Effects of Land Degradation in the uplands on Land use Changes in the Plains: The case study of Chimala River Catchment in the Usangu plains
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Date
2002
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Publisher
Sokoine University of Agriculture
Abstract
A study was carried out in Chimala River catchment in Makete-Iringa (uplands) and
Mbarali-Mbeya (plains), Tanzania to relate land use changes occurring in the plains
to upland degradation. The objectives of this study were: (a) to establish land
use/cover inventory for the catchment; (b) to assess upland vegetation degradation;
(c) to assess upland soil erosion by gully expansion; (d) to assess catchment soil
fertility status; (e) to assess the Chimala River water flow trend; and (f) to assess the
socio-economic activities related to land degradation. Aerial photographs and
satellite images were used, interpreted and analysed using GIS ArcView/ArcINFO
and ERDAS Imagine softwares. Mean monthly water levels were compared using a
student t-Test. Soil samples were collected from four different forest-covers for
organic carbon (OC) content analyses. Total nitrogen (N) contents were estimated
using C:N ratios. A structured questionnaire and SPSS programme were used to
collect and analyse socio-economic survey data. Results showed that upland
grassland decreased by 3.6% and 45.8% for 1963-77 and 1977-2001 periods
respectively due to extending cultivation activities. On the scarp, dense and open
woodlands decreased by 56.2% and 4.6% respectively for 1963-77 while for 1977-
2001 dense woodland decreased by 100% due to firewood collection; open
woodland increased by 21.2% through regeneration. Gully erosion expanded by
206% between 1963 and 1977 because of poor land management but decreased by
69% for 1977-2001 through natural recovery and afforestation. Consequently upland
vegetation degradation and gully erosion caused soil transfer from the mountains and
deposition in the plains. About 0.4% (1977) and 0.6% (2001) of the catchment area
under irrigation were abandoned to bushland due to siltation problems. River valleyiii
soils in the plains indicated adequate OC (3.4%) due to alluvial deposition thus
attracting more agricultural activities. Low OC (0.61-1.09%) indicated low N (0.06-
0.11%) as a limiting factor for paddy rice production in upper areas of the plains. No
significant variations (P<0.05) in the stream flows of Chimala River were observed
between 1960 and 1993 as a result of upland degradation. It is therefore concluded
that upland degradation has contributed significantly to land use changes/degradation
occurring in the plains that calls for more efforts to safeguard land resources in the
uplands by concerned stakeholders
Description
Dissertation
Keywords
Land Degradation, Uplands, Plains, Chimala River, Usangu plains