution and is not healthy because of selective removal of the species for construction and fuel wood.  [40], the high dominance and/or abundance of a few species in a forest could be attributed to a number of  Scientifca factors, such as the overharvesting of the desired species, disturbance factors, succession stage of the forest, and/or survival strategies of the species.

Vertical Structure (Over Story) of St Michael Church
Forest. Te vertical stratifcation of the tree in the study area was examined using IUFRO classifcation scheme [23]. Based on this scheme, the top height was used for the vertical structure of tree. According to the result of the study trees with 2/3 of the top height (height above 24 m) represent upper story is 0.18% of the individuals; trees with height between 1/3 and 2/3 of the top height represent middle story contains 9.35% of the total individuals, and trees with height <1/3 of the top height represent lower story includes contains 90.47% of the individuals (Table 5). Te highest tree distribution in the study area is the lower story class. Tis implies that the forest has been heavily infuenced by the local anthropogenic activities through selective logging for fuel wood, construction, and illegal wood harvest for timber production. Currently, there were some long trees and short to medium individuals. Te dominance of short-heighted individuals was the attribute of good regeneration but low recruitment.

Regeneration Status.
Te result found the total densities of seedling, sapling, and mature plants of the forest were 2419.2 ha −1 , 1737.6 ha −1 , and 2202.5 ha −1 , respectively. Out of the total analyzed tree and shrub ffteen (15) species   Te ratio analysis of woody species seedling to mature individuals in the forest gives that (1.10 : 1), seedling to sapling was (1.39 : 1), and sapling to mature (0.79 : 1). Te result showed that there is more seedling than that of sapling and mature individuals implying the survival of seedling to reach sapling stage and according to Tiwari et al. [25], the forest is now in a fair regeneration. However, there are also species with no seedling and sapling that may be caused by due to the physical condition of their microhabitat and human impacts and need urgent measurement to be taken as they are in poor regeneration. low IVI value that need urgent feedback to regenerate. Te possible reason for this could be either the selective cutting of these species by the local people or unfavorable microhabitat conditions. Tese indicate that as a whole conservation and management of the forest are required. Finally, the accepted manuscript has been deposited on a preprint server [44] as per the stated recommendation during the acceptance e-mail from Sci-enti<ca to the corresponding author.

Conclusion.
From the result of species composition, coverage, and abundance of woody plants, the area will have a more complex and healthier community with a better environmental condition. Tis revealed that the forest can serve as in-situ conservation site. In this study, the result showed that the Forest is dominated by small-sized tree and shrub species, indicating that the Forest was seriously exploited and afected in the previous periods, but currently good regeneration is shown.
Based on structural description of diameter and height class distribution on St Michael Church Forest both DBH and height class shown similar trend, in that the density of tree and shrub species decrease with increasing DBH and height classes, which implied predominance of small-sized individuals in the lower classes than the higher diameter classes indicating good reproduction potential and rare occurrence of large individuals.
Te analysis of frequency class in St Michael Church Forest showed that the higher percentage number of species in the lower class than in the higher frequency classes. Tis indicates that the Forest is foristically heterogeneous.
From the analysis of structures of some selected tree species in the study site, it can be concluded that some species such as Vachellia sieberiana, Senegalia venosa, Acokanthera schimperi, Albizia gummifera, Entada abyssinica, Erythrina abyssinica, Ficus sycomorus, and Ficus vasta have abnormal population structure with no or few individual at lower size classes and also there are species with no seedling and sapling as example Sapiumellipticum, Ficusthonningii, Ficus palmate, Syzygiumguineense, Mimusops kummel, Stereospermumkunthianu, Dichrostachyscinerea, Erythrinaabyssinica, Entadaabyssinica, and Ficus sur. Tese species need urgent conservation measures that will bring a healthy regeneration and consequently their sustainable use.

Recommendations.
To conserve the Church Forest's genetic resources and to improve the natural diversity and structure of Church forest and to provide optimal support for development of Ethiopian upper Blue Nile basin for ecological, economical, and spiritual benefts, the following general recommendations were made: (i) Complete ecological studies are vital such as, soil nutrient, soil seed bank, anthropogenic impact, and others of the forest, should be studied to identify the environmental factors responsible for the observed pattern. (ii) Analysis of IVI and species structure shows that some important tree species including Sapium ellipticum, Ficus thonningii, Ficus palmate, Syzygium guineense, Erythrina abyssinica, and Entada abyssinica are poor in regeneration and recruitment conditions, and this may be due to anthropogenic factors from the local community surrounding the area through cutting, continuous grazing, and should provide priority to the conservation of vegetation of the forest in general for its rich biodiversity area. (iv) Raising public awareness of the local community and introduction of participatory management programs should be encouraged and implemented. Tis will provide opportunity for local community to be involved in the management and conservation of the area and become benefciaries.

Data Availability
Te data sets used and/or analyzed in the study are available within the article.

Conflicts of Interest
Te authors declare that they have no conficts of interest.