Effects and Effectiveness of Seeding Following High-Severity Wildfires in Northern Arizona Ponderosa Pine Forests

Seeding following high-severity wildfires is intended to reduce water runoff, soil erosion, and non-native species invasions. Post-wildfire seeding treatments most commonly use seed of non-native annual cereal grains selected for quick growth and abundant root systems. U.S. policy recommends the use of native seed, but adequate supplies of locally collected seed are rarely available. Seeding following wildfires for erosion control is based on the positive correlation between bare ground and increased sedimentation rates, and the negative correlation between vegetative (or ground) cover and runoff and erosion rates. Seeding to prevent non-native species invasions is based on the concept that seeded species will quickly co-opt resources and exclude non-natives. Critics of seeding following wildfires argue that seeding rarely achieves the cover levels needed to effectively reduce runoff and erosion; when treatments do achieve high levels of cover, it comes at the expense of native plant regeneration. Due to the stochastic nature of wildfires, well-replicated studies with adequate control areas have been rare. I used a controlled, replicated, and randomized experimental design to test the effects and effectiveness of native and non-native seeding following three high-severity wildfires in Arizona ponderosa pine (Pinus ponderosa C. Laws.) forests. I found seeding with either non-natives or native species: (1) was generally ineffective in producing the levels of vegetative cover associated with reduced runoff and erosion; (2) significantly altered plant community composition; and (3) did not reduce abundance of non-native species. My results add to the growing evidence that seeding following high-severity wildfires does not achieve management objectives of providing high vegetative cover associated with low soil loss and suppression of non-native species. Seeding also altered post-fire plant community composition through reductions in native species, including perennial native forbs, shrubs, and colonizing annual/biennial species. The high financial cost and low potential for effectiveness should call into question the continued practice of seeding areas burned in high-severity wildfires