Overview of a conceptual definition or sustainable land management policies

Inland valleys are defined as the upper reaches of river systems. These include valley bottoms and minor floodplains,their hydromorphic fringes and upland slopes and crests. These occupy 22-52 million ha of land in W. Africa and although of good agricultural potential are only marginally used. An agro-ecological characterization developed in the Cte d'Ivoire, is outlined on 4 levels: macro (1:1 000 000-1:5 000 000), reconnaissance (1:100 000-1:250 000), semi-detailed (1:25 000-1:50 000) and detailed (1:5000-10 000).

A study was conducted of about 8000 ha around Timau area
in Meru District to evaluate its land suitability for
agriculture. A semi detailed soil survey was carried out to
classify and map the different soil units. Based on the
relevant land qualities of each Soil Unit and physiography
they were seperated in 15 Soil Mapping Units for the various
Land Utilization Types with land use recommendations given.
The following land qualities were rated and used to assess the
suitability of each Soil Mapping Unit: soil water retention,

En el presente nmero de Unasylva se analiza la situacin forestal en las zonas urbanas y se estudia su aporte potencial a la elevacin de los niveles de vida de los habitantes en distintos escenarios urbanos.

This issue of Unasylva analyses the urban forestry situation and considers its potential for increasing living standards in different urban settings.

Extensive grazing is the predominant form of land use on at least a quarter of the world’s land surface, in which livestock are raised on food that comes mainly from rangelands. Extensive grazing differs from crop or forestry production, in which the produce remains in situ whilst growing. Evaluation for extensive grazing, unlike that for cropping or forestry, must take into account the production of both grazing forage, termed primary production, and the livestock that feed on this forage, termed secondary production.