Gombe Stream National Park

The typical vegetation of this region is miombo woodland. "Miombo" is a local name for Brachystegia, one of the commonest trees. It is a landscape of closely-spaced trees seldom more than 15 meters high, often with an undergrowth of tall coarse grass. These woods are adapted to a moderate rainfall, with a single, harsh 4-5-month dry season and yearly grass fires; only along river valleys can narrow strips of forest survive. However, Gombe's high mountains and its proximity to the lake attract enough rain to support a more extensive forest, especially in the north of the park. The Park's vegetation is thus a mosaic determined by altitude, drainage and fire.

In valley bottoms, groundwater supports an evergreen forest of tall trees, with a moderate or dense shrub layer. Where the canopy is broken, "vine tangles" may develop, covering shrubs and tree stumps with a dense mat of vines.

On drier valley floors and slopes grows a "dry" forest of trees that mostly lose their leaves in dry season. Below them grows a ground cover of shrubs and thorny vines. Dry forest forms a buffer zone between evergreen forest and open woodland.

On upper slopes there is open miombo woodland, with a low canopy and little undergrowth; this is especially common in the south of the Park.

The highest ridges and peaks of the rift escarpment are clothed in a moorland of grass and herbs with a few fire-resistant shrubs and trees.

On the lowest slopes and some of the dry ridges there is grassland with scattered trees. The lakeshore has little permanent vegetation because of disturbance by storms and man; some shrubs and herbs grow along the upper shore, there are reed-clumps at the mouths of streams, and mango trees grow in the bays favored by fishermen.

Although the lake has separated this part of Tanzania from West Africa for 20 million years, western plant and animal species have spread around the ends of the lake to its eastern shores. The flora and fauna thus show an interesting mix of eastern miombo and western forest components.

Miombo woodland supports few large grazing mammals, for three main reasons. Firstly, the high rainfall causes the grass to grow tall and coarse and difficult to digest. Secondly, the grass is not very nutritious because the rain washes nutrients out of the soil. Thirdly, in the dry season there is no food for grazers and also for browsing animals that eat trees and bushes, as most trees lose their leaves. Gombe is also impoverished because of its small size and isolation; if a species dies out, it cannot now be naturally replaced by immigration from outside. The Park used to have several herds of buffalo, but these are now extinct. The most common ungulates are bushbuck, a browser of woodland and thicket, and bushpig, a forest omnivore. (Mahale Mountains National Park is larger in size and correspondingly richer in large animals.)

Indeed, most of Gombe's larger mammals are forest species, and many of these are primates. They are successful because they can climb trees and gain access to nutritious foods that ground-living animals cannot reach. Blue monkeys, redtails and red colobus are largely confined to forest areas, where they can travel through the tree canopy, while vervets can meet most of their needs in woodland but may enter forest when food is scarce outside. The largest primates—chimpanzees and baboons—are equally at home on the ground or in the trees, and can expand their diet by being able to visit every kind of habitat as well as every level of the forest canopy.