F1. Chloris-Dactyloctenium-Echinochloa grassland

Chloris-Dactyloctenium-Echinochloa grassland takes the form of short, annual grassland punctuated with occasional clumps of Combretum obovatum thicket. This vegetation type is found on degraded mopane woodland and, as a result, is often scattered with the skeletons of dead mopane trees. Vegetation type F1 covers a large area of the NLNP (approximately 335 km²) and is found on recently deposited alluvial soils adjacent to the Luangwa river. The terrain is flat and low lying, and is seasonally waterlogged during the rainy season.

Soils associated with this habitat tend to be shallow, poorly drained, light grey, compacted neutral sandy clays or sandy loams.

The important grasses in this habitat are short to medium-sized, nutritional species such as Chloris virgata, Dactyloctenium aegyptium, Dactyloctenium giganteum, Urochloa mossambicensis, Digitaria acuminatissima and Eragrostis gangetica. Echinochloa colona, Brachiaria deflexa and Sporobolus pyramidalis favour the wetter sites in this habitat. Typical herbs are Ammocharis tinneana, Crinum minimum, Leonotis nepetifolia, Senna absus, Indigofera gairdnerae (ground herb), and in the wetter areas, Heliotropium spp., Cycnium tubulosum and sedges such as Ascolepis protea var. splendida and Cyperus macrostachyos.

Chloris-Dactyloctenium-Echinochloa

secondary grassland (F1) is clearly part of a dynamic succession. The extensive areas of F1 grassland present in the NLNP today were not recorded by Astle in 1965. At that time, these areas were largely covered by mopane woodland. It is probable that this succession has arisen due to extensive browsing damage in mopane woodlands, concomitant with the well documented increase in elephant numbers recorded in the valley during the 1970’s (Caughley, 1976). Additional factors such as waterlogging and fire may have been involved in maintaining the grassland state. Recent observations made by the surveyor suggest that mopane seedlings are starting to re-invade the F1 grasslands in certain areas of the park. This reversion to mopane woodland would be consistent with the hypothesis that these grasslands are created and maintained by elephants because, as stated above, elephant numbers in the Luangwa valley have declined drastically in the past ten years (Leader-Williams et al. 1990). Furthermore, recent anti-poaching efforts have greatly reduced the incidence of man-made fires in the park. The mechanics of this succession need to be understood because Chloris-Dactyloctenium-Echinochloa secondary grassland is a particularly productive habitat, which aerial survey has shown is utilised by large numbers of grazers (NLCP census 1994). If these grasslands revert back to mopane woodlands, an important grazing habitat will be lost from the NLNP. Further research is needed to investigate the grassland-mopane succession, and the factors which influence it.