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

Authors: WILDER, LACEY - Utah State University; VEBLEN, KARI - Utah State University; GUNNELL, KEVIN - Utah Division Of Wildlife Resources; Monaco, Thomas

Submitted to: Restoration Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/23/2019
Publication Date: 11/1/2019
Citation: Wilder, L.E., Veblen, K.E., Gunnell, K.L., Monaco, T.A. 2019. Influence of fire and mechanical sagebrush reduction treatments on restoration seedings in Utah, United States. Restoration Ecology. 27(2):308=319. https://doi.org/10.1111/rec.12860.
DOI: https://doi.org/10.1111/rec.12860

Interpretive Summary: Practitioners must consider seedbed conditions, and species requirements when planning restoration seedings to accommodate differences in disturbance intensity and sowing depth created by treatments. A prior knowledge of the resilience potential of restoration sites, species nativity, and species performance should be used to formulate seeding mixes that minimize rapid increases in one species from interfering with other species in the mixture when species diversity is a management goal. Variation in restoration outcomes among plant community types indicates that lower elevation, warm/dry temperature/moisture sites stand to gain the most from shrub treatment and seedling efforts. While increases in seeded grasses were observed for all treatment types, relatively low performance of forbs exposes a fundamental shortfall for restoration practitioners in this ecosystem.

Technical Abstract: 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 seedling 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 influeced 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 increasdes of non-native relative to native seeded species will influence species diversity and successional trajectories of restoration sites.