Vegetation Ecology and Conservation Status of Evergreen Afromontane Forest Patches in Awi Zone of Amhara Region, Northwestern Ethiopia
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Date
2017-06
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Addis Ababa Universty
Abstract
The study was undertaken with the general objective of investigating the ecology and
conservation status of and determining the vegetation type of forest patches of Awi Zone,
northwestern Ethiopia. Vegetation and environmental data were collected from 154 sampling
plots (20 m × 20 m) in the study area between December 2014 and March 2016 in dry and wet
seasons. Elevation, climate, soil and land cover raster datasets were downloaded from freely
available online data sources – DIVA-GIS, Worldclim, SoilGrids and USGS, respectively.
Species frequency, density and structure of the forest patches were analyzed using descriptive
statistical tools. Floristic diversity and evenness were computed using Shannon diversity and
Evenness indices, respectively. The similarities between forest patches, between plant
communities and the study area and other study areas were computed using Sorenson’s
similarity index. The plant community types and vegetation-environment relationships were
analysed using classification and ordination tools in R package (ver. 3.2), respectively. The
distribution of a new vegetation type for Ethiopia was modelled in MaxEnt (ver. 3.3.3k). The
temporal and spatial Land use/cover dynamics of the study area and nearby forest patches were
evaluated using various tools in ArcMap 10.2 and ENVI 5.0. The results of the study revealed
that the study area harboured 212 species (122 woody and 90 herbaceous species) belonging to
169 genera and 79 families. The Shannon diversity index and evenness values of the study area
were 3.7 and 0.8, respectively. The highest number of species were recorded in Khatasa forest,
followed by Bradi, Askunabo, Ambiki, Kidamaja and Degera forests. Twenty-three species were
endemic to the Flora area. The density, basal area and dominance of woody species in the study
area were 2172.1 stems ha-1, 41.2 m2 ha-1 and 23.1 m2 ha-1, respectively. There were no
significant variations of floristic richness and structure among the forest patches. The most dominant tree species were Albizia schimperiana, Prunus africana, A. gummifera, Apodytes
dimidiata, Croton macrostachyus and Ekebergia capensis. High floristic composition similarity
was revealed between the forest patches. The forests of the study area had close affinity to other
forests in the MAF and DAF. The hierarchical classification resulted in five plant community
types which were shaped by anthropogenic and natural factors. Furthermore, the ordination
analysis showed that eight environmental variables significantly affected floristic composition of
plant communities and their distributions. The floristic analysis and vegetation distribution
modelling revealed that the study area is part of a new vegetation type – Intermediate evergreen
Afromontane forest (IAF), which was predicted to occur in Gojam and Gondar Floristic
Regions. The Land use/cover change analysis showed that the forests of the study area have
undergone significant negative changes in the past four decades. Consequently, 82% of the
primary forest was converted into other landuse types with alarming rates of forest destruction.
As a result, forest patches and a significant number of endemic and other species are threatened.
To reverse these changes, among other measures, designing effective land use planning and
undertaking restoration activities using prioritized species is highly recommended.
Key words: Awi Zone, Guangua-Illala forest, intermediate forest, Khatasa forest, land cover,
land use, primary forest, secondary forest.
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Keywords
Awi Zone, Guangua-Illala forest, intermediate forest, Khatasa forest, Land cover, Land use, Primary forest, Secondary forest