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Vegetation succession in post-fire seeding treatments - Final Report to the Joint Fire Science Program

Author(s): Francis F. Kilkenny, Jeffrey E. Ott, Daniel D. Summers, Tyler W. Thompson
Year Published: 2018

Seed mixes used for post-fire seeding in the Great Basin are often selected based on short-term rehabilitation objectives, such as ability to rapidly establish and suppress invasive exotic annuals that drive altered fire-regimes via fine build-up (e.g. cheatgrass, Bromus tectorum L.), but longer-term considerations are also important, including whether seeded plants persist, continue to suppress invasive weeds, and promote recovery of desired vegetation states. To better understand long-term effects of post-fire seed mixes, we revisited study sites in Tintic Valley, Utah, where seeding experiments had been initiated following a 1999 wildfire. Four different mixes, including two comprised entirely of native species, had been applied using rangeland drills at a shrubland site and aerial seeding followed by chaining at a woodland site. New vegetation data collected in 2015 through 2017 (16+ years post-fire) revealed changes relative to data collected in 2000 through 2002. We found significant increases in total cover of seed-mix species in all treatments, including the unseeded control where these species were present as residual populations or had spread from seeded treatments. Some seeded species, particularly rhizomatous grasses, increased while others declined. Native perennials that were not part of seed mixes had higher recruitment in unseeded treatments and were especially prominent at the higher-elevation aerial seeding site. Exotic annual forb cover decreased in all treatments while cheatgrass increased in some treatments, especially the unseeded control and to a lesser extent native-only seeded treatments. Successional trajectories in community composition differed significantly between seed-mixes that included introduced species and the native-only mixes, which moved toward reference states in unburned areas while the introduced mixes did not. Results indicate that post-fire seeding has lasting effects on vegetation composition and structure, implying that seed mixes should be carefully formulated to promote long-term management objectives. Seed mixes containing competitive introduced species may be especially effective for long-term cheatgrass suppression, but native-only mixes can also serve this purpose while avoiding drawbacks of non-native species introductions, including the altered successional trajectories that move plant communities into novel states that may not support important wildlife habitat. Where recovery of natural vegetation or wildlife habitat is desired, post-fire seeding may not always be needed or may be best accomplished by seeding native species.

Citation: Kilkenny, Francis; Ott, Jeffrey E.; Summers, Daniel D.; Thompson, Tyler W. 2018. Vegetation succession in post-fire seeding treatments - Final Report to the Joint Fire Science Program. JFSP Project No. 15-1-07-39. Boise, ID: US Forest Service, Rocky Mountain Research Station. 26 p.
Topic(s): Fire Ecology, Fire Effects, Post-fire Management, Post-fire Rehabilitation, Seeding, Recovery after fire, Restoration
Ecosystem(s): None
Document Type: Technical Report or White Paper
NRFSN number: 18258
FRAMES RCS number: 56790
Record updated: Nov 5, 2018