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Woody species composition,structure and environmental determinants in a moist evergreen Afromontane forest,southern Ethiopia

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Journal of Forestry Research 2020年第4期31卷 1173-1186页

作者： Befkadu Mewded Mesele Negash tesfaye Awas Forest and Range Land Plants Diversity Directorate Ethiopian Biodiversity InstituteP.O.Box:30726Addis AbabaEthiopia Wondo Genet College of Forestry and Natural Resources Hawassa UniversityP.O.Box:123ShashemeneEthiopia

Ethiopian moist evergreen Afromontane forests are vital for the conservation of plant diversity,including genetic pools of Coffea arabica ***,these forests are continuously shrinking and need empirical scientific studies for their effective conservation and sustainable *** study was,therefore,conducted to assess woody species composition,diversity,endemicity,structure,plant communities,and environmental determinants in Sirso moist evergreen Afromontane forest of southern *** variables such as altitude,slope,aspect,disturbance levels,and geographical location were recorded for each main *** structure and importance value index(IVI),diversity,vegetation classification,and correlation with environmental factors were analyzed.A total of 74 woody species representing 70 genera and 34 families were *** species were *** glutinosa *** *** and Prunus africana(Hook.f.)*** species categorized as vulnerable according to the IUCN red list *** highest number of species was recorded for the Rubiaceae family(8),followed by Euphorbiaceae(6),and Asteraceae(6).Five plant communities were identified:Maesa lanceolata-Dombeya torrida,Galiniera saxifraga-Cyathea manniana,Vepris dainellii-Triumfetta tomentosa,Dracaena fragrans-Rytigynia neglecta,and Arundinaria *** distribution of these communities depends on altitude,slope,and disturbance *** guineense(Wild.)DC.,Schefflera abyssinica(*** ***.)Harms,and Galiniera saxifraga(Hochst.)Bridson were species with the highest IVI,while ***,Cordia africana Lam.,Hagenia abyssinica(Bruce)***,Bridelia micrantha(Hochst.)Baill.,and *** had the *** structure of woody species showed an inverted J-shape,a J-shape,a bell-shape,and an irregular shaped *** latter three population structure revealed signs of disturbances,and were negatively correlated with altitude and *** study sh

关键词： Endemicity Plant community Population recruitment Regeneration status

Variation in seed traits and seedling vigour of Cordia africana *** in Ethiopia

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Journal of Forestry Research 2017年第5期28卷 925-934页

作者： Abayneh Derero Genene tesfaye Zewdie Woldemariam Ethiopian Environment and Forest Research Institute

Cordia africana is a very important indigenous tree species for timber and other products and services in Ethiopia. Seed traits and seedling vigour of seeds from 12 provenances of the species were compared. Mean seed mass for each provenance was assessed for 1000 seeds in 10 replications, and seed length and width were measured for 100 seeds in four replications per provenance. Germination was assessed in a glasshouse taking 400 seeds from each provenance. Root collar diameter and height of 440 seedlings grown in a nursery for 290 days in Addis Ababa were measured. Seed length, seed width, seed mass, and shoot height and root collar diameter of seedlings showed significant differences (P < 0.001) among provenances. Correlation analysis between seed and seedling traits and environmental variables revealed significant positive correlations between seed width and germination percentage, seed width and altitude, seed width and longitude and seed length and latitude. Negative correlations were obtained between seed width and temperature, seed width and rainfall, seed mass and temperature, and germination and temperature of the seed source. As expected, differences in seed trait did not explain the variability in seedling vigour. Determining quantitative variations in seed traits and seedling vigour among provenances and the patterns along environmental gradients are essential for informing decisions on the tree improvement programme of the species.

