期刊名称：Science et changements planétaires / Sécheresse
印刷版ISSN：1147-7806
电子版ISSN：1777-5922
出版年度：2008
卷号：19
期号：3
页码：193-200
DOI：10.1684/sec.2008.0145
出版社：John Libbey Eurotext
摘要：Figures See all figures Authors Ismaïla Toko , Brice Sinsin Laboratoire d’écologie appliquée de la faculté des sciences agronomiques de l’université d’Abomey-Calavi (LEA/FSA/UAC), 01 BP 526, Cotonou, Bénin Key words: Benin, biomass, erosion, grazing, soil degradation, soil surface condition, woody species DOI : 10.1684/sec.2008.0145 Page(s) : 193-200 Published in: 2008 The phenomena of subsidence and slumpflation of soil (donga) were studied in the northern Sudanian zone in Benin. Dongas appear to be vast and abrupt depressions. Their depth varies from 0.20 to 7.50 m and their size varies from 0.5 to 3.50 hectares. Their occurrence is accelerated by vegetation degradation and vulnerability of soils to erosion due to aggression by rains, weak soil structure, underground drainage, wind, overgrazing and uncontrolled bush fires. Donga shapes are circular, rectangular, or overlapping. We distinguish microdonga, mesodonga, and megadonga. The former is less deep than the second or third which are vast and abrupt. The donga process is not related to rivers as they are found at distances of about 100 to 2, 000 meters from a river. Depending on the bedrock erosion, different kinds of dongas can be found: sandy dongas, reg dongas and hillock dongas. Concerning the plant community, on the basis of ordination we determined four vegetation types. Herbaceous biomass was higher on plateaux than in dongas. Concerning life forms, hemicryptophytes and phanerophytes are the dominant life forms on plateaux. No hemicryptophytes were found in the dongas. Afro-tropical species are the most abundant phytogeographical types in the plant communities.
