|Berihu, Tesfay - Mekelle University|
|Girmay, Gebreyohannes - Mekelle University|
|Sebhatleab, Mulugeta - Mekelle University|
|Berhane, Emiru - Mekelle University|
|Zenebe, Amanuel - Mekelle University|
Submitted to: Agronomy for Sustainable Development
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/30/2016
Publication Date: 12/19/2016
Citation: Berihu, T., Girmay, G., Sebhatleab, M., Berhane, E., Zenebe, A., Sigua, G.C. 2016. Soil carbon and nitrogen losses following deforestation in Ethiopia. Agronomy for Sustainable Development. doi:10.1007/s13593-016-0408-4.
Interpretive Summary: Dry Afromontane forests of Ethiopia have faced vast exploitation and almost all these forests have been converted to agricultural lands, except for small fragments that were left in the most inaccessible areas or around churches. This particular area deserved additional assessment because of the following reasons: a) it has a better concentration of biodiversity; b) it is the largest natural reserve compared to the other few small patches found dispersed in the region; and c) it can better explain the evolution and type of threats that prevailed in the region. The overall objective of this study was to understand the effect of land use-land cover changes on soil organic carbon (SOC), total nitrogen (TN) and soil carbon (C) sequestration. Specific objectives were: a) to analyze the SOC and TN contents of soils with varying land use-land cover of the Desa’a dry Afromontane forest; and b) to come up with recommendations on sustainable forest land management and development. Our results support the hypothesis that conversion of forest to other land use may lead to massive losses in SOC, soil TN and other nutrients. Thus, the present land management is not sustainable. For low external input farming system in the study area, the changes in SOC and other parameters will have implications on productivity of the system as well as environmental degradation. The influence of land use change is more pronounced in the 0-20 centimeter (cm) depth than 20-40 cm depth indicating the effect of management more on the upper soil depth. The global effort towards finding sustainable solutions to the greenhouse effect has identified the potential of soils as a C sink. However, for an accurate and reliable large scale determination of SOC stock density depends on soil organic C density determination at local or small scale level. Furthermore, our present research demonstrated that the land use-land cover changes could directly affect the soil physical and chemical properties, especially soil organic C status. Therefore, there is a need for change in policies and strategies for sustainable land use that will integrate development with sustainable management of the environment. Improved management of soils is very essential to sustain soil quality and improve the productivity of farmlands which in turn can help to reduce deforestation and soil degradation.
Technical Abstract: Dry Afromontane forests of Ethiopia have faced vast exploitation and almost all these forests have been converted to agricultural lands. The disappearance of the forests has been most drastic during the past 100 years and has affected the functionality and stability of agroecosystem. The dynamics in landscape and land use-land cover significantly affected soil organic carbon (SOC) and total nitrogen (TN) in various soil depths of Afromontane forests in Northern Ethiopia. The SOC (1.9%) and TN (0.26%) were significantly higher for the middle landscape position than that observed for the upper and lower landscape positions. Soil organic carbon that ranged from 1.2% (in farmland) to 2.3% (in dense forest) also varied significantly (p<0.05) with land use-land cover types. Concentration of SOC was significantly (p<0.05) different among dense forest (2.3%), open forest (1.7%), grazing land (1.6%) and farmland (1.24%). Due to the effect of land use-land cover types, soil TN significantly (p<0.05) varied from 0.15% in the farmland to 0.31% in the dense forest. The SOC and TN of the top and lower layer soils were 2.0% and 1.5% and 0.20% to 0.27%, respectively. Soil organic carbon sequestrations of the middle landscape position (43.4 ton per hectare, t/ha) showed higher mean values than those obtained for the upper (38.9 t/ha) and lower (37.4 t/ha) landscape positions. The SOC sequestration for dense forest was significantly higher (48.5 t/ha) than that of grassland, open forest and farm land. The top soil sequestered higher SOC (44.9 t/ha) than the lower soil layer. Thus, the top soil layers of dense forest at the middle landscape positions stored significant amount of SOC. The upper landscape positions exhibits excessive grazing and clearing by the highlanders from Tigray and same practices holds in place for the lower landscape positions by the Afar pastoralists. Thus, Desa’a dry Afromontane forest should be protected by avoiding encroachments for livestock grazing, unrestricted tree cutting, and clearing to expand farmlands within the boundaries of the forest.