Soil Biodiversity and Ecosystem Functioning


Global Litter Invertebrate Decomposition Experiment

Kakamega Forest, Kenya

Site Manager

Dr. Mike Swift
Director, Tropical Soil Biology Fertility TSBF-CIAT
ICRAF Campus
United Nations Avenue, Gigiri
PO Box 30677, Nairobi
Telephone: (+254) 2 524766/55
Fax: (+254) 2 524763

Site Description

Kakamega Forest is generally considered the eastern-most remnant of the once great equatorial rainforest that stetched from West Africa through the congo Basin and into East Africa. It is the only rainforest in Kenya. Thus, Kakamega Forest is an island of immense biodiversity that has developed along its own unique evolutionary course for thousands of years and which shows a high level of endemism. Faunally and florally, Kakamega is dominated by central African lowland species, but due to its elevation (predominantly between 1500 m and 1600 m) and proximity to the formerly contiguous Nandi Forests it also contains highland elements and is thus unique.

Throughout the forest are a series of grassy glades, ranging in size from about 1 to 50 ha, with a few larger clearings. The origins of the glades are uncertain. Some are certainly recent clearings, but others predate recent records. These may have originated from past human activity such as cattle grazing or may be the result of herbivory and movements by large mammals such as buffalo and elephants (both now extirpated from the region). The glades vary a great deal in structure, some being open grass and others having a considerable number of trees or shrubs. A number of streams and small creeks run through the reserve. The larger creeks are usually bordered by a few to tens of meters of forest on either side which divide the glades, while the smallest creeks flow through open grasslands, often forming small marshy patches.

Like many of these forest islands, Kakamega has been shrinking rapidly as human population growth and resource extraction has increased over the last century. Although Kakamega Forest is somewhat protected as a government reserve, the Luhya community who live in areas surrounding the forest still rely heavily on the forest for basic needs such as fuelwood, charcoal, timber, poles, and other building materials.

Currently this region is among densely populated rural areas in the world. The pressure on limited resources of Kakamega Forest will increase, and so the efforts to manage the forest’s resources in sustainable way will be crucial to the survival of this vulnerable ecosystem.

Site Location

The GLIDE experiment for Kenya was conducted at Kakamega Forest, which abuts the eastern side of Kakamega town in Western Province of Kenya (see link to Fig 1a). The forest is located between 0† 08_ N to 0† 22_ N and 34† 46_E to 34† 57_ E. The forest lies in Lake Victoria Basin, about 150 km west of the Great African Rift Valley, from which it is separated by highlands stretching from Cheranganis in the North to the Mau Escarpment in the South (KIFCON, 1994). To the East it borders North Nandi forest atop the Nandi Escarpment (at over 2200 m), while it borders South Nandi forest towards the South-east (Kigomo, 1987).

The forest is accessible from three main roads (see link to Fig 1b): Kaimosi-Chepsanoi or Kapsabet-Chepsonoi road; Kakamega-Kitale road; and Kakamega-Kapsabet road which also passes through the forest.

Site Area

Kakamega forest currently measures approximately 19,649 hectares. Of this, dense indigenous forest covers 11,345 ha; semi-dense indigenous forest, 2,705 ha while area under degraded indigenous cover is negligible. Forest plantations cover 832 ha, scattered trees and glades cover 1,557 ha, and cleared or cultivated area cover 2,002 ha (GOK, 1994).

Site Elevation

Range of altitude is between 1500 and 1600 m above sea level and up to 2060 m atop a few scattered forested hills such as Bunyala and Lirhanda.

Annual Rainfall

The Kakamega Forest receives an average of 2080 mm of rain per year. Rainfall is bimodal with the heaviest fall in April and May (during the "long rains"), with a slightly drier June and a second peak of rain roughly in September to November (the "short rains"). January and February are the driest months.

Annual Temperature

The temperature is fairly constant throughout the year, with mean daily minimums of about 11†C (52 F) and mean daily maximums of about 26†C (79 F).


Soils are generally Acrisols of low fertility, which are heavily leached, medium to heavy texture clay loams and clays. These soils are usually acidic with pH below 5.5 (FAO, 1989). The bedrock substrate on which the forest sits consists of basalt, phenolites, and ancient gneisses. These rock formations are overlaid by a layer of clay-loam soils.

Native Forest/Vegetation Types

Plant communities (forest flora)
No complete floristic studies have been done at Kakamega. The forest hosts over 300 tree and shrub species, many of Congolean lowland forest affinities, including a number of endemic plant species, mostly ferns and orchids. The flora of the open areas and glades has not been well studied. The glades often have small trees (Combretum molle, Psidium guajava, Maesa lanceolata, Harungana madagascariensis and Chaetacme aristata). Conspicuous flowering plants include flame lilies and Gladiolus. The forest edge is lined by dense thickets of Acanthus pubescens , a shrub with sharply spined, thistle-like leaves. Marshy patches are dominated by sedges and the grass Echinocloa pyramidalis.

Several different types of plant communities are found in Kakamega Forest. In addition to areas classified as "virgin" rain forest, there are several other classifications including: colonizing forest, disturbed forest, clearings made for pit-sawing and charcoal burning, plantation areas (usually tea), natural glades, swamps, and riverine forest.

