Fertilization and Seeding Effects on Vegetative Cover After Wildfire in North-Central Washington State

Abstract

Abstract Land surface treatments are often applied after severe wildfires to mitigate runoff and erosion threats. However, questions remain about treatment effectiveness, even as treatment costs continue to rise. We experimentally evaluated the effects of seeding and fertilization treatments on vegetative and total soil cover for two growing seasons after the Pot Peak wildfire in the eastern Cascade Mountains. Without treatments, vegetative cover averaged 15% the first year and 27% the second year after wildfire. Fertilization significantly increased vascular plant cover and reduced bare soil area in both years, but differences between low and high fertilization levels were not significant. Fertilization also increased cryptogam cover. Seeding alone was generally ineffective; however, the combination of fertilization with a seed mixture containing the native forb, yarrow (Achillea millefolium L.), produced the highest vascular plant cover and lowest bare soil area. Our results suggest that fertilization may be more effective than seeding, probably providing a degree of protection from erosion, especially the second year after fire. However, treatment effectiveness must be evaluated in context against costs and potential ecosystem impacts.