the vegetation types and veld condition - Maremani Nature Reserve

Introduction
CHAPTER 5
VEGETATION STRUCTURE
The primary elements of vegetation structure are growth form, stratification and cover. Vertical structure is
a function of different growth forms (or size classes) dominating certain layers and can be expressed in
terms of canopy cover and/or density of each growth form. Density also indicates the spatial distribution of
different growth forms, populations or individual species. Vegetation can be classified according to
structure without reference to species names, and layer or size class diagrams can be used to illustrate
structure by using for example cover or density of each layer.
Size classes are considered to be good indicators of browse quality and quantity. Although a plant
community is defined to have a relatively homogeneous floristic composition, structure and habitat,
different floristic communities can have the same structure or vice versa. Structure can also relate to the
feeding pattern of animals as well as the suitability of a habitat for different animal species. The available
leaf mass and volume at different height levels are valuable in determining the suitability of a habitat for
browser species.
Density of the woody species can affect the condition of the herbaceous layer. Several studies have
indicated that the grass production declines when the tree and shrub density exceeds 1500 individuals
per hectare.
Cover
The mean percentage canopy cover and the variation within the communities for different strata and
vegetation types are summarised in Table 7 and Figures 3 & 4. The percentage cover of the high tree
stratum is the lowest in communities 1, 2, 9, 11, 14 and 15, representing the communities on rocks,
calcareous soils and disturbed areas (old fields)(Figure 3). Tree cover was higher tha 15% in communities
7, 8, 9, 11 and 12, while communities with a dense shrub layer are communities 2, 10, 11 and 12. The
highest grass cover was found in the south-east on the footslopes of the gneiss and sandstone hills
(community 6), as well as in the old fields along the major rivers and the riverine communities
(communities 15, 16 and 17)(Figure 4). Forbs were abundant in areas where calcrete occurs, for example
community 9. It is apparent that the communities with the lowest shrub and rock cover were associated
with a high grass cover (communities 6, 15, 16 and 17).
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