D2. Combretum-Terminalia-Diospyros wooded grassland

Vegetation type D2 occurs in mosaic with mopane (E1/E2) and hill miombo (C2) throughout its range . The Combretum apiculatum/Terminalia stenostachya/ Diospyros kirkii association (vegetation type D2) is the most extensive vegetation type in this mosaic, as it occurs on the shallow, stony fersiallitic soils which cover the gentler slopes and flatter regions of the upper valley floor. Hill miombo (C2 subtype 2) occurs in isolated patches on the deeper soils of the ridge tops, while scrub miombo (C2 subtype 1) occurs on the thin rocky soils of the steeper slopes. Mopane woodland and scrub woodland (E1 and E2) occur on sodic or calcareous patches of soil dotted throughout the upper valley floor. Combretum-Terminalia-Diospyros wooded grassland, in mosaic with vegetation types E1, E2 and C2 occurs on the upper valley floor and in the foothills of the Muchinga mountains. Throughout its range this vegetation type is associated with gently sloping terrain with relief measured in tens of metres.

The soils associated with D2 wooded grassland are stoneless to very stony soils, over siltstone and grits, which may or may not be covered with a surface mantle of quartzoze stones. They are highly variable in texture but tend to be shallow, grey to reddish brown and moderately acid (pH 5.4-6.6).

Combretum-Terminalia-Diospyros wooded grassland is defined by a well-developed grass/herb layer scattered with small trees and shrubs covering 10% to 40% of the surface. It is heterogeneous in composition and form, grading into woodland in some areas and pure grassland in others. Dominant small trees are Diospyros kirkii, Terminalia stenostachya, Combretum apiculatum, Terminalia stuhlmannii, Combretum fragrans, Combretum zeyheri, Crossopteryx febrifuga and Pseudolachnostylis maprouneifolia. Shrub species include Bauhinia petersiana, Acacia hockii, Acacia gerrardii and Ximenia caffra subsp. caffra. On the shallow, stony soils of this habitat, the grass layer is well-developed and dominated by medium to tall, coarse grasses. Common species are Andropogon gayanus, A. schirensis, A. fastigiatus, Aristida scabrivalvis, Diheteropogon amplectens, Heteropogon contortus, Hyparrhenia anaemopaegma, Loudetia flavida, Monocymbium ceresiiforme, Sorghum versicolor and Zonotriche amoena. Bothriochloa bladhii, Sporobolus pyramidalis, Heteropogon contortus, Echinochloa colona and Setaria spp. are locally common in poorly drained areas. Subshrubs typical of this habitat are Xerophyta suaveolens, Pachycarpus lineolatus, Cissus cornifolia and Cyphostemma spp. Characteristic herbs include Ipomoea welwitschii, Pterodiscus elliottii, Chlorophytum sylvaticum, Lapeirousia eryantha, Raphionacme longituba, Neorautanenia mitis, Vernonia melleri, Tephrosia spp. and Gladiolus spp. Common ground herbs are Crotalaria cephalotes, Euphorbia oatesii, Gardenia subacaulis and Torennia spicata. Sumps and wet areas are characterised by Cycnium tubulosum and sedges including Ascolepis protea var. splendida, Kyllinga alba, Scleria bulbifera, Cyperus margaritaceus and Cyperus macrostachys.

Trapnell believed that this vegetation mosaic is the result of sheet erosion. He suggests that the colluvial soils of the escarpment were more extensive in the past, covering much of the upper valley floor in the NLNP. Evidence for this is to be found outside the park, north of the Lufila river, where miombo woodland covers a large area of the upper valley floor (Trapnell et al. 1950; Edmonds, 1976) and is found on soils of a colluvial nature containing laterite nodules. It is postulated that, in the NLNP and further south, much of this escarpment soil has been washed away, leaving a dissected, undulating terrain, the slopes of which are characterised by a thin, stony soil cover. This niche is occupied by vegetation type D2 in the areas of gentler relief and miombo scrub woodland (C2 subtype 1) on the steeper slopes. Hill miombo woodland (C2, subtype 2) occupies the ridge tops, where remnants of the deep escarpment soil cover remain. The patches of sodic or calcareous soil, associated with the mopane vegetation (E1/E2) of the upper valley floor, are almost certainly derived from ancient, and in some cases recent, termite activity (Trapnell et al., 1976).