Barb goatgrass is an invasive annual grass from the Mediterranean region that negatively affects both native plant biodiversity and the forage quality of grasslands. Prescribed burning may be the best landscape-level tool available to manage invasive species like barb goatgrass while also enhancing biodiversity, but few studies have quantified the long-term effects of fire on goatgrass and the rest of the plant community. We assessed the effects of fire on an invading front of barb goatgrass on a private ranch in Sacramento County, CA. We established burned and unburned treatment plots within the goatgrass-infested area and used prescribed fire to burn the treatment plots in June 2005. We monitored plant-community composition before burning and for 7 consecutive yr following the burn. Additionally, we tested the viability of goatgrass seeds in both burned and unburned plots. One year after the burn, goatgrass cover in burned plots was 3% compared with 21% in unburned plots. This reduction in goatgrass cover was still strong 2 yr after the burn (burned, 6%; unburned, 27%) and weaker but still statistically significant for 4 of the next 5 yr. The burn also reduced germination of goatgrass seed by 99% as indicated by seed-viability tests conducted in the laboratory. The native plant community responded positively to the burn treatment in the first year following the burn with an increase in native diversity in burned plots vs. unburned plots, but the effect was not detectable in subsequent years. Nonnative annual forb species cover also increased in the first year following the burn. Our study shows that a single springtime burn can result in a short-term boost in native species diversity, reduced seed germination of barb goatgrass to near zero, and reduced cover of barb goatgrass for at least 7 yr after the burn.
Nomenclature: Barb goatgrass, Aegilops triuncialis L.
Management Implications: We studied the long-term effects of a single, prescribed burn on barb goatgrass control and on native and nonnative species diversity in a grassland community in California. A single, late-spring burn reduced the cover of goatgrass for at least 7 yr following the burn. The burn had short-lived, positive effects on the native plant community with an increase in native plant cover and richness for a single year following the burn. The long-lasting effect of a single burn on the goatgrass was unexpected, given other research, which suggests that 2 consecutive yr of fire treatment are required for significant control. We suspect that this burn was particularly effective because it was conducted during a year with high fuel loads, which allowed ground temperatures to reach levels necessary to effectively kill the goatgrass seeds as they fell to the ground in the inflorescence. Our germination study confirmed that the fire effectively reduced the germination rate of seeds contained within intact, but burned, spikelets to near zero. It is rare for a study to track a management treatment for more than 2 to 3 yr, but our results demonstrate that there is great value in doing so. Prescribed burning is a very costly and risky treatment to implement, so understanding how well it works and how often a site should be burned to control the target species is very useful for decision makers. We were also able to document a distinct trend in goatgrass and native species cover over that period and to evaluate how that trend aligned with climatic data like rainfall. In fact, we believe total rainfall amounts may have affected the goatgrass in two ways: high rainfall in the year of the burn produced above-average biomass, which fed a hotter and more-complete burn, and low rainfall starting 3 yr after the burn may have reduced the cover of goatgrass in both burned and unburned plots, potentially prolonging the fire’s effect.