FACTORS AFFECTING THE FLORISTIC DIVERSITY AND NESTEDNESS IN THE ISLETS OF LAKE BARDAWIL, NORTH SINAI, EGYPT: IMPLICATIONS FOR CONSERVATION العوامل المؤثرة على التنوع والتوزيع المتداخل للفلورة الموجودة على الجزر الصغيرة في بحيرة البردويل بشمال سيناء: نتائج للحماية

Document Type : Original Article

Abstract

ABSTRACT:




                The aim of this study is to investigate the ecological mechanisms related to the observed pattern of floristic diversity and nestedness in the LakeBardawil islets on the Mediterranean coast of Sinai Peninsula before the execution of the North Sinai Agricultural Development Project (NSADP) that will threaten the ecosystem of the lake. Plant species on 15 islets were identified and categorized into ecological groups related to their life-form, salt tolerance and succulence. Richness of total plant species and their ecological groups were positively correlated with islet area, number of habitats and elevation, and negatively with disturbance index. The temperature calculator detected highly significant nestedness for the entire flora and all ecological groups. Distance from the mainland had no effect on either species richness or nested pattern of total plant species and their ecological groups.
                Both the analyses of species richness and nested distribution yielded evidence for a positive species–area relationship. Although nestedness was detected for the entire plant species and their ecological groups, many species and islets exhibited idiosyncratic distribution. Idiosyncrasies could be mainly attributed to demographic stochasticity which is an important character for species interaction and diversity maintenance in arid regions. Therefore, in developing conservation strategies for the LakeBardawil islets, it is important to incorporate spatial and temporal stability of populations.




أجريت هذه الدراسة لتحديد العوامل البيئية المؤثرة على التنوع والتوزيع المتداخل للفلورة الموجودة على الجزر الصغيرة ببحيرة البردويل بشبه جزيرة سيناء قبل تشغيل المشروع الزراعي التنموي بشمال سيناء، والذي سيهدد النظام البيئي للبحيرة. وقد تم رصد الأنواع النباتية الموجودة على 15 جزيرة صغيرة، ومن ثم تقسيمها إلى مجموعات بيئية تبعاً للطرز الحياتية، وتحمل الملوحة، وقوامها العصيري.
وقد أظهرت النتائج وجود علاقة طردية بين تنوع الأنواع وکذلک مجموعاتها البيئية مع کلاً من مساحة الجزر، وعدد المواطن البيئية، والارتفاع عن سطح البحر. وقد أظهر حاسب الحرارة للتداخل وجود توزيع متداخل کلي للأنواع النباتية ومجموعاتها البيئية. وبينت نتائج الدراسة عدم تأثر تنوع الأنواع أو توزيعاتها المتداخلة على الجزر بالمسافة من البر الرئيسي.
ولقد دلل کلاً من تحليل تنوع الأنواع والتوزيع المتداخل على وجود علاقة موجبة بين الأنواع والمساحة. وعلى الرغم من وجود توزيع متداخل کلي للأنواع النباتية ومجموعاتها البيئية؛ فقد وجد عدد کبير من الأنواع والجزر ذات توزيع تمييزي، ويرجع ذلک التوزيع إلى الديموغرافية العشوائية، والتي تعتبر خاصية مميزة للتفاعل بين الأنواع والمحافظة على التنوع في المناطق الجافة. ومن خلال نتائج هذه الدراسة يتضح أهمية وضع استراتيجية للمحافظة على التنوع النباتي لجزر بحيرة البردويل، من خلال رصد التغيرات المکانية والزمنية للمجتمعات النباتية.      

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