COMPARISON OF WOODY SPECIES DIVERSITY AND POPULATION STRUCTURE STATUS ACROSS DIFFERENT MANAGEMENT PRACTICE IN THE GOLA NATURAL VEGETATION, EASTER HARARGHE, OROMIA OF ETHIOPIA

The research was carried out at Gola natural vegetation eastern Ethiopia, to identify and Woody species' diversity, richness, evenness, and population structural status will be documented, as well as their diversity, richness, evenness, and population structural status will be analyzed. Using systematic sampling procedures, the woody species diversity and population structure of species were examined in 73 quadrats, each measuring 20 m × 20 m for trees and 5 m × 5 m for shrubs and climbers, within three land use systems: farm land (FL), grazing land (GL), and protected area (PA). The diameter at breast height (DBH), richness, evenness, and density of woody species were all measured in the vegetation. The Shannon Weiner Diversity Index was used to examine the diversity of vegetation. A total of 52 woody species belonging to 33 genera, and there were 24 families found. in Gola natural vegetation. Fabaceae was represented by the highest number of species comprising 8 (18.18 %), 9 (25.00 %) and 8 (32%) of the total number of plant species found in PA, GL, and FL. The PA site had significantly highest population density of vegetation, followed by the GL site, while the FL site had the lowest. The total basal area of PA, GL and FL were 43.73, 31.68 and 22.62 m2/ha, respectively. PA site had significantly (P= 0.042) highest Shannon’s diversity index value with mean (3.53) than the others two land use system. This result suggests significance of anthropological disturbance like grazing and farming on woody species diversity and natural forest ecosystem appeared to be adverse dependent on the category and severity of the anthropogenic disturbances.


Introduction
The richness and evenness (relative abundance) of species among and within living creatures and ecological complexes is referred to as biological diversity (Polyakov et al., 2008). One of the most important analytical aspects of the plant community is the species (Haeussler et al., 2002). Species richness is a straightforward and straightforward metric of biological diversity (Hillebrand et al, 2018). Degradation of vegetation cover and biological diversity due to anthropogenic activities is a rising anxiety in many parts of the world (Hegde and Enters, 2000). The forest coverage in Africa's is projected to be 650 million hectares, which are 17 percent of the world's forests counting a several of world biodiversity hotspots (Carney et al., 2014). In terms of biological resources (flora and fauna), Ethiopia is recognized as one of Africa's most important countries (Asfaw and Tadesse, 2001). Degradation of forest cover is one of the most pressing issues confronting humanity nowadays (Reynolds et al., 2007). Rapid human population development, agricultural expansion, settlement, poverty, forest cutting, overgrazing, invasive species, and a lack of a strong legislative framework are all key contributors to Ethiopia's forest resource degradation (Lemenih et al., 2014). The primary barrier to total forest conservation in Ethiopia is the lack of inclusion of the local community living surrounding conservation zones into the conservation activities (Woldemariam and Teketay, 2001). The country established a variety of conservation programs, including watershed management, afforestation and reforestation, restoration, and rehabilitation projects, to lessen the damage to natural forests. These methods were developed with the goal of improving vegetation protection and improving the lifestyles of local residents Wondie, 2015). For several years, the eastern half of Ethiopia has been implementing well-known conservation measures on degraded landscapes, with area exclosure being the most common conservation strategy in this region.
Gola was recognized in 2010 as a protected area, in the east Hararghe zone, East Ethiopia. Gola contains a lot of natural vegetation and a lot of wildlife. However, because it is a freshly constituted protected area, it lacks essential vegetation ecological information. As a result, progressing a comprehensive management plan is critical for effective management and preservation of the area, and this required full baseline information on stand structure and diversity status of woody species, which is essential for long-term management and conservation of the vegetation species. The primary occupations in the Gola natural vegetation region are three types of land use systems: protected natural vegetation by exclosures for more than two decades, agricultural land, and grazing land. Threfore, the study's overall goal was to identify woody species and its diversity with population structure to examine the role of conservation strategy applied in the study area in eastern Ethiopia. A complete floristic analysis of plant species diversity and woody plant population structure was conducted in three land use types: protected natural vegetation, farm land, and grazing land GL, in order to assess the conservation influence status through a complete floristic analysis of plant species diversity and woody plant population structure to fill the current information gap in woody species of Gola natural vegetation.

