Impact of land use on vegetation composition, diversity, and selected soil properties of wetlands in the southern Drakensberg mountains, South Africa

Abstract

Wetlands provide the ecosystem services of enhancing water quality, attenuating floods, sequestrating carbon and supporting biodiversity. In southern Africa, the pattern and intensity of land use is influenced by whether land tenure is public (state), private (individual ownership), or communal (shared agricultural and grazing resources). The influence of land tenure and its associated use on service provision was compared for communal tenure (grazing, maize production), wildlife conservation, and commercial agriculture (grazing, planted pastures) in the southern Drakensberg. Ordination analyses revealed that oxbow marshes, hill slope seepages and hygrophilous grasslands, the main hydro-geomorphic units, supported distinct plant communities that differed in their response to land use because of wetness or slope. Oxbows, uncultivated because of wetness, were inherently species poor with few exotics. Composition of hill slope seepages, uncultivated because of saturated slopes, varied among tenure types most likely in relation to grazing pressure. Seepages were threatened by the exotic invasive Rubus cuneifolius. Eighty-five percent of hygrophilous grassland had been cultivated by 1953, most of which was subsequently abandoned to secondary grassland. Primary hygrophilous grassland and hill slope seepages were the main repository for indigenous plant diversity, while communal maize fields supported a diverse mixture of mainly exotic species. Soil carbon concentrations decreased from oxbows to pastures, seepages, primary hygrophilous grassland, secondary grassland, and maize on former grassland (7.0, 4.1, 4.0, 3.5, 2.4, and 1.7%, respectively). The pattern for total soil nitrogen and sulphur were the same. Cultivation of hygrophilous grassland was estimated to have reduced soil carbon stocks to 69% of pre-settlement levels by 1953 ($150 years BP). Stocks then increased by 8% to 2001 following crop abandonment. Cultivation has impaired water quality enhancement and flood attenuation because of greater amounts of bare ground and shorter vegetation. Further improvement of ecosystem services will depend on the influence of socio-economic factors on communal cropping.

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

“…Thus, in southern KZN, stocking rates that varied from low to high had no significant effect on plant species richness (Martindale 2007). Similarly, no significant difference in plant species richness was found between grassland wetlands on the Coleford Nature Reserve and on two nearby communal areas which had stocking densities several times higher than that on the Reserve (Walters et al 2006). No significant differences in plant species richness were found between the Cathedral Peak protected area and adjacent communal (lease) land, but differences in stocking densities between the two land-use types were uncertain (Peden 2004).…”

The Impact of Invasive Alien Plants on Rangelands in South Africa

“…This evidence suggests that well-managed rangeland is resistant to invasion. Wetlands were more severely invaded than drylands in this region; their total of 47 alien species included 6 of the 30 most abundant species, with wetlands in communal areas more densely invaded than those in commercial or protected areas (Walters et al 2006). By contrast, alien species were absent or very scarce on both sides of the fence in semi-arid areas.…”

Relating Biodiversity and Landscape Spatial Patterning to Land Ownership Regimes in Northeastern Mexico

“…Research into the relationship land tenure and biodiversity, concerning property rights and issues of control, access, and use of land, has been scarce (Mackenzie 2003). Our study contributes in analyzing whether private, public, or communal land ownership promotes sustainable management of natural resources (Walters et al 2006, Baland and Platteau 1996, Ostrom 1990). However, the concurrence of different land ownership types within our study region necessarily requires analysis of the broader socioeconomic and political contexts in which biodiversity conservation takes place (Goeschl and Igliori 2006).…”