Bush encroachment is widely distributed in arid and semi-arid regions, and it has a serious impact on livestock production, especially in Africa where livestock is a primary source for the livelihoods of many people. In this study, methods of supervised classification and decision tree classification, and indexes of a land use change significance index (Ci) and a single land use dynamic degree, were applied to remote sensing imagery of Ethiopia for 1986-2016. The results show the dynamic characteristics of grassland bush encroachment in low altitude areas (pastures <1500 m above sea level) of Ethiopia in the 30 year period studied. The results revealed several interesting features of this phenomenon. (1) The area of bush encroachment showed an increasing trend, with a maximum of 3.74×103 km2 in 2003, which represented 68.97% of the total area, and declined slightly from 2003~2016. (2) Among classification types, the area of severe shrub grassland was the largest, accounting for 28.36-49.10% of the total area, while the area of moderate bush encroachment accounted for 9.77-16.68%, and slight bush encroachment accounted for 5.52-7.57%. (3) The expansion rate of shrubby grassland was 0.74% for the 30 year period, while the average annual expansion rate was 2.16% for the 8 years from 1995-2003. (4) Forest land and grassland were the two main land use types of shrub grassland transformation in low altitude areas and bush encroachment changed large amounts of forest land into grassland due to shrub grassland management. The results of this study provide basic data for revealing the impacts of development processes on subsequent bush encroachment and can inform better management for the sustainable development of grasslands in low altitude systems.
XING Yuanyuan, WANG Yongdong, YOU Yuan, SONG Qin, HARE Malicha Loje, JORRO Zinabu Bora, JIRMA Guyo Huka
. Dynamic Changes of the Bush Encroachment in Low Altitude Area of Ethiopia[J]. Journal of Resources and Ecology, 2018
, 9(3)
: 281
-289
.
DOI: 10.5814/j.issn.1674-764x.2018.03.008
[1] Abate, T, Angassa, A.2016. Conversion of savanna rangelands to bush dominated landscape in borana, southern ethiopia.Ecological Processes, 5(1): 6.
[2] Archer S, Scifres C, Bassham C, et al.1988. Autogenic succession in a subtropical savanna: conversion of grassland to thorn woodland. Ecological Monographs, 58(2): 111-127.
[3] Billi P, Alemu Y T, Ciampalini R.2015. Increased frequency of flash floods in Dire Dawa, Ethiopia: Change in rainfall intensity or human impact.Natural Hazards, 76(2): 1373-1394.
[4] Chai Hua, Fang Jiangping, Wen Ding, et al.2014. Effect of sampling method on the estimation of soil carbon and nitrogen storages in thicketed semiarid grasslands, Inner Mongolia.Acta Prataculturao Sinica, 23(6): 28-35. (in Chinese)
[5] Chen Shupeng,Tong Qingxi, Guo Huadong.1998. Research on the mechanism of remote sensing information. Beijing: Science Press, 84-113.(in Chinese)
[6] Coppock D. L.1993. Vegetation and pastoral dynamics in the southern Ethiopian rangelands: Implications for theory and management. Range ecology at disequilibrium: new models of natural variability and pastoral adaptation in African savannas (eds R. H. Behnke, I. Scoones and C. Kerven). Overseas Development Institute. London: International Institute for Environment and Development and Commonwealth Secretariat, 42-61.
[7] Coppock D. L.1994. The Borana plateau of southern Ethiopia: synthesis of pastoral research development and changes, 1980-90. ILCA (International Livestock Centre for Africa): Addis Ababa, Ethiopia.
[8] Dalle G, Maass BL, Isselstein J.2006. Rangeland condition and trend in the semi-arid Borana lowlands, southern Oromia, Ethiopia.African Journal of Range & Forage Science, 23(1): 49-58.
[9] Fensham R, Fairfax R, Archer S.2005. Rainfall, land use and woody vegetation cover change in semi- arid Australian savanna.Journal of Ecology, 93(3): 596-606.
[10] Haile G.2010. Land use/cover dynamics and its implications since the 1960s in the Borana rangelands of Southern Ethiopia.Livestock Research for Rural Development, 22(7): 132.