Study area description
Goro Gutu District, also known as the district in the East Hararghe zone, is located in the eastern part of the country. Goro-Gutu, one of the districts in East Hararghe, is part in East Ethiopia. The district covers 531 km2, accounting for approximately 2.35 percent of the zone's total area.
Karamile, the capital, is 108 kilometers west of Harar. The agro-climatic zones of Goro-Gutu district are dega (2,000-2,657 m asl), woinadega (1,500-2,000 ms asl), and kola (1,500 m asl), which cover roughly 11, 52 and 37 percent of the district's total area, respectively. The climatic conditions are defined by the district's agro-climatic zones. Agriculture (including crop and livestock production) is the people's primary source of income and employment. In the woreda, the average land holding per household is 0.37 hectares. Mixed farming is used, with sorghum, maize, and wheat being the most prevalent crops grown. The total number of livestock is 195,578.  The natural vegetation of Gola makes up the majority of the district's vegetation cover, which was created to protect natural features. The protected area of Gola's natural vegetation is home to a variety of wildlife and serves as a valuable resource for the indigenous community's future growth.
There is shared grazing pasture (CGL) and farm land used by the local people adjacent to the protected area of Gola natural vegetation, and access to these resources is unrestricted.
Systematic sampling design was carried out to gather data on the vegetation of woody species at the study location, they are dissimilar in their vegetation distribution pattern and types. The whole area of the study site was used to create appropriate transect lines and sampling quadrats for vegetation data collection in each of the land use groups. Total of six transect lines were laid (two in each land cover type). To avoid the effect of disturbances the first and the last transects lines were laid at a distance of 50 m from the edges. Along the transect lines, a total of 68 systematically selected study quadrats (20 from PA, 28 from Arab land and 25 from CGL). At every 100 m interval, quadrats of 20mx20m (400m2) were systematically created. To collect data on shrubs and climbers, five 5mx5m (25m2) sub quadrats were employed and averaged at the four corners and center of the main quadrats.

Data collection methods
In each land cover type entire the woody species vegetation encountered in all quadrats were noted and coded with scientific and local namesWith a hypsometer and a clipper, woody vegetation with DBH >2.5 cm was measured and recorded for height and diameter at breast height (DBH) respectively in each quadrat. Individuals with a single stem that branched over breast height were classified as trees. Shrubs with many straight trunks perceptibly related at ground level or one solo trunk with attached branches under breast height were smaller than ten meters in height (Powell, 2005;Nzunda, et al. 2007). The circumference of branching trees and bushes around breast height was measured separately and averaged.

Breast Height Diameter (DBH).
A clipper was used to measure DBH at a distance of roughly 1.3 m from the ground. Circumference at breast height was measured and recorded for woody species such as trees and shrubs with DBH > 2.5 cm (DBH). Individual trees/shrubs with several stems or forks below 1.3 m in height were also evaluated (Kent and Coker, 1992). The diameter of trees and bushes branching at the breast height was measured separately and averaged.

Height.
Height is a simple parameter that can be used for direct measurement. The heights of the tree were measured using Hypsometer. Identification vegetation species was done on the study sites.
Specimens were prepared and taken to Haramaya University's herbarium for identification of species that were not identified in the field.

Analysis
Diversity has been the most often utilized criterion for evaluating a site's conservation potential and ecological significance (Magurran, 1988). The best and most extensively used diversity index is the Shannon diversity index. It takes into account both the diversity and evenness of species in a group. This measure takes species composition and evenness within a given territory or community into account. To examine the level of species diversity and evenness of species distribution, the Shannon diversity indices of diversity and evenness were applied (Kent and Coker, 1992) The following is how the Shannon diversity index was determined.
Species richness was calculated using all of the species found in each plot.

S =
Evenness or equitability is a measure of how closely the abundances of different species in a given location are identical (Krebs, 1999;Magurran, 2004). The relative abundance of the different species that make up an area's richness is measured by species evenness (measure of species balance).
The following formula is used to calculate evenness: Where E stands for evenness, H' for Shannon-Wiener diversity index, and S stands for species.
The crowdedness of woody species diameter at breast height or stamp height (DBH/DSH) is known as the basal area (BA). It's a measure of dominance and a way to see the cross-section of a forest stand, and it's calculated using the formula below (Kent and Coker, 1992): Where BA = basal area in square meters per hectare, d = breast/stump height diameter in meters, and π= 3.14 The quantity of plants of a particular species per unit area is known as density. It's linked to abundance, but it's more effective for determining a species' importance. The sum of individuals per species was determined in terms of species density per convenient area unit such as a hectare, using a small quadrat inserted many times into the vegetation communities under study (Mueller-Dombois and Ellenberg, 1974).

