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Influence of fire and mechanical sagebrush reduction treatments on restoration seedings in Utah, United States

Wilder, Lacey E., Veblen, Kari E., Gunnell, Kevin L., Monaco, Thomas A.
Restoration ecology 2019 v.27 no.2 pp. 308-319
Artemisia, altitude, ecosystem services, ecosystems, forbs, grasses, indigenous species, introduced species, mechanical methods, meta-analysis, mortality, perennials, planning, seedbeds, shrubs, sowing, species diversity, understory, vegetation, woody plants, Utah
Overabundance of woody plants in semiarid ecosystems can degrade understory herbaceous vegetation and often requires shrub reduction and seeding to recover ecosystem services. We used meta‐analysis techniques to assess the effects of fire and mechanical shrub reduction over two post‐treatment timeframes (1–4 and 5–10 years) on changes in cover and frequency of 15 seeded species at 63 restoration sites with high potential for recovery. Compared to mechanical treatments, fire resulted in greater increases in seeded species. Native shrubs did not increase, and forbs generally declined over time; however, large increases in perennial grasses were observed, suggesting that seeding efforts contributed to enhanced understory herbaceous conditions. We found greater increases in a few non‐native species than native species across all treatments, suggesting the possibility that interference among seeded species may have influenced results of this regional assessment. Differences among treatments and species were likely driven by seedbed conditions, which should be carefully considered in restoration planning. Site characteristics also dictated seeded species responses: while forbs showed greater increases in cover over the long term at higher elevation sites considered to be more resilient to disturbance, surprisingly, shrubs and grasses had greater increases in cover and frequency at lower elevation sites where resilience is typically much lower. Further research is needed to understand the causes of forb mortality over time, and to decipher how greater increases of non‐native relative to native seeded species will influence species diversity and successional trajectories of restoration sites.