**4. Spatial heterogeneity**

Spatial heterogeneity of resources, and particularly the seasonal separation of resource use, leads to distinction between equilibrium (static events) and nonequilibrium(stochastic events) [10]. Similar results obtained by Sainge et al. [11] reported that the changes in species composition, vegetation structure, and diversity across environmental and geographic gradients vegetation structure are influenced strongly by elevation [12]. Factors controlling the spatial distribution of grazing pressure may be less familiar to some ecologists [13]. Changes in spatial heterogeneity caused by grazing imply changes in habitat diversity and influence the diversity of consumers ranging from insects to birds and mammals.

Selective grazing under continuous pattern is a common grazing pattern in most arable lands that have been affected by degradation in South African pastoral farming system. The literature has reported various experiments and interesting results. Some of the findings indicate that strategies and techniques to enhance biomass production must be geared around water conservation, soil management practices, protective irrigation, and maximizing the use of fertilizers, indigenous crop varieties [14].

Equilibrium areas are referred to as those areas in which animals are in some sort of balance with their resources because of their dependence on them during the dry season. Climatic variation will cause a balance to fluctuate annually. None equilibrium areas support animals in the season of plant regrowth but the size of the animal population is not determined by these resources [15]. It is on these non-equilibrium areas that variable and periodically high defoliation intensity may be imposed because of climatic variation, causing fluctuations in the ratio of animal population size to resource abundance.

Vegetation use during the dry season range is unlikely to suffer such impacts because there is a likelihood of such vegetation being insensitive to defoliation during dry season. Vegetation cover plays important role in preventing soil cover from land degradation [3].

Together with spatial localization of herbivore impacts, due to seasonal grazing behavior and plant species, and patch-level selection, this is likely to make these environments more, and not less, prone to ecological changes [5]. Ecologists and policymakers should seek to identify the characteristics of grazing systems that predispose such systems to veld degradation, while others appear to be resistant [16].
