3.1. Plant Biodiversity Dynamics
Based on the above procedural methodologies the total plant species diversity of the study area had been identified. Since, from the total plant biodiversity of the catchment 111 number of plant species was existed starting from the previous time but currently, this number has been increased to 127 with the loss of two species. This implies that the number of plant species diversity is increased by eighteen newly introduced. The percentage proportions of each species category have been presented in table 2 and table 3 for the past and current respectively.
Table 2. Category of plant species available in the past
Category of species
|
Number of abundances
|
Percentage
|
Cultivated Crop
|
11
|
9.9
|
Fruit and Vegetables
|
10
|
9.0
|
Cultivated Tree, Shrub and Herb
|
7
|
6.3
|
Grass
|
18
|
16.2
|
Wild or semi-wild Tree and shrub
|
28
|
25.2
|
Other (weed, wild herb, bush…)
|
37
|
33.3
|
Total
|
111
|
100
|
Previously, the plant species under weed, wild herb and bush categories was dominated. It indicated that it could available under all over the catchment. In contrast cultivation tree, shrub and herb are the lowest proportion from the total biodiversity.
Table 3. Category of currently available plant species
Category of species
|
Number of abundances
|
Percentage
|
Cultivated Crop
|
10
|
7.9
|
Fruit and Vegetables
|
14
|
11.0
|
Cultivated Tree, Shrub and Herb
|
17
|
13.4
|
Grass
|
21
|
16.5
|
Wild or semi-wild Tree and shrub
|
27
|
21.3
|
Other (weed, wild herb, bush…)
|
38
|
29.9
|
Total
|
127
|
100
|
The proportion of abundance that categorized under cultivated crops, wild or semi-wild trees and shrubs and others (weed, wild herb, and bush) has been decreased. It’s reduced by 25.31%, 18.31%, and 11.37% respectively (Figure 3). As the key informant indicates that most locally destroyed due to their low productive potential and the indigenous wild trees and shrubs also changed by the exotic tree and shrubs (e.g. Strawberry/ Enjori and Tree heath /Asta was the earliest bush plants), whereas different acacia tree species and valuable fruit trees and grass species were currently introduced.
In contrast, cultivated trees, shrub and herb, fruit and vegetables and grass species relative proportion have been increased by 52.98%, 18.18%, and 1.8% respectively (Figure 2). It is expected that under watershed development activity introduced plant species have been increased and the local species also regenerated. It is agreed with different biodiversity dynamics and watershed development impact studies. Since, watershed development have been incorporates different biological and physical soil and water conservation activities. These various types of biological soil and water conservation measures could been improve the vegetation status of the watershed and most of the degraded part of the watershed also protected that results regenerate different types of plant diversities [1]. In addition, in order to improve the livelihood of the community, different horticultural and improved crop varieties also incorporated. On the other hand, some plant types also dis appeared from the area. It may be due to the factor of climate change and the newly introduced plant type succession system may be affected them. This is in line with different research reports. Such as integrated watershed management bearings ecosystem balance and climate change regulation. It also contribute a significant role to natural resource conservation that results to biodiversity and ecosystem improvement[2].
Table 4. Level of species abundance during the past time
Level of abundance
|
Total frequency
|
Percentage
|
Absent
|
18
|
14
|
Low
|
45
|
34.9
|
Medium
|
53
|
41.1
|
High
|
13
|
10.1
|
Total
|
129
|
100.0
|
Table 5. Level of Species abundance during the current time
Level of abundance
|
Total frequency
|
Percentage
|
Absent
|
2
|
1.55
|
Low
|
43
|
33.33
|
Medium
|
48
|
37.21
|
High
|
36
|
27.91
|
Total
|
129
|
100
|
One of the effectiveness of watershed management intervention is improving plantation tree and vegetation diversification[3]. A number of wild food (wild edible plants) are found to be threatened where agricultural expansion and overgrazing are contributing to major threats[4]. The plant diversity and determinant factors in central Ethiopia study indicated that the number of tree and shrub species increased with the increased household location. In addition, land use type and household wealth status significantly influenced tree and shrub species richness. It also influenced by the farm size of the household which it could positively affected by the area of farm size.
The dominance of exotic tree species in farming landscapes may replace the native tree species in the long term [5]. In order to correlate with the land use land cover change, its trend is positively correlated with wild and semi-wild plant and grass species with shrub and grassland classes. The reduction and fragmentation of shrub land and natural grassland led to the decline of wild plants[6]. The watershed interventions increased the vegetative index or greenery, reduced runoff, soil loss, and land degradations and improved the bio-diversity in fragile ecosystems[7].
Long-term natural resource conservation measures positively affects the ecosystem services of the area, which results of successful regeneration of biodiversity over the time[8]. Watershed management used to ensuring the sustainable agriculture, which results of development of ecosystem diversity. Ecosystem diversity have a significant role to the improvement of biodiversity habitat[9]; [10].
On the other hand development could been the cause to land scape changes which related to the biosphere system of the earth which results climate change and loss of biodiversity. It may the cause of the alteration of ecosystem services which out puts some unfit species may be disappeared or out of the system[11];[12]. Therefore, in this study the cause of some species may of the result of climate change and ecosystem diversity dynamics.
In other study, soil and water conservation activities with protecting the area indicated that a significant role on vegetation regeneration and improvement of plant species diversity [13]; [14]. It is more prevalent on the sustainable and long term watershed development programs. Similarly, watershed development program not only conserving the environment but also it could enhances the crop diversification and patterns which results of making alternative farming system [15].