Downy brome (Bromus tectorum L.)—dominated communities can remain as stable states for long periods, even with frequent disturbance by grazing and fire. The objective of this study was to determine the effectiveness of using targeted cattle grazing and late-season prescribed burning, alone and in combination, to reduce B. tectorum seed bank input and seed bank density and thus alter aboveground community dynamics (species composition) on a B. tectorum–dominated landscape in northern Nevada. Cattle removed 80 to 90% of standing biomass in grazed plots in May of 2005 and 2006 when B. tectorum was in the boot (phenological) stage. Grazed and ungrazed plots were burned in October 2005 and 2006. The combined grazing–burning treatment was more effective than either treatment alone in reducing B. tectorum seed input and seed bank density, and in shifting species composition from a community dominated by B. tectorum to one composed of a suite of species, with B. tectorum as a component rather than a dominant. This study provides a meso-scale precursor for landscape-scale adaptive management using grazing and burning methodologies.
Nomenclature: Downy brome; Bromus tectorum L. BROTE.
Management Implications: Livestock grazing, the invasion of downy brome, and the resulting grass-fire cycle have played major roles in the conversion of sagebrush–grassland and other native plant communities to downy brome–dominated landscapes. Grazing and fire, if properly managed, can also play major roles in suppressing downy brome and changing plant community composition. This investigation was aimed at determining if targeted cattle grazing and prescribed burning, alone and in combination, could reduce downy brome reproductive potential, and thus its dominance in a degraded sagebrush–grassland community. In this study, we found that intensive cattle grazing in May, when downy brome was in the boot stage (just before inflorescence emergence from the culm), reduced seed input into the seed bank (Figures 1 and 2). Prescribed burning in October consumed much of the litter on the soil surface, killing or damaging many downy brome seeds suspended in the litter and reducing the number of favorable microsites for germination and establishment of surviving seeds in the soil. The integration of targeted grazing with prescribed burning was more effective than either treatment alone in reducing downy brome seed bank density and changing species composition from a community dominated by downy brome to one dominated by less flammable species such as Sisymbrium altissimum (Figures 1 and 3). Although S. altissimum is less flammable than downy brome the potential for fire spread is still present because of the tumbling nature of S. altissimum. Thus, our methodologies created a less fire-prone plant community, not a fireproof community. These findings are encouraging; the required stocking density for intensive grazing and the short temporal window for grazing during the boot stage will limit the use of targeted grazing to relatively small scales, i.e., about 42 ha during one growing season for a herd of 500 cow–calf pairs. And, managers must recognize that the effects of grazing and prescribed burning treatments are short-lived (1 to 2 yr); thus, treatments must be integrat