الفهرس 
ClimateOnly 14 pages are availabe for public view
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Abstract
R e l a t i v e l y l i t t l e r e s e a r c h has been done on t h e e f f e c t of overgrazing on t h e s t a b i l i t y and p r o d u c t i v i t y of t h e ecosystems of t h e North African Mediterranean d e s e r t . The p r e s e n t s t u d y provides p r e l i m i n a r y assessments of t h e e f f e c t of p r o t e c t i o n and c o n t r o l l e d grazing on t h e v e g e t a t i o n composition and p r o d u c t i v i t y , and t h e r a t e of consumption of phytomass by domestic animals and t h e i r grazing hehaviour, i n an ecosystem of n o n - s a l i n e d e p r e s s i o n s , 80 km west o f Alexandria. P l o t s were fenced i n t h e study a r e a i n 1974 and 1977, and d i f f e r e n t degrees of grazing p r e s s u r e (no g r a z i n g by domestic animals,and 25 and 50% of t h e g r a z i n g p r e s s u r e f r e e l y p r a c t i c e by t h e i n h a b i t a n t s ) were a p p l i e d t o t h e v e g e t a t i o n i n t h e s e plo Changes i n t h e density,cover, freq~ency~phytornasasn d t h e phenol o g i c a l sequence of s p e c i e s were recorded and compared t o t h o s e of t h e same s p e c i e s o u t s i d e t h e fenced p l o t s . S t a t i s t i c a l tests and m u l t i v a r i a t e a n a l y s e s were c a r r i e d out t o test t h e s i g n i f i - cance of t h e s e changes. Grazing animals i n each of t h e two p l o t s with 50% grazing p r e s s u r e (fenced i n 1974 and 1977) were observed f o r 24hrs every month. The s p e c i e s and organ of t h e grazed p l a n t p a r t s were ident i f i e d , and t h e numher of b i t e s , s i z e and weight of b i t e , and grazing and r e s t i n g times were recorded. A consumption index then c a l c u l a t e d t o a s s e s s t h e r e l a t i v e p r e f e r e n c e of differen p l a n t s p e c i e s by t h e domestic animals.