Post-fire succession of seeding treatments in relation to reference communities in the Great Basin

Questions Post-fire seeding has been widely implemented in the semiarid Great Basin because natural vegetation recovery may be compromised. Non-native species are often seeded to rapidly establish perennial cover and compete with invasive annuals. We asked whether seeding treatments with different amounts of native and non-native species followed different successional trajectories and whether they became more similar to reference communities over time. We considered restoration implications of seed mix choices and reference community options involving: (a) local unburned vegetation; and (b) reference states mapped by the USDA Natural Resources Conservation Service (NRCS) based on soil-vegetation associations. Location Tintic Valley, UT, USA. Methods Four post-fire seeding treatments differing by seed mix were installed alongside an unseeded control (USC) at two sites. Two seed mixes were comprised of native species and two were predominantly non-native. Vegetation was monitored 1-3 and 16-18 years after fire and seeding. Reference communities were characterized and compared using hierarchical clustering. Non-metric multidimensional scaling and permutation tests were used to determine successional trajectories of post-fire treatments in relation to reference communities. Results Local unburned reference communities had fewer herbaceous perennials and higher woody cover than NRCS reference communities, suggesting departure from conditions expected under minimal post-settlement disturbance. USCs became more similar to reference communities over time, though less so at a site with abundant invasive annuals. Trajectories of seeded treatments were driven by seed mix species, with native-only mixes approaching reference communities more closely than mixes with non-natives. Conclusions Gradual recovery of reference community composition is possible without seeding but the degree and rate of recovery can vary by site. Seeding can accelerate perennial vegetation recovery but may result in alternative successional trajectories, especially if non-native species are seeded. Carefully selected reference communities can serve as guides for formulating seed mixes when restoration of natural vegetation is desired.

Automated summary

Post-fire seeding is widely used in the semiarid Great Basin for vegetation recovery. This study compared the successional trajectories of different seeding treatments with native and non-native species and their similarity to reference communities, providing insights for post-fire restoration strategies.