Studies on distribution, composition and land use potential of selected woodland vegetation of Rukwa region, Tanzania

This study was undertaken with three main objectives: First to determine the spatial distribution of woodlands of the region. Secondly, to establish the composition, structure and environment of the selected woodland, habitats. The third objective was to examine the extent to which LANDSAT data in both pictorial and digital formats could be used as a source of information for vegetation mapping in Tanzania. The vegetation was mapped using LANDSAT-1 multisprectral scanner in agency (MSS) and aerial photographs. The satellite scenes used for this study are indicated. The normal procedures of multistage approach of vegetation sampling were followed. The initial stage of the study entailed the acquiring of the standard pre-processed LANDSAT-1 MSS imagery. The next stage was imagery farm liarisation including a background course on remote sensing techniques, with particular emphasis on vegetation mapping. The background course was then followed by a preliminary interpretation using collateral data as provided in different reports, maps and aerial photographs. From the information gained during the preliminary interpretation, an image interpretation key for the different vegetation types was developed, based mainly on tone, colourad texture; and a legend of the vegetation types was prepared. The findings include the following: (i) The Rukwa experience has revealed that forests, revering vegetation, swamps and the broader categories as highland vegetation, escarpment vegetation have an object and Ariel accuracy of 100%. That is, it is difficult to misinterpret them. (ii) The mapping accuracy for woodland is also high. The other vegetation types in the legend can be confused because their tonal signatures are not very distinct. (iii) With unsupervised classification of all frames, themes 1 and 2 consistently represented burning at high and low intensities respectively. The differential burning intensities were observed to be caused by differences in vegetation structure and the amount of fuel available for burning. (iv) On the North Rukwa frame the results were better for woodland and grassland vegetation types. The confusion is presumably because of the similarity in their reflectances. (v) Forest of Rukwa region are confined to mountain area, although not all mountains in the region are covered by forests. Miombo woodland in Rukwa Region occupies a range of relief types from the very little dissected area to the key rugged areas. On the very rugged areas there is a mixture of physiognomic vegetation types. (vi)Vegetation zones have been correlated with rainfall. In Rukwa Region miombo woodland does not grow in areas with rainfall less than 900mm. (vii) Areas with marginal soil water availability appear to support Acacia woodland, bushlands of the Rukwa valley, the grasslands and bushed grasslands of the plateau and the Kirando grasslands. (viii) Miombo woodland grows in a variety of soil types, although not in the poorly drained soils of mbugas and river valleys, in which sedges and grass grow boardered by combretum. (ix) The most widely distributed Brachystegia species was Brachystegiaspeciformis suggesting broad adaptability to a variety of conditions within the “miombo climate”. (x) Rocky and step escarpments with shallow and compact soils e.g. Mwazya Hills and some parts of Lake Tanganyika Escarpments were mainly dominated by Brachystegiabussei and Brachystegiaallenii. (xi) The excessively drained sandy soils e.g around Namanyere area, support grasslands with scattered trees and bushes of Acacia Albida. The thesis concludes that it can generally be stated that multiple usage of land without proper management practices especially in the plateau, where the combination of livestock grazing, fire and lumbering and shifting cultivation has left many parts devoid of their original vegetation. There are indications that the forests of Rukwa Region used to extend well beyond their existing boundaries. Their dissapearance in many areas probably have been largely affected by human influence.