Seeding for Postfire Rehabilitation

Historically, broadcast seeding of grasses, usually from aircraft, has been the most common postfire rehabilitation treatment.  Rapid vegetation establishment has been regarded as the most cost-effective method to promote water infiltration and reduce hillslope erosion (Noble 1965; Rice and others 1965; Miles and others 1989).  Despite persistent questions about the effectiveness of postfire grass seeding and its negative impacts on natural vegetative recovery, seeding remained a widely

Aerial Seeding

Because of the difficulty and expense involved in measuring hillslope erosion directly, most evaluations of seeding effectiveness have been reported in terms of ground cover or canopy cover produced, rather than any direct measurement of erosion reduction (Beyers 2004; Robichaud and others 2000).  The studies reviewed by Robichaud and others (2000), suggest that seeding does not assure higher plant cover during the critical first year after burning.  In nine seeding studies providing quantitative ground cover data, 60-70% ground cover needed for erosion reduction (Pannkuk and Robichaud 2003), was attained in less than one-fourth of the treated areas during the first growing season.  Beyers (2004), in an recent review of postfire seeding effectiveness, reported that when postfire seed growth provides enough cover to substantially reduce erosion (60-70%), it generally suppresses revegetation by naturally occurring species.

Seeding is often most successful where it may be needed least—on gentle slopes and in riparian areas. Janicki (1989) found that two-thirds of plots with more than 30% annual ryegrass cover were on slopes of less than 35%. He also noted that grass plants concentrated in drainage bottoms indicating that seed washed off the slopes during the first two storm events. Concentration of seeded species at the base of hillslopes was also observed by Loftin and others (1998).