The study area was located on the northern slopes of Mount Elgon (figure 1). The study area for the land use project extended from the trading centre at Kamernurgut to the Benet grasslands. Average annual temperatures decrease with altitude but do not reach freezing point in the study area. The forest zone in this area receives approximately 1500mm of precipitation annually (Synott, 1968).
Access can only be gained to Mount Elgon National Park by foot. A four day reconnaissance visit was made to the Piswa area and to a lower altitude area to determine the nature of the terrain and to gain a more detailed idea of the habitat types available for study. The lower area was rejected as a possible area of study for the vegetation, bird and mammal studies due to its confused and complex land use history. Maps (Uganda Department of Lands and Surveys map sheets 54/II, 54/III, 54/IV, 55/I and 55/III Series Y732 at 1:50,000, and the map by van Heist 1994) and local guides were used to make a preliminary identification of habitat zones according to vegetation classification, previous and present land use.
The land use survey used populated sites between the trading centre at Kamernurgut and the Benet grasslands (altitude ranged from 1200m to 2900m).
The study area for vegetation, small mammals and birds was restricted to a 6km2 area around the Piswa Patrol Hut (altitude ranged from 2800 - 2920m). Soils in the study area were Ferralsols and Nitisols and generally sandy (clay) loams (van Heist, 1994). They were neutral to slightly acidic, and were moderately deep to very deep (van Heist, 1994).
From several identified land uses and vegetation classes a variety of habitat types were selected for study. A stratified random sampling procedure was followed to select study sites from areas of each habitat type. Visits to potential sites were made with the assistance of locally born guide to confirm their land use histories. Visual information (such as burnt tree stumps, old huts, paths etc) and infomation from local people, Park Rangers and Mr. A. Katende, who had carried out research in the area in 1990, was sought to cress-check information provided by the guide.
As there are no completely undisturbed areas of forest, comparisons were conducted between presently disturbed sites and recovering sites. Recovering sites existed where National Park relocations had resulted in reduced cattle grazing activity and the abandonment of cultivation.
The vegetation in the study area comprised a mosaic of montane forest, bushland and grassland communities:
(a) Grassland: <10 cm in height; dominated by Adropogan amethystinus, Pennisetum
clandestinumand Digitaria scalarum (Graminae); grass species accounting for 15-60% species
composition; occasional shrub and herb species over 10 cm occurring with increasing frequency
towards forest edge; grazed intensively by cattle and occasionally by donkeys.
(b) Bushland: dominated by woody herbs and shrub species forming a closed layer between 1-2
m above the ground, with occasional tree saplings; tree canopy absent or below 5 % cover; Erica
trimera ssp. elgonenis (Ericaceae) abundant in shrub layer and canopy layer (where present) with
Artemesia afra (Compositae), Dichrocephella integrifolia (Compositae) and Senacio lyratus
(Compositae) particularly abundant in shrub layer; sparse understorey of forbs, pteridophytes and
grasses beneath shrub layer; sporadic grazing by cattle in grassy patches; previously cleared for
grazing and left to regenerate for six or 15-20 years.
(c) Forest: tallest trees reaching 15-25 m; 50% canopy cover with an overstorey dominated by
Afrocrania volkensii (Cornaceae), sometimes forming an association with Podocarpus milanjianus
(Podocarpaceae), and no tree understorey; Dicliptera laxata (Acanthaceae) and Impatiens
meruensis (Balsaminaceae) particularly abundant in the field layer, with Mimulopsis alpina
(Acanthaceae) more abundant in less grazed plots (where its growth form became increasingly
shrubby forming a closed layer in patches (< 40 % cover)), and with occasional shrubs occurring in
this layer; grazed intensively until either 1983 or 1990 when the human populations in the area were
evicted and grazed by cattle with varying intensity since that time.
(d) Forest edge: within 100 m of closed canopy forest and either grassland or bushland
communities; tallest trees reaching 10-15 m; <50% canopy cover; shrubs, herbs and tree saplings
forming a patchy layer (<40% cover) sharing species from each community.
(e) Formerly cultivated: abandoned for three or six years; dominated by Rumex ruwensoriensis
(Polygonaceae), Plectranthus laxiflorus (Labiatae) and Pilea tetraphylla (Urticaceae), with Urtica
massaica (Urticaceae) more common in plots where grazing by cattle was most intense; plots
near to Piswa Patrol Hut had been protected from grazing by rangers since abandonment.
Within these plant communities a variety of sites with different land use histories were selected. The mammal and bird studies were restricted to forest sites. The mammal study selected sites where human activity had previously been restricted to under canopy grazing and agriculture in clearings. The two sites selected for the bird survey were in relatively undisturbed forest on a steep slope, and in formerly grazed forest which was regenerating. The Black and White Colobus Monkey study (unpublished) was conducted in forest and grassland communities.
At each site, a Global Positioning System was used to obtain co-ordinates (the degree of accuracy is approximately to within 100m), and the altitude was recorded using an altimeter. The location of the study sites can be seen.