Ecological Study of the Vegetation in Choke-Koso Ber Mountain Range, Northwest Ethiopia
No Thumbnail Available
Date
2015-11
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Addis Ababa Universty
Abstract
Ecological Study of the vegetation in Choke-Koso Ber Mountain range was conducted in
Gojjam, Amhara zone, Northwest Ethiopia, to identify and describe floristic composition,
diversity, community types, community-environment relation, population structure and
regeneration status. A total of 212 sample plots, each with a size of 20 m x 20 m, were
systematically laid at 25 m altitudinal intervals along transect lines. In each plot,
geographical coordination, altitude, aspect, slope and identity of woody species were
recorded; percentage aerial cover of the species was estimated. Height and circumference
at breast height (CBH) were measured for each woody species with height 2.5 m and
CBH 7.85 cm. In five small sub-plots, herb species were recorded, percentage aerial
cover of the species was estimated, seedling and sapling of woody species were counted
and composite of soil samples were collected. Soil texture was determined using the
Boycouos hydrometric method and USDA Soil Textural Triangle. Soil pH was measured
using pH meter, while electrical conductivity and total dissolved salts of the soil samples
were measured using Conductivity/TDS/Salinity/ Resistivity Meter. Diversity and
multivariate analyses were conducted using appropriate packages in R program (Version
3.1.2).
243 plant species, belonging to 177 genera and 71 families, were recorded. Of these, 17
species (7%) were trees, 3 species (1.23%) shrub/tree, 37 species (15.23%) shrubs, 171
species (70.37%) herbs, 12 species (4.94%) climbers and 3 species (1.23%) mosses. Out
of the total identified species, flowering plants were represented by 228 species
(93.83%), non-flowering by 15 species (6.17%), dicots by 176 species (77.20%) and monocots by 52 species (22.80%). Asteraceae, Poaceae, Fabaceae and Lamiaceae were
the dominant families. Of the total species, 33 species (13.58%) were endemic plants to
Ethiopia. Agglomerative Hierarchical Cluster analysis resulted in three plant community
types of Afroalpine vegetation and five plant community types of Dry Evergreen
Afromontane vegetation. Analysis of Shannon and Weaver diversity index showed that
species richness, diversity and evenness varied among the plant communities. Diversity
and richness tended to decrease with increasing altitude, while species turnover tended to
increase with increasing altitude. In general, community types with largest number of
sample plots, diversified environment, highest altitudinal range and moderate disturbance
were found to have the highest species diversity, richness and evenness.
Soil textural classes of the study area were sandy loam, loamy sand, sandy clay loam,
clay loam and loam. The vegetation and the environmental data were subjected to direct
gradient analysis. The output of CCA revealed that the most influential environmental
variables that had effect on the distribution of species and segregation of some plant
community types in both Afroalpine and Dry Evergreen Afromontane vegetation were
Sand (%), Disturbances, Aspect and Slope.
ANOVA and Turkey’s pair-wise comparison showed significant different (P < 0.05)
between the community types with respect to mean of Altitude, Silt (%), Clay (%) and
Disturbance in both Afroalpine and Dry Evergreen Afromontane vegetation. In addition,
there was significant difference between the community types of Dry Evergreen
Afromontane vegetation with regard to mean of Sand (%), pH, EC and Total dissolved Salt (TDS). Pearson’s correlation test for environmental variables of Afroalpine showed
significant positive correlation (P < 0.05) occurred between Sand (%) and pH, Silt (%)
and Disturbance, and EC and TDS. On the contrary, significant negative correlation
occurred between Altitude and Slope, Sand (%) and Slope, Sand (%) and Silt (%), Sand
(%) and Clay (%), Silt (%) and Clay (%), and TDS and Disturbance. Similarly, the
correlation test for environmental variables of Dry Evergreen Afromontane vegetation
showed significant positive correlation between Altitude and Aspect, Slope and pH, Sand
(%) and EC, Sand (%) and TDS, and EC and TDS. In contrast, significant negative
correlation occurred between Altitude and Disturbance, Sand (%) and silt (%), Sand (%)
and Clay (%), Silt (%) and EC, Silt (%) and TDS, Clay (%) and EC, and Clay (%) and
TDS.
Structure was carried out for the Dry Evergreen Afromontane forest. In general,
woody species had high density in the lower DBH and height classes, and the density
gradually decreased with increasing DBH and height classes. The dominance of smallsized
woody individuals in the lower DBH and height classes indicated the characteristic
of a good regeneration status. Four patterns of population structure were identified:
Inverted J-shaped, Gaussian-curve, J-shaped and U-shaped. The total basal area of woody
species was 28.65 m2/ha. The six most important woody species were Maytenus
arbutifolia, Maesa lanceolata, Acacia abyssinica, Schefflera abyssinica, Prunus africana
and Pittosporum virdiflorum. These woody species represented 71.96% of the total
Important Vale Index. The remaining 28.04% was contributed by eighteen woody
species.
Description
Keywords
Ecological Analysis