Can heavy grazing on communal land elevate plant species richness levels in the Grassland Biome of South Africa?

Abstract

A common perception, particularly in South Africa, is that heavily and continuously grazed communal land leads to degradation and loss of plant diversity when compared to commercial rangeland farming or conservation areas. We focus on whether this applies to the Grassland Biome of South Africa and whether the opposite can occur, namely, an increase in plant species richness under heavy grazing. A study of a contrast between a communal area of the former Ciskei and a neighbouring nature reserve showed that intense utilization under communal use led to a significant increase in plant species richness. However, this increase was scale-dependent with the greatest significant difference occurring at sample plot scale (50 m 2 ) but converging at the broader scale of the whole study site. Species that increased with heavy grazing included those from arid Karroid areas as well as some from more mesic grassland and savanna areas. The contribution of beta diversity to gamma diversity across the grazing contrast was relatively low which reflects the relatively high proportion of species shared between treatments. Total plant canopy cover declined sharply with heavy grazing. In terms of plant canopy cover, grazing favoured annual over perennial plants, prostrate over erect plants, and stoloniferous over tussock plant architecture. This pattern was not supported when expressed in terms of number of species belonging to these grazing response groups or traits.

Herbivore-Driven Land Degradation: Consequences for Plant Diversity and Soil in Arid Subtropical Thicket in South-Eastern Africa

“…In terms of an inverse measure of turnover, percentage species similarity between individual plots on LU and HU was a meagre 2 per cent compared with the 15 and 18 per cent similarity at thicket contrasts of Hoffman and Cowling (), and calculated in the same way, thus indicating a much higher turnover on our study site. The species turnover on our thicket site was also higher than that on other similarly sampled degradation sites in our pilot study elsewhere, with lowest turnover found in the Savanna and Grassland Biomes (Rutherford and Powrie, ; Rutherford et al ., ). Our results suggest that there is thus a high reliance on the availability of replacement species from a different species pool for degraded thicket.…”

“…The inadequate understanding of the relationship between land degradation and biodiversity loss has been shown, for example, by the South African National Spatial Biodiversity Assessment (Rouget et al ., ) in which the threats and impact of habitat degradation on biodiversity were omitted owing to uncertainty of the implications of degradation effects for local and regional biodiversity. This omission prompted the South African National Biodiversity Institute to initiate a pilot research programme to assess the impact of severe degradation on plant diversity across the biomes of South Africa (Rutherford and Powrie, , , ; Rutherford et al ., , ). This paper on part of the Subtropical Thicket Biome represents a contribution to that programme.…”

Moderate grazing sustains plant diversity in Afromontane grassland

“…Although the unimodal response of species richness to increasing grazing intensity persisted across spatial scales in our study, we saw a larger number of non‐significant effects at site level. Plant species richness of areas with light and heavy grazing also converged at larger spatial scales, despite significant differences at smaller spatial scales in South African rangeland (Rutherford & Powrie ). It is possible that drivers impacting species assemblages at larger spatial scales are not the same as those at small spatial scales.…”

Understanding relations between pastoralism and its changing natural environment

“…The increased species richness with higher grazing intensity is consistent with Nacoulma et al (2011) in West Africa, Oba et al (2001) in open grazed lands in Kenya and with Rutherford and Powrie (2011) in communal lands of South Africa.…”