Spatial scales influence long-term response of herbivores to prescribed burning in a savanna ecosystem

Abstract

Both wild and prescribed fire in savanna ecosystems influence habitat use by herbivores by creating or maintaining spatial and temporal heterogeneity in forage quality and vegetation cover. Yet little is known about how spatial scales influence long-term persistence of fire effects. We examined changes over a 6-year period in herbivore preference for experimentally burned patches that varied in spatial extent and grain. Avoidance for the burns by elephants and preference for the burns by impala and Grant’s gazelle decreased significantly. For the rest of the species (zebra, eland, oryx, hartebeest, warthog and hare), there were no significant changes in preference for the burns. Changes in preference for the burned areas depended on the spatial extent and grain of the burn, with intermediate-size (9-ha) burns and large (8-ha) patchy burns being more preferred 6–7 years after fire. Grain, but not the spatial extent of the burned area, influenced changes in grass height. Fire resulted in a delayed reduced tree density irrespective of the spatial scale of the burn. Results of this study indicate that, depending on the scale of fire prescription, the impacts of fire on herbivores may last longer than previous studies suggest.

The effects of fire frequency on vegetation structure and mammal assemblages in a savannah‐woodland system

“…Additionally, continued frequent fires may decrease soil nutrients and plant forage quality over time (Anderson et al, 2007; Blair, 1997). Nonetheless, Kimuyu et al (2017) found herbivore preferences for burnt areas can still be seen many years after a fire, potentially explaining the increased preference for open‐structured, frequently burnt plots shown by the pure grazers sable antelope, waterbuck, buffalo and plains zebra in this study, as found elsewhere (Burkepile et al, 2013, 2016; Kingdon et al, 2013; Mandinyenya et al, 2020; Traill, 2004; Wirtz & Kaiser, 1988). Similarly, the mixed‐feeding impala showed a strong preference for frequently burnt plots in this study (Ford et al, 2014).…”

“…Although the broad trends in mammal responses to resource gradients (Hopcraft et al, 2010) and the immediate response of mammal species to fire have been well‐studied (Eby et al, 2014; Green et al, 2015; Sensenig et al, 2010; Zavala & Holdo, 2005), different species may also respond differently to the longer‐term effects of fire (Bell, 1971; Kimuyu et al, 2017). Understanding mammal responses to differences in long‐term mean fire frequency is thus necessary for the management and conservation of species and habitats.…”

Effects of large mammalian herbivory, previous fire, and year of burn on fire behavior in an African savanna

“…Modeling of fire–herbivory interactions in a different grassland ecosystem suggested that herbivory reduced fire behavior more than previous fire alone, but these differences declined with time, and disappeared for some fire metrics within 3–4 years (Starns et al, 2019). In a separate set of burn experiments in this ecosystem (Sensenig et al, 2010), both 1‐ha continuous and patchy (30 × 30 m) burns were no longer attractive to herbivores 6–7 years after fire (Kimuyu et al, 2017). Intermediate‐size burns 9‐ and 81‐ha patchy were the most attractive, while large‐size 81‐ha continuous burns were less attractive.…”

Synergistic effects of long‐term herbivory and previous fire on fine‐scale heterogeneity of prescribed grassland burns

“…The interactions between fire and herbivory on fuel loads and fire impacts are likely dependent on the spatial scales of these processes (Collins and Smith 2006, Kimuyu et al 2017). Most studies have examined fire–herbivory impacts on fuel loads at intermediate to landscape‐level scales (Waldram et al 2008, Hempson et al 2019).…”