Post-wildfire regeneration of rangeland productivity and functionality – observations across three semi-arid vegetation types in South Africa

Abstract

Wildfires can have significant impacts on rangeland productivity and functionality causing substantial economic losses to affected farmers. In August 2011, such wildfires swept through the North West province of South Africa, destroying large areas of grazing and farm infrastructure. There is little information available on how the regional semi-arid rangelands respond to fire. In order to increase knowledge on short-term regeneration capacities of burned rangelands, the recovery of grass phytomass, composition and diversity as well as the frequency distribution of patch types (i.e. grass-, litter-and bare patches) were assessed in the growing season following the fire. Burned and unburned sites were compared in two regional grasslands and one savanna type receiving between 480 and 700 mm rainfall y −1 . Fire significantly reduced phytomass production, and lowered the grazing capacity and potential grazing days across vegetation types. In general, grass diversity, composition and relative frequencies remained unaffected documenting an overall good regeneration potential of the grass sward. An increased proportion of bare patches and decrease of litter indicated that the post-fire environment lost functionality with respect to erosion control, nutrient cycling and water infiltration. Gained insights provide valuable baseline information for future impact assessments and research into the fire dynamics of investigated vegetation types.

Short-Term Responses of Southern African Semi-Arid Rangelands to Fire: A Review of Impact on Plants

“…Various burning regimes do not appear to fundamentally change the composition of rangelands (Tainton and Mentis, 1984;Snyman, 2005b;Breedt et al, 2013), although both the frequency of defoliation by fire and the season of burning can cause shifts in the relative abundance of constituent species (Morris and Fynn, 2001). Most grass species in these drier areas are, therefore, relatively adapted to survive the impact of fire.…”

“…It has generally been assumed that fire should be excluded from these arid and semi-arid rangelands (Tainton and Mentis, 1984;Snyman, 2003a;Breedt et al, 2013); especially as grazing itself improves forage quality (Snyman, 2003b). By contrast, few researchers argue that in some arid and semi-arid areas, fire can be an effective tool in managing for forage production improvement (Everson, 1999;Pérez et al, 2008).…”

“…Depending on the climatic conditions and post-fire management, accidental, runaway, or wildfire will influence both productivity and functionality of the rangeland ecosystem over the short-term (Snyman, 2004a;Trollope, 2009;du Toit et al, 2014). These fire effects could also have a major residual effect on the next growing season's vegetation productivity (Knapp and Seastadt, 1986;Breedt et al, 2013).…”

“…Fire is regarded as a central component in the management of the higher rainfall, sourveld (>600 mm, mesic) rangelands (Hardy et al, 1999;Trollope, 1999;Vermeire et al, 2014); nevertheless, its role in the drier sweetveld (<600 mm, arid and semi-arid) systems is less well-known (Scheintaub et al, 2009;Breedt et al, 2013;Vermeire et al, 2014). It has generally been assumed that fire should be excluded from these arid and semi-arid rangelands (Tainton and Mentis, 1984;Snyman, 2003a;Breedt et al, 2013); especially as grazing itself improves forage quality (Snyman, 2003b).…”

“…The complexity of fire impact on vegetation dynamics and soil quality is based on different aspects, namely, fire type (Booysen and Tainton, 1984) and frequency (Bond and Keeley, 2005;Kirkman et al, 2014); the application of different grazing patterns following the fire (Knapp and Seastedt, 1986;Snyman, 2006a); rainfall variability (Snyman, 2003a;Joubert et al, 2013); seasonality of climate (Joubert et al, 2013); landscape heterogeneity (Turner et al, 1997;Breedt et al, 2013); and vegetation type (Killgore et al, 2009). The controversy of repeated fire's impact on desert grassland, without trees, lies in the adaptability and sustainability of this sensitive vegetation (Killgore et al, 2009;Liang et al, 2009).…”