Effects of Land-Use Dynamics on Soil Organic Carbon and Total Nitrogen Stock, Western Ethiopia

Abstract

Soil organic carbon (SOC) and total nitrogen (TN) stock are key indicators of soil quality in tropical regions; however, their status is often degraded, especially due to massive deforestation in natural forest areas associated with extensive agricultural land use. The aim of this study was to investigate the dynamics of SOC and TN stock in different land-use systems in the Abobo woreda, Western Ethiopia. To analyze their status, 80 disturbed (composite) and 45 undisturbed soil samples were collected from the top 20 cm of soil in five major land-use types: natural forestlands, grasslands, recently developed commercial farmlands, old commercial farmlands, and small-scale cultivated lands. The results showed that SOC stock varied significantly across the different land-use types, with mean stock ranging from 32.23 Mg·ha−1 in recently developed commercial farmlands to 54.54 Mg·ha−1 in natural forestlands. The mean TN stock ranged from 2.54 Mg·ha−1 in recently developed commercial farmlands to 4.63 Mg·ha−1 in natural forestlands. With natural forestlands as a baseline and the duration ranging in age from 15 to 45 years since land-use conversion, the mean annual absolute rates of change in SOC and TN stock loss were 0.49, 1.49, 0.39, and 0.45 Mg·ha−1·yr−1 and 0.05, 0.14, 0.03, and 0.04 Mg·ha−1·yr−1 for grasslands, recently developed commercial farmlands, old commercial farmlands, and small-scale cultivated lands, respectively. The results of this study revealed that soil disturbance during forestland conversion to tillage enhanced the decomposition rate of organic matter in recently developed commercial farmlands. Nevertheless, after agricultural abandonment and vegetation restoration, the SOC and TN stock capacities were enriched in the old commercial farmlands. It is, therefore, important to effectively restore vegetation and implement sustainable land-use management practices.

Impact of Land Use Types on Soil Organic Carbon and Nitrogen Stocks: A Study from the Lal Bakaiya Watershed in Central Nepal

“…Similarly, suitable practices such as conservation tillage, zero tillage, terrace farming, and agroforestry practices should be practiced to improve the carbon storage capacity of cultivated land [36,59,65,66]. Tese fndings are in line with the research of Leul et al [17] on efects of land use dynamics on soil organic carbon and total nitrogen stock.…”

“…Te SOC stock reduced in signifcant amount after using fre for land preparation and conversion from natural forest to maize feld and change from maize feld to other crops or grassland in northern Tailand [15,16]. Similarly, converting natural vegetation cover to large-scale farmland resulted in signifcant loss of soil organic carbon and total nitrogen in Western Ethiopia [17]. Other studies also reported that a strong decrease of SOC and N after conversion of forest land to other land [18,19], and this has provided a way to raise concern about the long-term sustainability of those land use types in the tropics [20].…”

The impact of land use and cover changes on river flows in Wundanyi Catchment of Taita Hills, Kenya (1970–2030)

“…Studies in various parts of the world have shown that, in general, climate variability, slope gradient, and LUCC have a significant bearing on stream flow variations through interaction between urbanization, vegetation, soil and rocks upon which precipitation is being translated into surface runoff, stream flow and groundwater recharge (baseflow) in larger basins (over 100,000 ha) and medium catchments areas between 5000 and 500,000 ha [2][3][4]10]. Changes in rainfall patterns associated with climate change and storm duration during rainy seasons may have a significant impact on runoff and soil erosion in larger catchments rather than smaller ones [33,34]. Hence, surface runoff and river discharges in smaller catchment areas (of less than 100 ha) may be altered by natural vegetation or the influence of man, such as significant forest cover removal and water abstractions upstream, rather than by significant effects of climate change.…”

“…Land-cover changes due to reforestation and forest plantation have resulted in increased forest cover in Wundanyi catchment, thus, reducing surface runoff and soil erosion. Consequently, the amount of soil organic carbon that could otherwise be lost to land clearance and cultivation are retained in the catchment to increase 'green water' flows [33,34]. Therefore, increased forest cover in Wundanyi catchment will certainly have a positive impact on its micro-climate and hydrology in the long run.…”