Short-Term Control of an Invasive C4 Grass With Late-Summer Fire

Abstract

Yellow bluestem (Bothriochloa ischaemum [L.] Keng var. songarica [Rupr. ex Fisch & C.A. Mey] Celarier & Harlan) is a non-native, invasive C4 grass common in southern Great Plains rangelands. We measured the effects of a single late-summer (September 2006) fire on yellow bluestem at two sites in central Texas (Fort Hood and Onion Creek). At Fort Hood, relative frequency of yellow bluestem in burned plots decreased from 74 ± 4% (preburn; mean ± standard error) to 9 ± 2% (2007) and remained significantly lower compared with unburned plots through 2009 (burned: 14 ± 2%; unburned: 70 ± 14%). At Onion Creek, yellow bluestem initially decreased from 74 ± 5% (2006) to 32 ± 7% (2007). Yellow bluestem recovered substantially by 2009 (67 ± 10%) but was still significantly lower than in unburned transects (96 ± 1%). Relative frequency of other graminoids increased significantly in burned plots (compared with preburn values) at Fort Hood (preburn: 11 ± 4%; 2009: 29 ± 7%) but not at Onion Creek (preburn: 24 ± 6%; 2009: 22 ± 7%). Frequency of forbs increased dramatically in the first growing season after fire (Fort Hood: 15 ± 2% to 76 ± 3%; Onion Creek: 2 ± 2% to 45 ± 5%), then decreased through the third growing season (Fort Hood: 57 ± 6%; Onion Creek: 11 ± 4%). Key differences between the sites include much higher biomass at Fort Hood than at Onion Creek (8 130 kg ⋅ ha-1 vs. 2 873 kg ⋅ ha-1), more recent grazing at Onion Creek (ending in 2000 vs. before 1996 at Fort Hood), and higher rainfall after the Onion Creek burn (214 mm in 20 days vs. 14 mm). Late-summer fire can temporarily decrease yellow bluestem frequency, but effects vary with site conditions and precipitation. Restoring dominance by native grasses may require additional management.