干旱区生态环境知识资源中心

Invasive annual grasses have become increasingly important components of desert vegetation in North America. They are especially problematic because they increase the extent, severity, and frequency of fire in desert shrublands that normally experience fire very rarely, or not at all. After fire, invasive grasses and forbs are often dominant and restoration methods are required to promote native plant recovery. Three treatments to control invasive annual grasses and forbs were implemented in the first 3 years following a fire in creosote bush scrub vegetation. Treatments included early season mechanical removal (raking) of all annuals, grass-specific herbicide (Fusilade II), and Fusilade II plus hand pulling of exotic forbs. In the first year, all treatments reduced invasive annual grass abundance by about half but had little effect on native annuals. Treatment effectiveness was minimal in the first year due to low and irregular distribution of rainfall. In the second year, insufficient rainfall prevented the germination of any annual plants and no treatments were applied. In the third year, precipitation onset occurred later in the season and was above average. Although the raking treatment performed poorly, treatments utilizing Fusilade II nearly eliminated invasive grasses and forbs, achieved native annual dominance, and increased native perennial abundance. These results indicate that in the absence of invasive grasses and forbs, the native annual community can be resilient to fire disturbance and native perennials can recover. The results also suggest that burned creosote bush shrublands can be managed after fire to decrease the chance of invasive plant-fire feedback.