Exotic and African biodiversities in fruit and vegetable agroecosystems in Senegal.

The Niayes are the main horticultural production area of Senegal. This paper describes the cultivated and spontaneous biodiversities in two agroecosystems (orchards and market gardens) and some consequences to develop an agroecological approach. Data were collected from surveys on 64 orchards around Thies and from 11 market gardens in the suburb of Dakar. In orchards, cultivated fruit trees are mainly exotic fruit species such as mango, citrus, guyava. More, vegetables (e.g., chilli pepper, cucurbits, etc.) and food crops (e.g., maize, millet, cowpeas) are cultivated as secondary crops between the rows of perennial fruit crops. Plant diversity of the orchard is enriched by the hedges around the plot. These hedges include African species chosen for specific uses. In the Niayes market gardens, the range of crop species has long been known. Vegetable crops are annual plants. They are divided into: (i) African species that are multiplied locally (e.g., onion, okra, African eggplant, peppers, hibiscus), (ii) species that are not multiplied (e.g., carrots, cabbages, turnip, Irish potato), and (iii) species that can be multiplied locally but are yearly introduced (e.g., tomato, watermelon, melon, cucumber, beans). Market gardens also include some fruit species, and are surrounded by living hedges of tree and shrub strata. Horticultural systems appeared to be composed of many exotic species, but rather few local species and few varieties. The cultivation of these species which needs irrigation could be explained by the urban market demand. On the contrary, hedges, that are not watered specifically, are mainly composed by local species resistant to drought during the 8 months dry season. The value of the crop biodiversity as part of an agroecological approach will rely more on African species. (Resume d'auteur)