Density = Total Number of all Trees
Sample Size in Hectare × 100 Relative Density = × 100 The probability or chance of finding a plant species in a given sample area or quadrat is defined as the number of quadrats occupied by a given species per number thrown or, more commonly, as a percentage. Frequency was calculated using quadrats and expressed as the number of quadrats occupied by a given species per number thrown or, more often, as a percentage. It is calculated as follow.

Frequency = Number of Plots in which species occur Total number of plots × 100
Relative Frequency = Frequency of individual species Frequency of all species × 100 Relative dominance is the ratio of dominance of individual tree species per dominance of all tree species.

Relative Dominance = Basal area of individual species
Total basal area of all species × 100 The ecological value of woody species was compared using Importance Value Indices (IVI) based on three criteria (relative frequency, relative density, and relative abundance). The significance of value index (IVI) was generated for each woody species using the formula below.

IVI = + RF + RDO
The Jackard similarity index was used to determine the similarity coefficient between land cover types. The pattern of species turnover among the different community types was determined using Jaccard's similarity index. This is how it was calculated: (Chidumayo, 1997).
Where J is the Jaccard similarity coefficient, a is the number of species that are found in both samples, b is the number of species that are only found in the first site, and c is the number of species that are only found in the second site. To get a percentage similarity index, the coefficient is often multiplied by 100.
All individuals encountered in the quadrats were divided into height and diameter classes to examine the population structure of woody plants (Emiru et al., 2002).
Following data collection, data was coded and arranged for analysis. Descriptive and inferential statistics were employed to analyze the quantitative data. The proportion of structural parameters of vegetation was discussed using descriptive statistics such as mean, frequency, density, and percentage. In addition to this, inferential statistics such as one-way analysis of variance (ANOVA) was employed. ANOVA was attributed to data that generated from vegetation (species richness, evenness and Shannon-Weiner Diversity Index) to examine the differences among the three-land use type. Statistical analyses were conducted using R software program (version 3.5.1.) using vegan, lattice, permute and biodiversityR package (R Core Team, 2018) at 5% significance level.
Tables and Figures were used to present the result of descriptive and inferential statistics of the study.
Overall, PA had a larger abundance and dispersion of plant species than GL and FL. The difference in woody species composition between the three land cover categories revealed that adequate conservation techniques such as area enclosures and restoration practices had a progressive influence on vegetation maintenance. The decrease in woody species variety in grazing land, according to Kibret (2008), could be a symptom of the vegetation species' increased susceptibility to animals and/or anthropogenic interference at maturity or early stages of regeneration. This could indicate that nearby residents and/or their domestic animals collected persons in the GL and FL at an early growth stage . Similarly, Sisay et al. (2001) and Tessema et al. (2011) hypothesized that extensive grazing/browsing could result in a decrease in plant species density and diversity over time.
Fabaceae was found to be the most species-rich family, accounting for 8 (18.18%), 9 (25.00%), and 8 (32%) of the total plant species identified in PA, GL, and FL, respectively. Euphorbiaceae was found to be the second most species-rich family, accounting for 4 (16.00%) and 4 (11.11%) of the total plant species identified in FL and GL, respectively. However, Euphorbiaceae and

