Abstract:
On Mount Guna higher land degradation particularly soil erosion problems has a
deleterious impact on soil fertility and depletion of soil organic carbon stock due to land
use types and slope gradient varation. Land use type, slope gradient and soil depth have
different impacts in soil properties and soil organic carbon stock variation either
positively or negatively. Therefore, the study was conducted to evaluate the effects of land
use and slope on soil organic carbon stock and soil properties of Mount Guna,
northwestern highland of Ethiopia. LULC map was done from 30 m x 30 m resolution
satellite imagery of 2021 which is freely downloaded from USGS Earth Explorer and the
classification process were done using Arc GIS 10.8 version. Stratified sampling
technique was employed. A total of 144 composite soil samples were collected from 0-15
cm and 15-30 cm soil depth under the major land use types across three slope gradients
with three replication by auger for selected soil physicochemical analaysis, of which 54
soil samples from developmental, 54 from buffer and the rest 36 soil sample was from core
zone. Correspondingly, 144 soil samples were collected for soil BD and soil moisture
content determination by core sampling method. For data analysis, the general linear
model procedure of SAS version 9.4 was used. The result showed that, land use types,
slope gradients, soil depth and land use type interact with slope classes had very highly
and highly significant difference on selected soil parameter and soil SOC stock within
developmental, buffer and core zones. The highest sand fraction, percentage of silt, BD
and Av. P were recorded under cropland within developmental and buffer zones.
Similarly, within the core zone, except Av.P which was higher under natural forest land,
all other listed parameters were higher on Guassa grass land, whereas the highest clay
percentage, SMC, pH, TN, CEC, OC and SOCS were recorded under the natural forest
land within each zone. In terms of slope classes, except sand and BD all other parameters
were increased with decreasing slope gradient within each zones. With regarding to soil
depth the sand fraction, Av. P, TN, CEC, OC and SOCS decreased with increasing in soil
depth, while the clay content, BD, SMC and pH were increased with increasing soil depth
within developmental, buffer and core zones. Regarding with interaction effects, the
highest clay, pH, TN, CEC, OC and SOCS were observed on the lower slope under
natural forest land, while the lowest was recorded on the upper slope classes of crop land
within developmental and buffer zone and under Guassa grass land within the core zone.
SOCS was decreased with increasing slope, meaning SOCS had a negatively relationship
with slope gradients. Generally land use type, slope gradient, soil depth and in some
extents by interaction cause variations in physicochemical properties of the soil and SOCS
storage of the study area.