EFFECTS OF CATTLE GRAZING, GLYPHOSATE, AND PRESCRIBED BURNING ON FOUNTAINGRASS FUEL LOADING IN HAWAI'I

Crimson fountaingrass (Pennisetum setaceum) is a nonnative invasive grass that has occupied a significant portion of the western side of the island of Hawai`i. As a result, several fires in excess of 4,049 ha have occurred in the area over the past 20 y. We are studying the effectiveness of cattle grazing, aerial application of glyphosate herbicide, and prescribed burning to reduce the fuel loading of fountaingrass in this dry, tropical setting. Grazing and prescribed burning were applied as whole-plot treatments to plots ranging in area from 2.4 to 6.5 ha; glyphosate herbicide was aerially applied as a split-plot treatment. Plots were burned in January and February 2004, aerially sprayed in March and May 2004, and grazed by cattle in March and April 2004. Fuels were sampled prior to treatment and at periodic intervals over the first year following treatment. Fuel and fire behavior variables were measured during the prescribed burns. Pre-treatment fuel loading ranged from 9 to 11 Mg/ha and fuel height averaged 0.5 m. Observed dead fuel moistures were 12-16% and live grass fuel moisture was > 270% during the prescribed burns. Fire spread rates up to 16.8 m/min and flame heights up to 3.7 m were observed. Prescribed burning and glyphosate reduced fuel loads by 46% and 14%, respectively. Fuel height was reduced by 8-48%. Grazing did not have a significant effect in this study. Fuel height did recover and fuel loads did not recover to pretreatment levels within 13 mo of the prescribed burns.