Pian-Upe Wildlife Reserve - Frontier-publications.co.uk

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Pian-Upe Wildlife Reserve: biological and socio-economic survey 17 The indigenous trees and shrubs of the reserve are recorded in the FTEA from the habitats listed in Table 2.2 (many are recorded from more than one habitat). Table 2.2 Habitats of the indigenous trees and shrubs of Pian-Upe Wildlife Reserve Habitat Number % Savannah woodland 21 72 Bush/thicket 11 37 Grassland 6 21 Forest edge 6 21 Riverine 5 17 Rocky places 4 18 Forest interior 2 7 Dry scrub 1 3 Dry forest 1 3 Swamp 1 3 Within each plot, species accumulation rates indicated that sampling in a 1ha plot was sufficient, but it is unlikely that the checklist is complete as not all vegetation types were sampled, and the more abundant physiognomic types are likely to contain several plant communities. 2.4.2 Vegetation/habitat types Grassland and wooded grassland This vegetation type covers the flat plains which make up most of the reserve, and is by far the most common. Cover by woody plants, mostly compound- and broad-leaved species, is less than 20%, and usually less than 10%, and there is a dense (> 75% cover) herb layer (except immediately after fire!). The dominant tree species are Acacia seyal and Balanites aegyptica, with occasional Combretum collinum, C. molle, Harrisonia abyssinica, and Maytenus senegalensis. Typical herbs and small shrubs include Clitoria ternatea, Lannea spp. Rhus spp., and Triumfetta flavescens. The grass layer is dominated by Hyparrhenia spp, and Setaria spp., with occasional Adropogon sp. and Cymbopogon spp. The herb layer is burnt annually, but only lightly grazed in the south of the reserve. Riverine woodland This vegetation type occurs in a narrow band along the Greek River and its more permanent tributaries in the south of the reserve. There is diffuse but interlocking canopy (> 40% cover) 10-15m in height, and a dense (> 75% cover) herb layer. It is also dominated by Acacia seyal and Balanites aegyptica, with A. polycantha. Typical herbs and shrubs include Capparis tomentosa, Clitoria ternatea, Fleuggea virosa, Indigofera spp., Lantana spp., and Sida spp. The grass layer is dominated by Setaria incrassata and S. holstii, with Cymbopogon pospischili and Panicum hochstetteri and abundant Cyperus rotundus. Kopjes This habitat type is scattered throughout the south of the plains, and consists of small, steepsided outcrops of rock. Over 50% of the area is bare rock with no vegetation cover. Small trees and shrubs grow in crevices and faults, and include a few Acacia spp. and Combretum spp., with Grewia bicolor, Harrisonia abyssinica, Lannea spp., Ozoroa insignis, Pappea capensis, and Ximenia caffra. There is almost no grass layer, although Imperata cylindrica forms small monospecific stands on flat patches in drainage lines. Frontier-Uganda Wildlife Protected Areas Project January 1998 Baseline Surveys Programme Report No. 13
Pian-Upe Wildlife Reserve: biological and socio-economic survey 18 Cultivated land This habitat type lies to the south of the reserve between the Greek River and Chepsikunya, and around Seryoto, although there is some cultivated land within the reserve south-west of Namalu. Some parts have been ploughed mechanically, some have been hoed manually, and some are still uncleared grassland. Live fences of Thetvia peruviana have been planted, and there are a few Balanites aegyptica left standing, but cover by woody plants is less than 10%. There is a discontinuous layer of small shrubs, herbs, and grasses, which includes Cassia spp., Indigofera spp., Sida alba, and Solanum incanum, with Brachiaria sp., Cynodon sp., Hyparrhenia filipendula, and Panicum maximum. 2.5 Discussion Wilson (1962) describes over seventy plant communities for the region, many of which have only small differences among them, but there is not a tight or obvious correlation between them and the vegetation types described here. His work was undertaken when cattle densities in the region were much higher, and he describes in detail cycles of vegetation change induced by overgrazing in which there was insufficient fuel for regular dry season burning leading to the encroachment by woody plants, and soil erosion and compaction leading to further loss of cover in the herb layer and the development of thickets. These negative changes, along with an increase in abundance of unpalatable species, made the vegetation less productive, which, under continued high grazing pressure, further hastened the changes (Wilson, 1985; Wilson, 1962). However, as a result of insecurity, between 1957 and 1980 the cattle population of Karamoja more than halved (Cisternino, 1985), and the grassland is once again subject to annual burning. At the same time, huge amounts of woody vegetation were manually removed by impoverished people reduced to producing charcoal to make a living, and this, coupled with the reduction in grazing pressure served to inadvertently and unexpectedly reverse many of the negative vegetation changes such that Wilson himself (1985) believes his maps of the 1960s (1962 and Langdale-Brown et al., 1964) are largely out of date. 2.6 Conclusions Some 3.0% of the country’s tree and shrub species were recorded in the reserve, despite the fact that it is primarily grassland, and sampling intensities were low. Further sampling is likely to identify even more species. Most of the indigenous trees and shrubs recorded are typical of savannah woodlands and thickets. The vegetation and habitats of the reserve are of enormous conservation value as they cover a large area and are essentially undisturbed, ironically, as a result of insecurity. Even under improved security conditions, however, there are fewer land use conflicts here than in most other parts of the country, and wildlife conservation and cattle keeping at moderate densities are intrinsically quite compatible. A potential threat is agricultural conversion, such as that south of the Greek River in the part of the Sebei CWA recommended for inclusion in a new National Park. Frontier-Uganda Wildlife Protected Areas Project January 1998 Baseline Surveys Programme Report No. 13
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