Abstract:
Land Use/Land Cover (LU/LC) change is one of the major global challenges induced by
anthropogenic and natural factors. Understanding the scope of LU/LC changes, the driving forces
and consequences are crucially important for maintaining sustainable use of natural resource and
promoting sustainable agriculture. This study examined the land use/land cover changes that have
occurred, during the 1973-2017 period and its driving forces. In addition, the study explored the
effects of the LU/LC changes and landscape positions on soil physicochemical properties, and
diversity of soil invertebrate macro-fauna. Unsupervised and supervised classification techniques
were employed to get thematic information from satellite imagery (1973, 1995 and 2017).
Household survey, focus group discussion and key informant interview were also used to
determine the drivers and consequences of this land use/land cover dynamics. Analysis of top soil
samples collected from four adjacent land use/land cover types (forest land, grazing land, crop
cultivated outfields and homestead garden fields) all under lower landscape position was
conducted to determine the effects of LU/LC changes on soil physicochemical properties. Besides,
analysis of top soil samples collected from three landscape positions (upper, middle and lower)
each landscape category having three land use types: forest, grazing land and cultivated land was
conducted to determine the effects of landscape positions on soil physicochemical properties. The
soil data was analyzed using ANOVA to determine variations in soil parameters among landscape
positions and land use types and treatment means comparison was determined using the least
significant difference (LSD) at 0.05 level of significances. In order to evaluate the diversity of soil
invertebrate macro fauna (SIMF) community eight parameters were measured: Shannon-Wiener
index, Simpson diversity index, Pielou’s measure of evenness, Margalef’s diversity index, the
Number of Occurrence Index, Relative abundance, Density (individuals per square meter) of each
taxon and density of all SIMF and Bray-Curtis similarity index. SIMF data was further analysed
using ANOVA and a general linear model to determine variations and the influence of land use
types on abundance and diversity of SIMF, respectively. The results showed that agricultural land
significantly increased while area covered by forest, was diminished drastically over the past four
decades (1973-2017). Forest land was reduced from 29.51% in 1973 to 20.52% in 2017, while
agricultural land use increased from 70.49% in 1973 to 79.48% in 2017. Agricultural expansion,
regime change and social unrest, population pressure, shortage of farm land and biophysical
factors were major driving forces of the LU/LC changes. Environmental implications such as
climate change, biodiversity loss, scarcity of basic forest products; habitat alteration, decline in
quality and availability of water and crop yield reduction were consequences of the LU/LC
change. The results of soil analysis indicated that there were significant (p<0.05) differences in
soil physicochemical properties among the four LU/LC types. For most parameters evaluated, the
most favourable soil properties were observed in forest land followed by homestead garden fields,
while the least favourable soil properties were found in intensively cultivated outfields. With
regard to landscape positions, the soils with best qualities were found in the lower landscape
position. Concerning the soil invertebrate macro-fauna, 332 individuals, 10 orders, 12 families
and 15 species were identified, from the collected samples that showed significant variation
(p<0.05) among land use types except wireworm, spiders and millipedes. The forest land use had
relatively higher value of species diversity (Simpson diversity index D = 0.83, Pielou’s evenness
index J′ = 0.428, Margalef diversity index d= 2.56, and Species richness r = 15) followed by
homestead garden fields, while the lowest was recorded in the cultivated outfields that had
significantly lower species diversity (Simpson diversity index D = 0.22, Pielou’s evenness index J′
= 0.075, Margalef diversity index d= 1.06, and Species richness r = 5). Overall abundance and
diversity were lowest in the cultivated outfields and grazing land and highest in homestead garden
fields and forest land. The results suggest the need for proper land use planning that ensures
conservation of existing forest cover and additional plantation of both indigenous and exotic trees
in order to maintain the ecological balance. Moreover, proper use of physical and biological soil
conservation measures on cultivated land play a decisive role in minimizing the removal of soils
and loss of soil macro fauna diversity.