Savanna and Forest in Western Nigeria

Morgan, W. B.; Moss, R. P.

doi:10.2307/1157175

Cited by 22 publications

(8 citation statements)

References 8 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This difference is related to concentration differences in the soil. The forest groves in the Guinea savanna are also reported to grow on soils with a better moisture status (Morgan & Moss 1965) and a higher exchangeable calcium content (Jones 1963) than the savanna soils. Generally, however, conclusions reached by various authors on the relationship between soil conditions and the savanna/forest boundary are contradictory (cf.…”

Section: Savannas In the Lowland Forest Zone In Africamentioning

confidence: 99%

Distribution and vegetation dynamics of humid savannas in Africa and Asia

Backéus

1992

Journal of Vegetation Science

View full text Add to dashboard Cite

Abstract. A review is presented on the literature about the distribution of savannas in humid climates in Africa and Asia and their vegetation dynamics. Sections are devoted to African lowland and montane savannas (the latter divided into southern, eastern, western and northern African), Madagascar, Indian subcontinent, SE Asia and New Guinea. It is concluded that the extension of savannas under humid climatic conditions and the relation to the distribution of forests is a function of cultivation, grazing by domestic and wild animals, present and previous climate, geomorphology and soil characteristics. Once established, savannas are often maintained by fires, both natural and man‐made. Montane savannas are generally brought about by man's clearing, cultivation and burning. Fire is a stochastic variable; it creates an ecotone sensu stricto (an environmentally stochastic stress zone) at the forest/savanna border. On the other hand, if geomorphology and soil are the determinants, the transition between forest and savanna would have the character of an ecocline (a gradient zone) with fundamentally different conditions. In humid African lowland climates forests expand into savannas if the latter are not maintained by man. Whether forests also expand in less humid climates is disputed. In montane areas forest expansion may be delayed on degraded soils and when diaspores are lacking.

show abstract

Section: Savannas In the Lowland Forest Zone In Africamentioning

confidence: 99%

Distribution and vegetation dynamics of humid savannas in Africa and Asia

Backéus

1992

Journal of Vegetation Science

View full text Add to dashboard Cite

show abstract

“…The 'derived savanna' zone largely of anthropogenic origin, lies between closed forest (south) and Guinea savanna (north, Figure 2). In spite of recent population pressure, the forest-savanna boundary may be relatively stable, at least in western Nigeria (Morgan and Moss, 1965).…”

Section: Long-range Anthropogenic Changesmentioning

confidence: 99%

A survey of anthropogenic vegetation changes in West Africa during the last century ? climatic implications

Gornitz

1985

Climatic Change

View full text Add to dashboard Cite

The extent of albedo change resulting from anthropogenic modification of the vegetation cover over the last century has been investigated in West Africa. The climatic implications of these changes are briefly discussed.West Africa spans a suite of vegetation zones ranging latitudinally northward from tropical rainforest to desert scrub, and comprises environmental problems from extremely rapid deforestation of the tropical forests in Ivory Coast or Ghana to desertification in the Sahel.Historical vegetation changes have been digitized on a 1 ~ x 1 ~ grid map based on a literature survey of government censuses, forestry and agricultural reports, supplemented by atlases, and other historical, economic and geographic sources.The principal processes of land cover modification during the last century include clearing of the natural vegetation for agriculture, grazing, logging, and degradation of marginal semi-arid to arid ecosystems by excessive grazing or cultivation. Forestry surveys for West Africa suggest clearance of around 56% of the forest zone; estimated losses for Ivory Coast, Ghana, and Liberia range between 64% and 70%. Estimates of total land conversion range between 88 million ha, from the digitized land use map (Figure 4) to 122.8 million ha, from extrapolation of forestry data (Section 3.1).The change in albedo corresponding to the land use modification is relatively small, using conservative estimates for desertification amounting to an increase of around 0.4% regionally over 100 yr and 0.5% since agriculture began. Thus 4/5 of the total albedo may have occurred within the last century, Additional assumptions regarding desertification and a lower albedo value for tropical forest compensate for each other and do not significantly alter the result of the initial calculation. The maximum zones of increased albedo are concentrated in the forest zone (4 ~ -8 ~ N) and savanna-southern sahel (10 ~ 12 ~ ) which correspond to zones of maximum agricultural and population growth. Between 13 ~ N and 17 ~ N, the albedo change is small or negative due to both less intensive land utilization and replacement of scattered vegetation on exposed sandy soil by lower albedo irrigated crops.These estimates may represent a lower limit, particularly if desertification is more extensive than initially assumed. Under an extreme assumption that the entire Sahel zone between 14~ ~ N has been desertified, the regional mean albedo could increase by as much as 4%. This represents an upper limit to likely historical anthropogenic disturbances of the land surface.Although historical climate records show three major droughts during the 20th century (1910, 1940's, 1969, possibly continuing into the 1980Nicholson, 1980a;Hare, 1983), and stream flow fluctuations which correlate well with precipitation (Faure and Gac, 1981 ;Palutikof et al., 1981), these records do not appear to indicate a regional secular decrease in precipitation as suggested by several climate models. Evidence for apparent desiccation or 'desert creep' (= 'desertificati...

show abstract

“…Edaphic conditions, which, particularly in the tropics, are known to demonstrate great variability over short distances, are bound to moderate the pattern. A boundary composed of islands and enclaves of forest and savanna, as described by Morgan & Moss (1965), would therefore seem to be highly probable in many instances.…”

mentioning

confidence: 97%

“…authority on the botany of this area, maintains that the transitional community is a local type of vegetation which is intermediate in specific character between forest and savanna. Other leading workers in the area on the other hand have said that the boundary between the two vegetation types is sharp rather than transitional (Morgan & Moss, 1965;Moss 1982). Moss (1982) for instance, argues, with evidence drawn from field observations and aerial photographs of the area, that the boundary in detail and in plan is sharp and in many areas is reduced almost to a line.…”

mentioning

confidence: 99%