Variation in Grassland Fuel Curing in South Africa

Abstract

Fire is critical to the maintenance of ecological function in many ecosystems worldwide, especially mesic sub-Saharan rangelands. But most rangeland fire research occurs in a wildfire context, is focused on fire effects, or simply assumes that grass-dominated fuelbeds are homogeneous. In this study, we sampled fuel moisture from several species in two grassland locations in South Africa to determine (1) if grassland fuels cure differently among species or across locations, (2) whether differences in curing meaningfully affect fire behaviour, and (3) if fuel moisture is associated with soil moisture. Data were characterised by high variability among sampling sites and dates, which highlights the importance of accounting for—rather than averaging out—variation with hierarchical analysis. Variability among locations and species indicates that broad similarities among plant communities do not adequately describe fuelbed dynamics. We observed patterns in the C3 Festuca costata that deviated from general patterns in C4 grasses, particularly in grasslands at the edge of environmentally determined transitions. These differences might have landscape-level implications under global environmental change. The temporal breadth and species-level specificity of our study constitute novel data that identify further research to improve the understanding of fuelbed ecology in grasslands worldwide, beyond the context of extreme fire weather and behaviour. Our data suggest that managers in South Africa and abroad should consider heterogeneity within grassland fuelbeds and recognize seasonal changes to ensure that objectives are obtainable ahead of burns, and to explain spatial variation in response within what might have appeared to be a homogeneous grassland fuelbed.