关键词： Clinal Correlation Environmental gradient Improvement Quantitative

Combining machine learning,space-time cloud restoration and phenology for farm-level wheat yield prediction

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Artificial Intelligence in Agriculture 2021年第1期5卷 208-222页

作者： Andualem Aklilu tesfaye Daniel Osgood Berhane Gessesse Aweke Department of Remote sensing at Ethiopian Space Science and Technology Institute Addis Ababa UniversityEthiopia International Research Institute for Climate and Society Earth InstituteColumbia UniversityUnited States of America Department head of the remote sensing unit at Ethiopian Space Science and Technology Institute Addis Ababa UniversityEthiopia

Though studies showed the potential of high-resolution optical sensors for crop yield prediction,several factors have limited their wider *** main factors are obstruction of cloud,identification of phenology,demand for high computing infrastructure and the complexity of statistical *** this research,we created a novel approach by combining four ***,we implemented the cloud restoration algorithm called gapfill to restore missed Normalized Difference Vegetation Index(NDVI)values derived from Sentinel-2 sensor(S2)due to cloud ***,we created square tiles as a solution for high computing infrastructure demand due to the use of high-resolution ***,we implemented gapfill following critical crop phenology ***,observations from restored images combined with original(from cloud-free images)values and applied for winter wheat *** applied seven base machine learning as well as two groups of super learning *** study successfully applied gapfill on high-resolution image to get good quality estimates for cloudy ***,yield prediction accuracy increased due to the incorporation of restored values in the regression *** models such as Generalized Linear Regression(GLM)and Random Forest(RF)showed improved capacity compared to other base and ensemble *** two models revealed RMSE of 0.001 t/ha and 0.136 t/ha on the holdout *** twomodels also revealed consistent and better performance using scatter plot analysis across three *** approach developed is useful to predict wheat yield at field scale,which is a rarely available but vital in many developmental projects,using optical sensors.

关键词： Cloud restoration Ensemble learning Machine learning Phenology Sentinel-2 Wheat yield prediction

Estimating landscape susceptibility to soil erosion using a GIS-based approach in Northern Ethiopia

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International Soil and Water Conservation Research 2017年第3期5卷 221-230页

作者： Lulseged Tamene Zenebe Adimassu Ermias Aynekulu tesfaye Yaekob International Center for Tropical Agriculture(CIAT) Chitedze Agricultural Research StationP.O.Box 158LilongweMalawi International Water Management Institute(IWMI) PO.Box 5689Addis AbabaEthiopia Agroforestry Center UN AvenueGigiriNairobiKenya Ethiopian Institute of Agricultural Research(EIAR) P.O.Box 2003Addis AbabaEthiopia

Soil erosion is a very critical form of land degradation resulting in the loss of soil nutrients and downstream sedimentation of water storages in the highlands of *** it is technically and financially impossible to conserve all landscapes affected by erosion,identification of priority areas of intervention is *** distributed erosion models can help map landscape susceptibility to erosion and identify high erosion risk *** of erosion models with geographic information systems(GIS)enables assessing evaluate the spatial variability of soil erosion and plan implementing conservation measures at landscape *** this study,the Revised Universal Soil Loss Equation adjusted for sediment delivery ratio was used in a GIS system to assess landscape sensitivity to erosion and identify *** approach was applied in three catchments with size being 10–20 km^(2) and results were compared against quantitative and semi-quantitative *** model estimated mean soil loss rates of about 45 t ha^(−1) y^(−1) with an average variability of 30%between *** estimated soil loss rate is above the tolerable limit of 10 t ha^(−1) y^(−1).The model predicted high soil loss rates at steep slopes and shoulder positions as well as along *** results of the study demonstrate that knowledge of spatial patterns of high soil loss risk areas can help deploy site-specific conservation measures.

关键词： Revised universal soil loss equation Sediment delivery ratio Hot-spot areas Watershed Sediment deposition

Direct Shear and Unconfined Compressive Behavior of Cement-clay Mixed by Lime and Nano-materials

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Direct Shear and Unconfined Compressive Behavior of Cement-c...

