Seeds of change: A comparison of seeding vs. natural recovery for post-fire rehabilitation in a ponderosa pine forest

Background/Question/Methods   Fire was historically a common and necessary disturbance for rejuvenating and diversifying understory vegetation in southwestern ponderosa pine forests. Management practices of the last century have disrupted that ecological process and altered these forests to a point outside the historical range of variability. We measured the vegetation response to low and high severity fire, and post-fire seeding with Lolium perenne spp. multiflorum L. in the Warm Fire, which burned in 2006 in northern Arizona. L. perenne, an exotic, was seeded to control erosion and minimize the spread of exotics and is expected to exit the system 2-3 years post-seeding. We sampled within the burned area and along the fire perimeter in unburned sites to assess the fire and seeding effects on understory plant community composition, plant canopy cover, and species richness.

Results/Conclusions   Community composition was different in seeded and nonseeded plots with 15 indicator species in nonseeded and 6 indicators in seeded. Total plant cover was not different between seeded and nonseeded sites and the average cover of L. perenne was low (<5%) 1-year post-fire. The seeded species was still present in the system in 2009 (<2% cover) three years post-fire. There was no difference in exotic or native cover between seeded and non-seeded sites however, native bunch grass cover was significantly lower in seeded sites and may be due to increased competition from the seeded species. Our results indicate that the understory community is adapted to fire and plant response positive thus making it unnecessary to seed, especially with a non-native grass. We maintain the argument that fire, even high severity, can be beneficial to the understory plant community and forest integrity. On this particular fire, seeding was unnecessary and may have unintended long-term effects on the trajectory of the native plant community.