النشر العلمي

  • Height-Diameter Prediction Models for Some Utilization Natural Tree Species

Abstract— This paper is a continuation of a previous paper presented by the same group in 2012. It developed and evaluated the performance of seventeen functional models that predict total tree height from diameter at breast height of five selected utilitarian natural tree species common to savannah region of the Sudan. These include Combretum micranthum, Lannea fruticosa, Sterculia setigera, Terminalia brownii, and Terminalia laxiflora. A total of 2579 tree heights and corresponding diameters at breast heights were extracted from a working plan inventory data of a natural reserved forest in the Blue Nile state. The model goodness of fit were evaluated in terms of adjusted coefficient of determination (Ra
2), root mean squared error (RMSE), Akaike’s information criterion (AIC), homogeneity of the residuals and significance of the regression parameters. The results of the study indicated that the height-diameter relationship can best be described by non-linear models. Out of the evaluated models, at least 15 models were found to give reasonable results for each species with Ra
2 range of 0.20 – 0.87 and RMSE of 0.8 – 4.2 m. The number of free model parameters was found to have little or no significant influence on the ranking of the model performance. The best five models for each species and their ranking in terms of goodness of fit differ from species to another with each species having different combination of models. Comparison of the range of data for the five studied species suggested that representation of various diameter-height classes had significant influence on the accuracy of prediction outside the range of the fitted data. This implies that application of the selected models is only useful at local stand level or at best in similar biological and stand structure conditions.

published in Journal of Forest Products & Industries

  • Modeling Height-Diameter Relationships of Selected Economically Important Natural Forest Species

Abstract— This paper developed and evaluated the performance of twenty two functional models that predict total tree height from diameter at breast height. The models were applied to five selected economically important natural tree species common to central Sudan, namely, Acacia senegal, Acacia seyal, Anogeissus leocarpus, Balanites aegyptiaca, and Combretum hartmannianum. A total of 5774 tree heights and corresponding diameters at breast heights were extracted from a working plan inventory data of a natural reserved forest in the Blue Nile state. The model goodness of fit were evaluated in terms of adjusted coefficient of determination (Ra
2), root mean squared error (RMSE), Akaike’s information criterion (AIC), homogeneity of the residuals and significance of the regression parameters. The results of the study indicated that the height-diameter relationship can best be described by non-linear models. Out of the evaluated models, at least 15 models were found to give reasonable results for each species with Ra
2range of 0.73 – 0.89 and RMSE of 0.5 – 0.9 m. The number of individual model parameters was found to have little or no significant influence on the ranking of the model performance except for the Acacias. The best five models for each species and their ranking in terms of goodness of fit differ from species to another with each species having different combination of models. Comparison of the range of data for the five studied species suggested that representation of various diameter-height classes had significant influence on the accuracy of prediction outside the range of the fitted data. This implies that application of the selected models is only useful at local stand level or at best in similar biological and stand structure conditions.

published in Journal of Forest Products & Industries

  • تأثير العلاقات العامة في المجتمعات الحديثة

 إن مستخلص هذا البحث يُعد وصفاً للمحتوى الذي بُنيت عليه العلاقات العامة من حيث النشأة والتطور والأهمية التي تؤديها العلاقات العامة في المؤسسات العامة أو الخاصة، وقد ساعدت وسائل الإعلام ووسائل الاتصال في إبراز دور العلاقات العامة في خدمة المجتمعات المدنية الحديثة في عالم تداخلت فيه المصالح والثقافات والمعارف، كما أن العلاقات العامة أصبحت وشيجة الصلة بين المؤسسات ومنسوبيها في الداخل والخارج، فالجماهير العريضة يصعب ربطها بالمنظمة أو المؤسسة إلا عبر العلاقات العامة وتوثيق عرى الروابط لصالح زيادة الإنتاج والثبات والولاء على صلة دائمة مع تلك المؤسسة، والدول المتقدمة أولت العلاقات العامة أهمية كبرى لعلمها بضرورة دور العلاقات العامة في تقوية العلاقات الدبلوماسية والاقتصادية والسياسية مع الدول النظيرة لها. لقد استخدم الباحث في هذا البحث المنهج الوصفي التحليلي أنسب المناهج في بحوث الإعلام والذي يتعرف على المشكل بكل جوانبه وأبعاده قبل الذهاب إلى الحل الناجع للمعضل المعني والخروج برؤية مقنعة تتفق والمعايير التي نصت عليها البحوث العلمية ومفرداتها ومناهج البحث المتعارف عليها عند أصحاب الاختصاص.

published in مجلة جامعة العلوم والتقانة العلمية

  • الخطاب الدعوي في منظور الإعلام الاسلامي

من أهداف هذا البحث مراجعة الخطاب الدَّعوى المعاصر وتلمس المسببات والعلل التي حلّت به ، وتباين الرؤى بين الدُّعاة في الأساليب التي يقدّم بها خطاب الدَّعوة عبر وسائل الاتصال الحديثة بين  الإباحة  والحظر، علماًَ بأنّ الوسائل أوعيه تقبل الخير والشر،  وقد نهج الباحث في بحثه هذا المنهج الوصفي التحليلي لإظهار الإيجاب والسلب في خطابنا الدعوي وكيفية الخروج بشيءٍِ متفقٌُُ عليه في الرسالة الإعلامية الدعوية التي يسعى الدُّعاة بها لإقناع المدعوين بالإسلام كعقيدة وشرعة ومنهاجاً للحياة.وقد توصل البحث إلى العديد من النتائج الهامة و التي أدرجها الباحث في خاتمة بحثه.

published in مجلة الجزيرة للعلوم التربوية والإنسانية

  • Rainfall Erosivity, Land-Use and Land-Cover Change Analysis for Gaderif, Sudan

Abstract

The purpose of this study was to analyze the combined impacts of rainfall erosivity and change in land-use and land-cover (LULC) on land degradation in three sites located in Gadarif region (eastern Sudan). Monthly rainfall dataset (1979 to 2009) were used to compute rainfall erosivity based on the Modified Fournier Index (MFI), while satellite images from three dates were utilized to detect the LULC change by means of the Maximum Likelihood Classification algorithm. The results showed no significant increasing trend in the rainfall, and the rainfall erosion power is range from high to very high in the region. The general patterns of LULC change experienced rapid conversions in natural vegetation into mechanised agricultural land which later left as bare land. Land cover changes did not occur at equal rates during all time intervals, i.e. the   agricultural land at Gadembaylia site was decreased from 73.31% in 1989 to 57.45% in 2009. While the bare land increased gradually from 12.10%, 20.34% and 38.64% in 1972, 1989 and 2009, respectively. However, the most consistent trend of LULC change was a progressive loss of the natural vegetation cover, between 1972 and 1989; natural vegetation experienced a strong loss at an annual rate ranged from 4.91% and 3.7%. Increasing trend of rainfall erosivity in conjunction with the disappearance of natural vegetation resulted in an accelerated impact on the land degradation in study area. LULC in Gadarif Region, Sudan are undergoing dramatic challenges. Therefore, the results of this study could be beneficial to stakeholders, decision makers and national planners.

Key words: Rainfall, Land degradation, Mechanized agriculture, Natural vegetation, Gadarif, Sudan

published in International Journal Of Water Resources and Arid Enviroment

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