作者： Henok tesfaye 绍兴文理学院

学位级别：硕士

沿海地区去的软土由于含水率大和强度低,难以满足工程对地基承载能力的要求。水泥土作为一种常用的地基处理方式,但其在仍然难以在强度和变形方面很好地满足岩土工程的要求。迫切需要新的地基处理方式。本文采用石灰和纳米氧化钛作为添... 详细信息

沿海地区去的软土由于含水率大和强度低,难以满足工程对地基承载能力的要求。水泥土作为一种常用的地基处理方式,但其在仍然难以在强度和变形方面很好地满足岩土工程的要求。迫切需要新的地基处理方式。本文采用石灰和纳米氧化钛作为添加材料对传统是泥土进行改性。试样分为水泥土(SC)、石灰改性水泥土(SCL)、石灰和纳米二氧化钛复合改性水泥土(SCLT)等三类。考虑了7天、14天、28天共3个养护龄期。采用直剪试验和无侧限试验两种试验方法。实验结果表明,石灰和纳米氧化钛能够很好地对水泥土的力学性能进行改良。试样的抗压强度和剪切强度均随着养护龄期的增长而增加。石灰和纳米材料是沿海地区改性水泥土的一个有效方式

关键词：水泥土纳米材料无侧限抗压强度剪切强度

Preservation of nucleic acids by freeze-drying for next generation sequencing analyses of soil microbial communities

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Journal of Plant Ecology 2017年第1期10卷 81-90页

作者： Christina Weißbecker François Buscot tesfaye Wubet Department of Soil Ecology UFZ—Helmholtz Centre for Environmental ResearchTheodor-Lieser-Straße 406120 Halle(Saale)Germany Institute of Biology University of LeipzigJohannis-Allee 3-504103 LeipzigGermany German Centre for Integrative Biodiversity Research(iDiv)Jena-Halle-Leipzig Deutscher Platz 5e04103 LeipzigGermany

Aims Soil sample preservation is a challenging aspect in molecular studies on soil microbial *** demands for specialized sample storage equipment,chemicals and standardized protocols for nucleic acid extraction often require sample processing in a home laboratory that can be continents apart from sampling *** sampling procedures,especially when dealing with RNA,comprise immediate snap freezing of soils in liquid nitrogen and storage at−80℃until further *** these instances,organizing a reliable cooling chain to transport hundreds of soil samples between continents is very costly,if possible at *** this study we tested the effect of soil sample preservation by freeze-drying with subsequent short-term storage at 4℃or ambient temperatures compared to−80℃freezing by comparative barcoding analyses of soil microbial *** Two grassland soil samples were collected in Central Germany in the Biodiversity Exploratory Hainich-Dü*** were freeze-dried or stored at−80℃as ***-dried samples were stored at 4℃or ambient *** storage times for both storage temperatures were 1 and 7 *** DNA and RNA were extracted and bacterial and arbuscular mycorrhizal(AM)fungal communities were analyzed by amplicon 454 pyrosequencing of the 16S(V4-V5 variable region)and 18S(NS31-AM1 fragment)of ribosomal RNA(rRNA)marker genes,*** Findings Bacterial communities were sufficiently well preserved at the rDNA and rRNA level although storage effects showed as slightly decreased alpha diversity indices for the prolonged storage of freeze-dried samples for 7 *** fungal communities could be studied without significant changes at the rDNA and rRNA *** results suggest that proper sampling design followed by immediate freeze-drying of soil samples enables short-term transportation of soil samples across continents.

关键词： lyophilization soil preservation biodiversity microbial communities

Species composition, stand structure, and regeneration status of tree species in dry Afromontane forests of Awi Zone, northwestern Ethiopia

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Ecosystem Health and Sustainability 2019年第1期5卷 199-215,I0020页

作者： Getaneh Gebeyehu Teshome Soromessa tesfaye Bekele Demel Teketay Center for Environmental Science in Addis Ababa University Addis AbabaEthiopia Ethiopian Environment and Forestry Research Institute Addis AbabaEthiopia Department of Crop Science Botswana University of Agriculture and Natural ResourcesGaboroneBotswana

