Miombo Ecoregion Vision Report - Biodiversity Foundation for Africa

Miombo Ecoregion Report, page 20
Edaphic grasslands, floodplains, dambos and wetlands are, however, included within the revised
ecoregion. They are considered to be an integral part of the woodland landscape and ecological
processes, and functionally are not separable.
Table 1. Revised Miombo Ecoregion vegetation units. 2
Vegetation unit WWF (1999) unit area (km 2 )
Itigi thicket 48 15,405
Cryptosepalum dry forest 32 37,908
Wet miombo woodland 49 (most), 50 1,358,175
Dry miombo woodland 52, 53 1,214,533
Burkea–Terminalia woodland 57 (part) 96,162
Mopane woodland 54 (part), 55 (part) 384,037
Baikiaea woodland 51, 58 (part) 260,171
Acacia–Combretum woodland 54 (part) 103,887
Wetland grasslands 56 (part), 63 179,290
Other areas (not part of ecoregion), e.g. water
bodies, mountains
167,636
TOTAL 3,817,204
3.2 Vegetation Types
The two characteristic features of the Southern Caesalpinoid Woodland Ecoregion are the
presence of woodland dominated by trees from the legume subfamily Caesalpinioideae, such as
Brachystegia, Julbernardia, Isoberlinia, Baikiaea, Cryptosepalum, Colophospermum and
Burkea, and the presence of a well-developed grass layer composed of C4 grasses. Caesalpinoid
woodlands are composed of pinnate broad-leaved tree species, most being deciduous for at least
a short period each year, the seasonality being related to a period of water stress and/or low
temperatures. The woodland canopy is from 6 to 20 m in height, and ranges from 20% cover to
almost closed-canopy forest.
Caesalpinoid woodlands are mostly found on nutrient-poor soils (except Colophospermum and
Acacia–Combretum woodland). Vegetation composition and structure are determined by climate
(rainfall amount, length of dry season, mean temperature, frost), position in the landscape and
soil type. Most changes in vegetation type within the ecoregion are gradual. Fire is an important
feature.
Another characteristic feature is the presence of large termite mounds, especially where sub-soil
drainage is impeded. These are composed of cation-rich (particularly calcium) soils owing to
their high clay contents, and generally have lower soil moisture levels. Termitaria support very
different species from the surrounding woodlands. Their presence, as nutrient-enriched 'islands',
is of major significance for both species diversity and woodland ecology.
2 Areas taken from version of original hand-drawn map of Timberlake, digitized by WWF SARPO GIS Unit in 2001.