Land Usecover Dynamics And Its Impacts On Erosion Rate Soil Quality And Soil Organic Carbon And Total Nitrogen Stock At Bururi Catchment Western Ethiopia

In order to identify and sustainably utilize the services rendered by the ecosystem, it is important to understand the process of land cover and land use change and its implications for environmental conditions and ecosystem functioning. Together with GIS, remotely sensed data enhance the capacity to assess the human effects on the environment in quantitative, qualitative and spatial terms. Thus, this study assessed the pattern of LULC dynamics and its impact on soil erosion, soil quality, and organic carbon stocks in Bururi catchment, western highlands of Ethiopia. In this study aerial photographs, Landsat imageries, digital elevation model (DEM), rainfall data, soil data, and socio-economic survey data were analyzed. These data were obtained from Ethiopian Mapping Agency (EMA), online archives USGS, and National meteorological service agency. The soil data were generated by Laboratory analysis using a standard procedure while the socio-economic data were gathered from 170 sample farm households, key informants, and natural resources management experts of the study area. The Long-term (1957-2018) LULC change analysis was conducted using ERDAS Imagine (2015) software. To verify the accuracy of image classification, Kappa coefficient, producer’s accuracy, and user’s accuracy were generated. The soil loss of the study catchment was computed by employing a GIS-based Revised Universal Soil Loss Equation (RUSLE) model. To examine the effect of LULC and topographic elevation on soil quality indicators and organic carbon stocks, principal component analysis (PCA) and multi-variate analysis of variance (MANOVA) in the general linear model (GLM) procedure of SPSS (v.24) were used. The socio-economic data collected through questionnaire survey were analyzed in SPSS (v. 24) by employing both descriptive statistics and binomial logistic regression. The qualitative data gathered through interview, FGD, and field observations were used to substantiate the quantitative analysis of the questionnaire data. The result of LULC change analysis revealed that there have been remarkable changes in the LULC between 1957 and 2018. Forest cover and grassland decreased by 6.7% and 2.8%, respectively. Agricultural, Shrub, and bare/degraded lands had shown increment by 1.3%, 1.9%, and 6.3%, respectively. Due to the effect of the observed LULC change, the mean annual soil loss recorded in 1957 was 41.04 t ha-1 yr-1 whereas in 2018 increased to 48.91 t ha-1 yr-1. On the other hand, LULC and topographic elevation were found to significantly influence the spatial distribution of soil quality indicators and organic carbon stocks. Higher SOC stocks were found under forest cover, shrub land, and grassland compared to agricultural and degraded lands. The result of binomial logistic regression revealed that out of sixteen hypothesized independent variables, twelve were found to have significant influence on farmers’ decision to implement land management practices. In general, the LULC dynamics observed in the area remarkably impacted soil erosion, soil quality indicators, and organic carbon stocks. Given the severity and magnitude of the problem following LULC dynamics, the study recommends a design of proper land use policy and sustainable management of land resources to reverse the prevailing land degradation in the study area. The designed land management options need to consider the socio-demographic, biophysical, and institutional factors in the study catchment.rnKey words: LULC, RUSLE, MANOVA, SOC

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