Frequency
Frequency is defined as the number of quadrats (expressed as a percentage) in which a specific species was discovered in the research area. The uniformity of forest composition can be seen in the smaller number of species in lower frequency classes and the higher number of species in higher frequency classes. And the higher number of species in love frequency classes and the low number of species in higher frequency classes shows heterogeneity of species. In these study woody vegetation species were clustered into four frequency classes: A ≤25; B = 26-50; C = 51 -75; D ≥75. The current study found a high percentage of woody species in lower frequency groups and a low percentage of species in higher frequency classes. This indicates that generally the study sites had heterogeneous species composition. PA had more species percent with higher frequency class (class D) which are 11.33% as compare to GL and FL that had only 5.5% and 4% of species respectively. While in lower frequency class (A) GL had species percent (58.33%) than FL (52%) and PA (50%) (Fig 2). As a result, the study confirms that each land use system has a significant degree of floristic heterogeneity.
Acacia bussei was the most frequently recorded woody plant species in both PA and GL, whereas  Shannon diversity index value of PA was significantly greater than that of FL. However, the GL had not significantly different from each other, even though GL slightly higher than FL (Table 1).
This could be the result of frequent habitat disruptions in the GL and FL as a result of daily and intensive human and livestock activity for grazing and other agricultural purposes. The inability of seedlings of woody species to establish at an early stage of growth, as well as selective defoliation and crushing by grazing animals, may be contributing to the loss of species diversity in the GL and FL (Belaynesh, 2006).
In three land use types mean evenness decreased significantly (p=0.04) from the PA site through the GL to the FL site. A low mean evenness rating in FL suggests that only a few species dominate in the community. While high evenness means in PA indicates, there are constant dispersals of the species in a given ecological community (Cavalcanti and Larrazabal, 2004).
Mean of richness of woody species decreased non significantly from the PA site through the GL to the FL land use types shows average number of species per sampling unit was also higher in the PA than in the GL and FL land use type in Gola natural vegetation (

Jaccard Coefficient of Species Similarity
The similarity in family, genus, and species composition of different sites of the three land use groups was calculated using Jaccard's coefficient of similarity. The Jaccard's similarities of woody species for PA and GL were 78% of species. Similarly, 65%, similarity values were obtained from GL and FL land use types. However, the similarities between HD and LD were found to be 52% of species. Highest similarity value was obtained for the species level between PA and GL followed by GL and FL sites, while the lowest were recorded in between PA and FL.

Basal area
The cross-sectional area of all the stems in a stand at breast height is known as the basal area (BA) This directly relational trend indicated that human intervention influences basal area of vegetation.
The most important species in the vegetative community could be those having the highest basal area. The highest proportion of mean BA at the PA was covered by Acacia seyal (4.52 m 2 /ha), followed by Euphorbia adjurana (3.79 m 2 /ha). While, Acacia bussei (3.62 m 2 /ha) and Acacia senegal (3.14 m 2 /ha) were accounted the highest proportion of the mean BA and followed by Acacia tortilis (3.46 m 2 /ha) and Acacia bussei (2.54 m 2 /ha) at GL and FL respectively. In this study, cross-sectional assessment of individual species in the basal area revealed that only a few or small woody species dominated the studied area. This also shows that species with the biggest basal area do not always have the highest density, proving that species differ in size (Ayanaw and Gemado, 2018).

Importance value index
The IVI values have aided in recognizing a species' structural relevance in community organization (Premavani et al., 2014). It's also used to compare the ecological significance of species, with a high IVI score indicating a high social structure in the community. According to Shibru and Balcha (2004), species with the greatest IVI are the dominant species in a given vegetation. The  and Jasminum abyssinicum (0.80) had a lower IVI at the CGL, attracting conservation effort based on the species' social and ecological values (Table 3).
In the FL site, Grewia schweinfurthii (24.51), Acacia senegal ( (2007) and Tefera et al. (2005) reported that local people gathered woody species with DBH>30 cm for construction and charcoal production. However, most DBH frequency (54.29 percent) was restricted between the second and third diameter classes in FL diameter patterns of woody species, indicating that there were a higher number of individuals in the middle diameter classes, but a reduction towards the lower and higher diameter classes (Fig   3).This indicates a poor reproduction capacity of the species in the community.

Height Distribution
Height class were classified in to five class in Gola natural vegetation. Unlike that of DBH class, height class distribution shows reversed J-shape pattern in GL and FL sites with gradual decrement towards the largest highest class. This result showed a progress and good regeneration status of population of woody species stability in both GL and FL land use system. However, it reveals irregular pattern in PA, which is dominated by tallest trees and shrubs. most species were attained the medium canopy layer class (5-10 and 10-15m) in PA, this reveals that the number of individuals in the middle classes was the highest, and that the number of individuals in the lower and higher height classes was the lowest. The increased quantity of large-sized individuals in the upper height class in natural vegetation suggests the presence of a good number of grown vegetation species for reproduction (Yeshitela and Bekele, 2003). This argument grips factual for PA of Gola natural vegetation. This is partially because of the absence of large-scale woody exploitation by local dweller.