1Walter.H.and Lieth.H.1967.Klimadiagramm Weltatlas.UEB Gustav Fischer Verlag,Jena,Paris,France.
2Walter,H.1979.Vegetation of the Earth and Ecological Systems of the Geo-biosphere.2.ed,Springer Verlag,Berlin,Germany.
3Buringh,P.1979.Introduction to the Study of Soils in Tropical and Subtropical Regions .3 ed.,PUDOC,Washington,USA.
4Floret,C.and Pontanier,R.1982.L aridite en Tunisie presaharienne.Climat,sol,vegetation et amenagement .Travaux et documents de l'ORSTOM,no.150,Paris,France.
5Cornet,A.1992.Relations entre la structre spaiale des peuplements vegetaux et le bilan hydrique des sols de quelques phytocoenoses en zone aride.In:L'aridite une contrainte an developpement.Le Floc'h,E,Grouzis,M.,Cornet,C and Bille,J.C.(eds).ORSTOM,Paris,pp.245-265.
6Medina,E.and Silva,J.F.1990.Savannas of northern South-America:a steady state regulated by water-fire interactions on a background of low nutrient availability.J.Biogeogr.17,403-413.
7Holt,J.A.and Coventry,R.J.1990.Nutrient cycling in Australian tropical savannas:a review.J.Biogeogr.17,427-432.
8Scholes,R.J.1990.The influence of soil fertility on the ecology of southern African dry savannas.J.Biogeogr.17,415-419.
9Sanchez,P.A.and Salinas,J.G.1981.Low-input technology for managing Oxisols and Ultisols in tropical America.Adv.Agron.34,280-306.
10Vita-Finzi,C.1969.The Mediterranen Valleys:Geological Changes in Historical Times.Cambridge University Press,Cambridge,UK.