Impacts of postfire grass seeding on vegetation recovery in southern California chaparral

Abstract

Postfire grass seeding as an attempt at erosion control on chaparral slopes has been a common practice for decades. Annual ryegrass (Lolium multiflorum) has been most frequently used. Critics point out that ryegrass can suppress native species and may reduce shrub seedling survival. In 1986, we began investigating the impacts of seeded ryegrass on chaparral regeneration. We gathered prefire vegetation data on sites scheduled to be burned in wildfire-intensity prescribed fires. After four prescribed fires and a wildfire, half of the vegetation plots at each site were seeded with annual ryegrass, and vegetation cover, composition, and shrub seedling density were measured each spring for 5 years. At only one site was average total herbaceous plant cover significantly greater on seeded plots than on unseeded plots. At all sites, average herbaceous plant cover other than ryegrass was less on seeded plots in at least one postfire year. Mean shrub seedling density was never significantly different between seeded and unseeded plots. After 5 years, surviving shrub seedling density appeared to be sufficient to replace plants killed by fire. Our results suggest that seeded ryegrass has a greater impact on the chaparral postfire herbaceous flora than on shrub seedling regeneration in southern California.

Citation

Beyers, J.L.; Wakeman, C.D.; Conard, S.G.; Wohlgemuth, P.M. 2002. Impacts of postfire grass seeding on vegetation recovery in southern California chaparral. Association for Fire Ecology Miscellaneous Publication No. 1: 318-323.