Like rainforests elsewhere, the physical structure of Kakamega Forest is complex, consisting of multiple layers of vegetation. The trees are usually well buttressed at the base. Also like other rainforests, diversity is high. There are over 150 documented species of woody trees, shrubs and vines, and 170 species of herbs of which 60 are orchids. Nine of these orchids are endemic to Kakamega rainforest. In addition, there are 62 species of ferns. This remarkable diversity results in a forest landscape where trees are festooned with orchids, mosses, other epiphytes, and lianas (climbers, woody vines). Gaps in the forest canopy are frequent, which allows for succession and the maintenance of species diversity.

Other than the information given above, very little is known about the specifics of the community or ecosystem ecology of Kakamega Forest. In areas around the GLIDE plots from which litter bag laying was done, the most common plant species are as shown (see link to table 1).

Forest fauna
The forest is best known for its diversity of birds: 367 species have been recorded. The avifauna is a mix of lowland and highland species, but lowland elements dominate. Nine of the species that occur at Kakamega are found nowhere else in Kenya, and two of its species, Turner's Eremomela (Eremomela turneri) and Chapins' Flycatcher (Muscicapa lendu), are threatened.

Insects are abundant and some are quite spectacular, such as giant Goliath beetles (Goliathus goliathus), pink and green African flower mantids (Pseudocreobotra wahlbergi), and numerous colorful butterflies. Particularly well represented groups are ants (Formicidae), Lepidopterans, Orthopterans, and beetles. Gastropod mollusks, millipedes and spiders are also common.

Kakamega is also known for its diverse snake fauna, with over 40 species, although they can be difficult to find. Lizards are more in evidence, with various skinks (Mabouya spp.), chameleons (Chamaeleo spp.), and agamas (Agama spp.) the most common. Amphibians are represented by a number of anuran species, the most common being Bufo and Phrynobatrachus toads and Ptychadena (Rana) mascariensis frogs.

Except for the monkeys (Colobus guereza, Cercopithecus mitis, C. ascanius, and Papio anubis) and squirrels (Protozerus strangeri and Heliosciurus rufobranchium), large mammals are not much in evidence. Today only smaller antelope (primarily various duikers) and bush pig (Potamochoerus porcus) are present. Small carnivores, such as Egyptian mongooses (Herpestes ichneumon), African civets (Viverra civetta), servals (Felis serval), genets (Genetta tigrina), and palm civets (Nandinia binotata) are common; some larger carnivores, including jackals (Canis adustus), spotted hyaenas (Crocuta crocuta), and leopards (Panthera pardus) also occur there. Although rodents, insectivores, and bats are clearly present, they have been little studied at Kakamega.

Challenges and opportunities
This enormous diversity has not been fully studied. Vast numbers of invertebrates, particularly soil dwelling biota have not been identified. Likewise litter fall and decomposition experiments have not been carried out at Kakamega forest. However soil macrofauna studies done were limited to agroecosystems (Brown et al., 1996). The behavior of the majority of the megafauna is only minimally understood. Limited soil studies have been conducted with little to report on. Opportunities for scientific studies are abundant in Kakamega and are of crucial importance to the conservation of this unique ecosystem.

Principal Biome/Ecoregion

Biome is tropical rainforest.

Useful References

Brown, G.G., Moreno, A.G. and Lavelle, P. (1996). Soil macrofauna under different Agricultural Systems and native vegetation in four countries of East Africa. Biological Management of Soil Fertility in Small-Scale Farming Systems in Tropical Africa, 2nd Annual report.

Deshmukh, I. K. 1982. Diversity of understory arthropods in an indigenous forest and an exotic eucalyptus plantation in western Kenya. Kenya J. Sci. Tech. Series B Biol. Sci. 3: 3-7.

FAO. (1989). Food and Food Security. FAO forestry paper, FAO (UN), 90: 1-2.

GOK (1994). Kakamega District Development Plan, 1994-1996. Office of the Vice-President and Ministry of Planning and National Development, Nairobi, 239pp

KIFCON, (1994). Kenya Indigenous Forest Conservation Programme. Kakamega Forest: The Official Guide. Forest Dept., Nairobi.

Kigomo, B. N. 1987. Some observations on regeneration trials in the Kakamega and south Nandi natural forests, Kenya. E. Afr. Agric. Forestry J. 52: 184-195.

Kokwaro, J. O. 1988. Conservation status of the Kakamega Forest in Kenya: The easternmost relic of the equatorial rain forests of Africa. Monogr. Syst. Bot. Missouri Bot. Garden 25: 471-489

Mutangah, J. G., O. M. Mwangangi and P. K. Mwaura. 1992. Kakamega Forest Vegetation Survey. Kenya Indigenous Forest Conservation Programme, National Museums of Kenya, Nairobi, Kenya.

Rowell, T. 1982. Kakamega Forest. Swara 5: 8-9.

Tsingalia, H. M. 1990. Habitat disturbance severity and patterns of abundance in Kakamega Forest Western Kenya. Afr. J. Ecol. 28: 213-226.

Photo Gallery

Photos courtesy of Frederick Ayuke



What is GLIDE?



Study Design



2005 Meeting

2003 Meeting


Image Gallery



This webpage is funded by the Soil Science Society of America.

Please contact the GLIDE headquarters (email: if you have any comments or questions.

GLIDE was a project of the International Biodiversity Observation Year 2001-2002

This material is based upon work supported in part by the National Science Foundation under Grant No. 98 06437 Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.


Search this site powered by FreeFind


This page was last updated on February 1, 2005

Apply to CSU