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| 1 | Effect of Vachellia tortilis on understory vegetation,herbaceous biomass and soil nutrients along a grazing gradient in a semi-arid African savanna显示文摘The spatial pattern and abundance of herbaceous vegetation in semi-arid savannas are dictated by a complex and dynamic interaction between trees and grasses. Scattered trees alter the composition and spatial distribution of herbaceous vegetation under their canopies. Therefore, we studied the effect of Vachellia tortilis on herbaceous vegetation composition, biomass and basal area, and soil nutrients on sites with varying grazing intensities in the central rift valley of Ethiopia. Data were collected on species composition, cover and biomass of herbs and grasses, and soil moisture and nutrient contents under light,medium, and heavy grazing pressures, both under the inside and outside of V. tortilis canopies. Species richness was similar in both locations but decreased with increased grazing. Only the overall biomass and herb cover were significantly greater under the canopy than outside, and overall biomass showed significant unchanging decline with increased grazing. However, vegetation cover was significantly greater on moderately grazed sites compared to low and heavily grazed sites. All soil variables were significantly higher under V. tortilis canopies than outside.Our findings suggest that V. tortilis has more effect on composition and diversity of herbaceous vegetation than on species richness, and that V. tortilis promotes the herbaceous layer biomass by reducing soil moisture loss and increasing soil fertility under the inside than outside the canopies. Therefore, we suggest that management practices should be directed on reducing pressure on V. tortilis by regulating grazing. Low to moderate grazing levels(i.e., a stocking rate less than 39.6 TLU ha^(-1) yr^(-1)) seems to be tolerable to ensure sustainable conservation of the species in the study area in particular and in semi-arid savannas in general. | Temesgen Yadeta Elmar Veenendaal Karle Sykora Zewdu K.Tessema Addisu Asefa | 2018 | Journal of Forestry Research2018，29，6： | 3 |
| 2 | Perception and attitude of pastoralists on livestock-wildlife interactions around Awash National Park, Ethiopia: implication for biodiversity conservation显示文摘Introduction:Pastoral livestock share grazing areas and watering points with wildlife around the protected areas in Eastern Africa.This causes a high degree of livestock-wildlife interactions,leading to conflicts between the local community and park staff.Thus,understanding the perception and attitude of local people towards livestockwildlife interaction is very crucial to optimize both livestock production and biodiversity conservation in protected areas.This paper presents the perception and attitude of local community towards livestock-wildlife interactions around Awash National Park(ANP),Ethiopia.Methods:Interview to 180 randomly selected households,representing Afar,Ittu,and Kereyu ethnic groups living around ANP,was conducted from August to December 2015 using a semi-structured questionnaire.Data on community attitude towards wildlife,livestock production systems,and its constraints were collected through focus group-and key informant discussions.We used ordinal logistic regression model to analyze community attitude towards wildlife conservation.Results:Respondents ranked feed shortage(0.38),lack of water(0.32),and climate change(0.30)as the major constraints of livestock production around ANP.A high degree of conflict(79%;χ^(2)=24.09;df=2;P=0.000)between the local community and park was recorded.About 73%of the households would be ready to live in harmony with the park.However,85%of park staff considered the community as a threat,due to high livestock grazing pressure and illegal park resource use.Overall,community attitude towards wildlife significantly varied(χ^(2)=46.28;df=4;P=0.00)particularly due to educational level(χ^(2)=15.96;df=6;P=0.014),income source(χ^(2)=16.77;df=2;P=0.00),and distance of household from ANP(χ^(2)=20.51;df=4;P=0.00).The logistic regression model revealed that ethnic group,education,benefit obtained,and conflict with the park were significantly associated with attitude towards wildlife(χ^(2)15=76.62;df=16;P=0.000).Conclusions:Majority of respondents showed positive attitude towards wildlife,implying a better chance to mobilize the community for conservation activities in the park.Thus,expansion of formal and adult education as well as livelihood diversification strategies that could benefit the pastoral community would help to improve community attitude towards wildlife so that both wildlife conservation and livestock production can be optimized around ANP. | Yihew Biru Zewdu K.Tessema Mengistu Urge | 2017 | Ecological Processes2017，6，1： | 1 |
| 3 | Influence of Grazing on Soil Seed Banks Determines the Restoration Potential of Aboveground Vegetation in a Semi‐arid Savanna of Ethiopia显示文摘 | Zewdu K.Tessema Willem F.de Boer Robert M. T.Baars Herbert H. T.Prins | 2012 | Biotropica2012，，2： | 1 |
| 4 | Effect of exclosure ages on woody plant structure,diversity and regeneration potential in the western Tigray region of Ethiopia显示文摘Exclosure is a method of rehabilitating degraded lands by protecting them from the interference of animals and from human encroachment, and is used to regenerate native vegetation as a way to reduce soil erosion, increase rain water infiltration and provide fodder and woody biomass in degraded grazing lands. Therefore, we studied woody plant structure, diversity and regeneration potentials in 5-and 10-year grazing exclosures in comparison with open grazed sites in a semi-arid environment. Data on species diversity, abundance, structure, basal area, frequency, density, and regeneration status were collected from 270 sample plots. Forty-one woody species representing 20 families were identified, with 18, 28 and 38 species found in open grazed areas, and in 5-and 10-year grazing exclosures, respectively. The 10-year grazing exclosures had a higher(P <0.05) species richness and plant densities compared to the 5-year grazing exclosures and the open grazed areas. The population structure and regeneration status of woody species in both grazing exclosures showed an inverted J-shape, indicating a healthy regeneration status, whereas hampered regeneration was observed in open grazed areas. The establishment of grazing exclosures had positive effects in restoring woody plant diversity and improving vegetation structure and regeneration potentials of degraded grazing lands. | Tsegay Gebregerges Zewdu K.Tessema Emiru Birhane | 2018 | Journal of Forestry Research2018，29，3： | 1 |
