Functional Responses of South African Rangelands in Contrasting Tenure Systems

Land degradation in South African rangelands has frequently been studied in the context of tenure systems, because both governmental policy and range management practices were historically implemented in contrasting forms. We compared the functional response of vegetation along grazing gradients between a communal (CU) and commercial (CO) farming areas. One transect was established per farm from the waterpoint to a mid-field position. Six equally spaced plots (5 m × 5 m) were set up along each transect. Using a taxon-free sampling procedure, we recorded the response of 15 community-aggregated plant functional traits (CPFT) in: (1) mature standing biomass; and (2) after four weeks’ regrowth following clipping. Additionally, species identity was recorded. Grazing on CU was continuous and stocking rate not controlled, while CO applied rotational grazing with recommended stocking rates. From the results, CPFT differences were not significant (Student’s t-test, P \u3c 0.01) between tenure systems. A principal component analysis of CPFT showed largely overlapping functional responses in the two tenure systems in the case of mature standing biomass, while the functional response of regrowing vegetation was clearly separated in the ordination space. Communal rangelands had twice the species richness of commercial farms.We concluded that, from a functional perspective, communities under different tenure systems were similar. However, the functional response of vegetation regrowth might be different as well as the ecological services provided (biodiversity)

Response of community-aggregated plant functional traits along grazing gradients: insights from African semi-arid grasslands

Questions: Plant communities fulfil key functions in the ecosystem, which can be characterized by their plant functional traits. In functional ecology, plant communities are considered to hold a set of trait attributes reflecting a specific plant strategy adapted to persist in the environment to which they are exposed. In semi-arid grasslands of the Republic of South Africa, we addressed the following questions: how are community-aggregated plant functional traits (CPFT) shaped by grazing gradients; which plant strategies are associated with the response of CPFTs; and are environmental factors, such as soil properties and grazing management, interrelated with the functional response of vegetation to grazing gradients? Location: Semi-arid grasslands close to Thaba Nchu, Free State (Republic of South Africa). Methods: Piosphere transects from a water point into the field were established to portray grazing gradients on two communal grazing areas with continuous grazing and two commercial farms with rotational grazing. Along each transect, six plots (5 x 5 m) were evenly distributed. The trait-transect sampling was applied to record 12 CPFT related to light capture and forage quality. A redundancy analysis was performed to derive relationship between CPFTs, grazing gradients and environmental conditions. Results: Grazing intensity decreased along piosphere transects, from the water point into the field. Most CPFTs responded to this decreasing gradient of grazing intensity and so allowed derivation of trait syndromes that clearly reflect plant strategies of ruderal and competitive vegetation. Close to water points, plants had higher nitrogen concentrations, fewer cell wall components and higher specific leaf area, hence light capture might be faster and more efficient per leaf area and leaf mass. Plant communities exposed to intensive grazing were well adapted to defoliation, trampling and nutrient accumulation through fast growth rates and a quick return strategy. Conclusions: In the sacrifice zone around water points, there is an ecological niche for vegetation communities exhibiting a strategy of fast growth, which is well adapted to intense and frequent grazing and is also associated with forage of high nutritional quality