Species composition,structure,and regeneration status of trees were assessed in five dry Afromontane *** each of the forests,trees having≥5 cm diameter at breast height were identified and measured in 80 quadrats(20×20m^(2)).We compared tree species composition and similarities,stem densities,frequencies,basal area and importance value index of *** index was calculated to 13.3%in the least disturbed and 22.5%in highly disturbed forests.A total of 1,655 individuals representing 38 species and 28 families were *** tree densities varied from 364.1 to 664.1stem ha^(−1) with an average basal area of 20.7m^(2) ha^(−1).The analysis showed significant differences in basal areas of tree species between the least and highly disturbed *** densities ranged from 2000 to 8162.5 stem ha^(−1) and sapling densities ranged from 512.5 to 2562.5 stem ha^(−1).The anthropogenic disturbances revealed high degradation of population structure and regeneration statutes of the trees in the studied forest *** conclusion,the study provided empirical results on the dominance,population structure,importance value and regeneration status of tree species,which would be instrumental for the development of successful rehabilitation strategies for the studied forests.

关键词： Basal area disturbances importance value index regeneration specie composition similarity topographic factors

Computational method for singularly perturbed delay differential equations of the reaction-diffusion type with negative shift

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Journal of Ocean Engineering and Science 2021年第3期6卷 285-291页

作者： Gashu Gadisa Kiltu Gemechis File Duressa tesfaye Aga Bullo Department of Mathematics Madda Walabu UniversityP.O.Box 247Bale RobeEthiopia Department of Mathematics Jimma UniversityP.O.Box 378JimmaEthiopia

A numerical method for solving singularly perturbed delay differential equations with a layer or oscillatory behavior for which a small shift is introduced in the reaction term is *** stability and convergence of the method have been *** demonstrate the efficiency of the method,two model examples have been *** results obtained by the present scheme described that the finding of the present method is accurate than the findings of the previous studies.

关键词： Singularly perturbed Delay differential equations Convergence El Niño model

Assessment of Seasonal Rainfall Prediction in Ethiopia: Evaluating a Dynamic Recurrent Neural Network to Downscale ECMWF-SEAS5 Rainfall

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Advances in Atmospheric Sciences 2024年第11期41卷 2230-2244页

作者： Abebe KEBEDE Kirsten WARRACH-SAGI Thomas SCHWITALLA Volker WULFMEYER tesfaye ABEBE Markos WARE Hawassa University College of Agriculture P.O.Box 05HawassaEthiopia Institute of Physics and Meteorology University of HohenheimP.O.Box 70599StuttgartGermany Arba Minch University Water Institute of Technology Faculty of Meteorology and HydrologyP.O.Box 21Arba MinchEthiopia

Seasonal rainfall plays a vital role in both environmental dynamics and decision-making for rainfed agriculture in Ethiopia, a country often impacted by extreme climate events such as drought and flooding. Predicting the onset of the rainy season and providing localized rainfall forecasts for Ethiopia is challenging due to the changing spatiotemporal patterns and the country's rugged topography. The Climate Hazards Group Infra Red Precipitation with Station Data(CHIRPS), ERA5-Land total precipitation and temperature data are used from 1981–2022 to predict spatial rainfall by applying an artificial neural network(ANN). The recurrent neural network(RNN) is a nonlinear autoregressive network with exogenous input(NARX), which includes feed-forward connections and multiple network layers, employing the Levenberg Marquart algorithm. This method is applied to downscale data from the European Centre for Medium-range Weather Forecasts fifth-generation seasonal forecast system(ECMWF-SEAS5) and the Euro-Mediterranean Centre for Climate Change(CMCC) to the specific locations of rainfall stations in Ethiopia for the period 1980–2020. Across the stations, the results of NARX exhibit strong associations and reduced errors. The statistical results indicate that, except for the southwestern Ethiopian highlands, the downscaled monthly precipitation data exhibits high skill scores compared to the station records, demonstrating the effectiveness of the NARX approach for predicting local seasonal rainfall in Ethiopia's complex terrain. In addition to this spatial ANN of the summer season precipitation, temperature, as well as the combination of these two variables, show promising results.

关键词： station prediction downscaling artificial neural networks rainfall