[11] Jia G., Epstein H., Walker D.2004. Controls over intra-seasonal dynamics of AVHRR NDVI for the Arctic tundra in northern Alaska.International Journal of Remote Sensing, 25(9): 1547-1564.
[12] Jurena PN, Archer S.2003. Woody plant establishment and spatial heterogeneity in grasslands.Ecology, 84, 907-919.
[13] Knapp A.K., Briggs J.M., Collins S.L.et al.2008. Shrub encroachment in North American grasslands: shifts in growth form dominance rapidly alters control of ecosystem carbon inputs.Global Change Biol, 14: 615-623.
[14] Lei Qingling.2006. Analysis of land use dynamic change and the landscape pattern in Shanxi. M.S. diss., Nan Jing: Hohai Univercity. (in Chinese)
[15] Li J, Okin G S, Alvarez L J, et al.2008. Effects of wind erosion on the spatial heterogeneity of soil nutrients in two desert grassland com-munities.Biogeochemistry, 88: 73-88.
[16] Li Liangcai, Deng Li, Cao Ying, et al.2012. Vegetation dynamic monitoring in mining area based on NDVI serial images and dimidiate pixel model.Journal of Central South University of Forestry & Technology, 32(6): 18-23. (in Chinese)
[17] Lu Chunyang, Qi Leigang, Sang Chaojie.2007. Analysis on Mathematic Model of Land-use Changes.Resource Development & Market, 23(1): 25-27. (in Chinese)
[18] Mcmanus K M, Morton D C, Masek J G,et al.2012. Satellite-based evidence for shrub and graminoid tundra expansion in northern Quebec from 1986 to 2010.Global Change Biology, 18(7): 2313-2323.
[19] Mengistu A.2006. Range management for eastern Africa: concepts and practices. Addis Ababa:Addis Ababa University Printing Press.
[20] Oba G.1998. Assessment of indigenous range management knowledge of the Borana pastoralists of Southern Ethiopia. Borana low land pastoral development program/GTZ Consultancy paper. Negelle/Borana.
[21] Odorico P. D.2012. Dryland climatology.Eos Transactions American Geophysical Union, 93(39): 377-378.
[22] Peng Haiying, Li Xiaoyan, Tong Shaoyu.2014. Advance in shrub encroachment in arid and semiarid region.Acta Prataculturae Sinica, 23(2): 312-322. (in Chinese)
[23] Peng Haiying, Li Xiaoyan, Tong Shaoyu.2014. Effects of shrub (Caragana microphallaLam.) encroachment on water redistribution and utilization in the typical steppe of Inner Mongolia.Acta Ecologica Sinica, 34(9): 2256-2265. (in Chinese)
[24] Tsegaye D, Moe S R, Vedeld P, et al.2010. Land-use/cover dynamics in Northern Afar rangelands, Ethiopia.Agriculture Ecosystems & Environment, 139(1-2): 174-180.
[25] Xiong Xiaogang, Han Xingguo.2005. Spatial heterogeneity in soil carbon and nitrogen resources, caused by Caragana microphylla, in the thicketization of semiarid grassland, Inner Mongolia.Acta Ecologica Sinica, 25(7): 1678-1683. (in Chinese)
[26] Zhang Hong, Shi Peijun, Zheng Qiuhong.2001. Research progress in relationship between shrub invasion and soil heterogeneity in a natural semi-arid grassland.Acta Phytoecologica Sinica, 25(3): 366-370. (in Chinese)
[27] Zhang Hong.2009. Research on dynamic-change of land-use and spatial pattern of urban area. M.S. diss., Harbin Institute of Technology.(in Chinese)
[28] Zhang yuanyuan.2012. The Preliminary research of Caracara shrub nabkhas in Inner Plateau. M.S. diss., Tianjin normal university. (in Chinese)
[29] Zhang Yufeng, Wang Fengling.2004. Analysis On the Structural Changes of Land Utilization in a Village.Journal of Arid Land Resource and Environment, 18(6): 90-94. (in Chinese)
