Vegetation and Geomorphology in Northern Rhodesia: An Aspect of the Distribution of the Savanna of Central Africa

Cole, Monica M.

doi:10.2307/1794828

Cited by 36 publications

(19 citation statements)

References 3 publications

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“…Dense forest survives only on isolated hills and ridges. The abrupt and irregular boundary between forest and 'derived savanna' is largely artificial, enhanced by fire (Aubr~viUe, 1932, p. 247-8) although locally, soil types may determine its position (Cole, 1963;Moss and Morgan, 1977). The 'derived savanna' zone largely of anthropogenic origin, lies between closed forest (south) and Guinea savanna (north, Figure 2).…”

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

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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...

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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

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“…Finally when the dambo occurs in upland grasslands the dividing line, or transition zone between the seasonally saturated and nonsaturated grassland may be quite undistinguishable (Michelmore, 1939). Cole (1963) sees the present spatial distribution of vegetation, based on soil drainage as an indicator of temporaral changes in vegetation with the improvement in soil drainage. She concludes that: ' ... the dynamic [nature] of the vegetation, soils and geomorphology must be stressed.…”

Section: Soilsmentioning

confidence: 95%

“…Sodic soils may induce significant subsurface erosion as the deflocculated clays are already mobile, especially as deflocculation can occur where the proportion of exchangeable sodium is as little as 4% V Vegetation Dambo vegetation cover is determined by ecological factors -namely the microrelief; the level of the water table; and the stability of the soils, along with their physical and chemical properties (Perera, 1982). Cole (1963), in her study of the vegetation and geomorphology of Zambia, accepted the importance of climatic, edaphic and biotic influences upon the vegetation but focused on the geomorphology, through which the above factors operate:…”

Section: Soilsmentioning

confidence: 99%

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Dambos: a review

Boast

1990

Progress in Physical Geography: Earth and Environment

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This review mainly assesses the research presented on dambos since the collection of papers edited by Thomas and Goudie (1985) focused renewed attention on the study of these landforms. Prior to the 1985 supplement volume (Supplementband 52) of Zeitschrift für Geomorphologie studies of dambos had tended (with the exception of the work of Mackel) to be qualitative; spatially isolated descriptions of the morphology of dambo-like forms from different parts of Africa. There was, and still is, a lack of research into the processes of dambo formation and how dambo morphology and evolution vary spatially across Africa. However, recent work has focused greater attention on the geomorphological and hydrological mechanisms at work on and within dambos; as well as the consequences of dambo utilization by man. For the completeness of this review all aspects of dambo work are surveyed but greater emphasis is placed on the more recent investigations.

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“…Most of the woodlands are related to a geomorphology of old, low-relief erosion (planation) surfaces where the balance of weathering and erosion has produced relatively deep and leached soils over long periods of time. Topographically miombo is, to a lesser extent, also related to escarpments and steep inselberg slopes with poor soils (Cole 1963).…”

Section: Integrated Landscape Analyses Of Change Of Miombo Woodland Imentioning

confidence: 99%

Integrated landscape analyses of change of miombo woodland in tanzania and its implication for environment and human livelihood

Strömquist

Backéus

2009

Geografiska Annaler: Series A, Physical Geography

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. Landscapes bear witness to past and present natural and societal processes influencing the environment and human livelihoods. By analysing landscape change at different spatial scales over time the effects on the environment and human livelihoods of various external and internal driving forces of change can be studied. This paper presents such an analysis of miombo woodland surrounding the Mkata plains in central Tanzania. The rich natural landscape diversity of the study area in combination with its historical and political development makes it an ideal observation ground for this kind of study. The paper focuses on long‐term physical and biological changes, mainly based on satellite information but also on field studies and a review of documents and literature. The miombo woodlands are highly dynamic semi‐arid ecosystems found on a number of nutrient‐poor soil groups. Most of the woodlands are related to an old, low‐relief geomorphology of erosion surfaces with relatively deep and leached soils, or to a lesser extent also on escarpments and steep Inselberg slopes with poor soils. Each period in the past has cast its footprints on the landscape development and its potential for a sustainable future use. On a regional level there has been a continual decrease in forest area over time. Expansion of agriculture around planned villages, implemented during the 1970s, in some cases equals the loss of forest area (Mikumi‐Ulaya), whilst in other areas (Kitulangalo), the pre‐independence loss of woodland was small; the agricultural area was almost the same during the period 1975–1999, despite the fact that forests have been lost at an almost constant rate over the same period. Illegal logging and charcoal production are likely causes because of the proximity to the main highway running through the area. Contrasting to the general regional pattern are the conditions in a traditional village (Ihombwe), with low immigration of people and a maintained knowledge of the resource potential of the forest with regards to edible plants and animals. In this area the local community has control of the forest resources in a Forest Reserve, within which the woody vegetation has increased in spite of an expansion of agriculture on other types of village land. The mapping procedure has shown that factors such as access to transport and lack of local control have caused greater deforestation of certain areas than during the colonial period. Planned villages have furthermore continued to expand over forest areas well after their implementation, rapidly increasing the landscape fragmentation. One possible way to maintain landscape and biodiversity values is by the sustainable use of traditional resources, based on local knowledge of their management as illustrated by the little change observed in the traditionally used area.

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Vegetation and Geomorphology in Northern Rhodesia: An Aspect of the Distribution of the Savanna of Central Africa

Cited by 36 publications

References 3 publications

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

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

Dambos: a review

Integrated landscape analyses of change of miombo woodland in tanzania and its implication for environment and human livelihood

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