| 5 | Rangeland water requirement satisfaction index under rainfall variability and predicting future rainfall scenarios: implication for availability of feed resources显示文摘Introduction:Rangeland ecosystems provide multiple ecosystem services,including feed resources for wild and domestic herbivores in semi-arid areas.However,under the ever increasing environmental changes,the impact of rainfall variability on the productivity and vegetation dynamics of rangelands are the great challenges that pastoral community are facing today.As a result,the potentials of most rangelands in semi-arid ecosystems affect the livestockproduction.Therefore,we studied the interconnections between the long-term rainfall variation and the rangeland Water Requirement and Satisfaction Index(WRSI)in Mieso,Jigjiga,and Shinile districts under pastoral conditions of Ethiopia.Methods:The base period rainfall data(1984–2015)was obtained from the National Meteorological Agency of Ethiopia,whereas the future rainfall trend was predicted using MarkSim software(Representative Concentration Pathways 4.5 GHG concentration trajectory).Mann-Kendall’s statistical tests,coefficient of variation,LEAP software(version 2.61),and Minitab Software(version 15)were used to assess the relationship between rangeland WRSI and long-term rainfall variability.Results:The result indicated that mean annual rainfall anomaly had strong positive correlation with rangeland WRSI in Mieso(P<0.05),Jigjiga(P<0.001),and Shinile(P<0.001)pastoral areas.Similarly,short and long rainy seasons had positive association(P<0.001)with rangeland WRSI,especially in Jigjiga and Shinile pastoral districts.The base period rainfall as well as the predicted annual rainfall showed variability in amount and distribution in all studied districts in pastoral areas of Ethiopia.Conclusions:The mean annual rainfall anomaly is correlated with the rangeland WRSI.Moreover,the future rainfall trend analysis indicated that variability of rainfall would be expected in between the years 2020–2049,2040–2069,and 2070–2099.Thus,the future rainfall variability would limit future rangeland WRSI under pastoral conditions of Ethiopia.Based on our study,we suggested establishment and implementation of early warning systems to reduce the likely impact of rainfall variability on future rangeland potential in dry lands under the pastoral production systems in eastern Ethiopia. | Hassen M.Ahmed Zewdu K.Tessema Adugna Tolera Diriba Korecha | 2017 | Ecological Processes2017，6，1： | 0 |
| 6 | Effect of Senna obtusifolia(L.)invasion on herbaceous vegetation and soil properties of rangelands in the western Tigray,northern Ethiopia显示文摘Introduction:Invasion of exotic plant species is a well-known threat to native ecosystems since it directly affects native plant communities by altering their composition and diversity.Moreover,exotic plant species displace native species through competition,changes in ecosystem processes,or allelopathic effects.Senna obtusifolia(L.)invasion has affected the growth and productivity of herbaceous vegetation in semi-arid regions of northern Ethiopia.Here,we investigated the species composition,species diversity,aboveground biomass,and basal cover of herbaceous vegetation,as well as soil properties of rangelands along three S.obtusifolia invasion levels.Methods:Herbaceous vegetation and soil properties were studied at two locations,Kafta Humera and Tsegede districts,in the western Tigray region of northern Ethiopia under three levels of S.obtusifolia invasion,i.e.,non-invaded,lightly invaded,and heavily invaded.Herbaceous plant species composition and their abundance were assessed using a 1-m^(2) quadrat during the flowering stage of most herbaceous species from mid-August to September 2015.Native species were classified into different functional groups and palatability classes,which can be useful in understanding mechanisms underlying the differential responses of native plants to invasion.The percentage of basal cover for S.obtusifolia and native species and that of bare ground were estimated in each quadrat.Similar to sampling of the herbaceous species,soil samples at a depth of 0–20 cm were taken for analyzing soil physical and chemical properties.Results:Highly palatable grasses and legumes based on the frequency of occurrence were 1.9 and 3.8 times higher in non-invaded sites than in lightly and heavily invaded sites,respectively.Furthermore,unpalatable plant species were 4.0 times higher in the heavily invaded sites than in the lightly invaded sites.Aboveground biomass,basal cover,and species diversity of the herbaceous vegetation were significantly(P<0.01)lower in the heavily invaded sites compared to the non-invaded sites.However,most soil properties were not affected by S.obtusifolia invasion compared with non-invaded sites in our study.Conclusions:Our findings contribute towards better understanding of how S.obtusifolia invasion affects the community structure and composition of native herbaceous vegetation in semi-arid rangelands in northern Ethiopia.Further long-term studies are required to understand the mechanisms of how S.obtusifolia invasion influences soil properties for better control and eradication of its invasion in the semi-arid rangelands of northern Ethiopia. | Maru G.Gebrekiros Zewdu K.Tessema | 2018 | Ecological Processes2018，7，1： | 0 |
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