Influence of grazing and vegetation type on post-fire flammability

Abstract

Summary1. Natural area managers use fire and grazing to achieve nature conservation ⁄ production goals and to prevent the loss of life and property. Yet, little is known of the effects of post-fire grazing on fuel load and the proportion of days on which fire can be sustained (fire potential). This knowledge could help managers in planning interventions to achieve their goals. 2. At seven sites in Tasmania, Australia, including sedgeland, heathy forest and grassland, fire potential and fuel load were measured before, and for 2 years after fire. Measurements were made in burning, fencing and burning plus fencing treatments, and in control quadrats. 3. Burning followed by grazing, largely by native vertebrates, resulted in lower fuel loads than either grazing by itself or burning by itself. A new steady state was established in two grasslands. Fire potential at the oligotrophic sites was largely a function of time elapsed since the last fire, while at grassy sites was increased by grazing without fire, but depressed or slightly increased by grazing after burning. 4. Synthesis and applications. Effects of grazing after burning on flammability are not predictable from the single or additive effects of grazing and burning, varying between vegetation type and environment. In highland grassy ecosystems fire potential can be reduced by excluding grazing animals after fire, while in scleromorphic ecosystems grazing after fire does not affect fuel or fire potential. Intense grazing after fire can cause an, often desirable, shift from tussock to lawn grassland. Burning and subsequent grazing of tussock grassland vegetation in the lowlands may reduce the chance of wildfire damaging property and conservation ⁄ production values, while in highland tussock grassland burning followed by grazing will be largely ineffective in reducing the already low chance of such damaging fire.

Surface Temperatures and Durations Associated with Spring Prescribed Fires in Eastern South Dakota Tallgrass Prairies

“…Many studies suggest grassland fuel loads do not accumulate in a linear manner. Vegetation biomass can reach prefire levels in a minimum of 2 y (Morgan, 1999;Prober et al, 2007;Fidelis et al, 2010;Kirkpatrick et al, 2011;MacDonald and McPherson, 2011), although little or no further build up may occur if return times are greater than four or more years (Govender et al, 2006;Oluwole et al, 2008;Cianciaruso et al, 2010).…”

“…Grazing used in combination with fire increases grassland species diversity (Collins et al, 1998) and effectively manages invasive plants (Davies et al, 2009;Diamond et al, 2009;MacDonald and McPherson, 2011). Although grazing removes less plant biomass than fire, grazed lands have lower fuel loads than ungrazed areas (Savadogo et al, 2007;Davies et al, 2009;Diamond et al, 2009;Leonard et al, 2010;Kirkpatrick et al, 2011;MacDonald and McPherson, 2011), which may reduce the initial effectiveness of fire to kill undesirable vegetation. The combination of frequent fires, with grazing between fire events, can further reduce post treatment fuel accumulation (Archibald et al, 2005;Kirkpatrick et al, 2011); the unintended consequence can be milder fire conditions compared to areas managed with either method alone.…”

“…Although grazing removes less plant biomass than fire, grazed lands have lower fuel loads than ungrazed areas (Savadogo et al, 2007;Davies et al, 2009;Diamond et al, 2009;Leonard et al, 2010;Kirkpatrick et al, 2011;MacDonald and McPherson, 2011), which may reduce the initial effectiveness of fire to kill undesirable vegetation. The combination of frequent fires, with grazing between fire events, can further reduce post treatment fuel accumulation (Archibald et al, 2005;Kirkpatrick et al, 2011); the unintended consequence can be milder fire conditions compared to areas managed with either method alone. Similar to fire, the effects of grazing management on fuel loads may be negligible beyond 2 to 3 y (Archibald et al, 2005;Kirkpatrick et al, 2011;MacDonald and McPherson, 2011).…”

Goat grazing as a wildfire prevention tool: a basic review

“…The technique also requires further research, since information about grazing for fuel reduction is anecdotal and there is only limited scientific information currently available, mainly for the Mediterranean area (Nader et al 2007, Kirkpatrick et al 2011.…”

“…The high stock density in such a small space creates many trails, which act as minifuel breaks that help break up the continuity of available fuel (Mendenhall 2004, Kirkpatrick et al 2011.…”