Studying long-term, large-scale grassland restoration outcomes to improve seeding methods and reveal knowledge gaps

Authors: Rinella, Matthew - Matt; Espeland, Erin; MOFFATT, BRUCE - Bureau Of Land Management

Submitted to: Journal of Applied Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/24/2016
Publication Date: 8/1/2016
Publication URL: http://handle.nal.usda.gov/10113/5712980
Citation: Rinella, M.J., Espeland, E.K., Moffatt, B. 2016. Studying long-term, large-scale grassland restoration outcomes to improve seeding methods and reveal knowledge gaps. Journal of Applied Ecology. 53(5):1565-1574. doi:10.1111/1365-2664.12722.

Interpretive Summary: Considerable research is currently focused on restoring the World’s degraded grasslands by introducing species from seed. The research is continually providing valuable new insights into early seeded plant establishment, but more emphasis on longer, larger studies is needed to better quantify seeded plant performances across the broad temporal and spatial scales relevant to restoration managers. In this study, we investigated restoration outcomes at nine Great Plains coal mines to generate inferences reflecting relevant temporal and spatial scales without the huge expense of conducting manipulative experiments at these scales. The 327 fields of our study were subject to wide variation in management (e.g. seed rate, soil handling) and environmental (i.e. first growing season precipitation) predictors, and we quantified effects of these predictors on all plant groups (i.e. annual and perennial weeds; seeded grasses, forbs and shrubs). A small subset of seeded grasses proved capable of suppressing annual weeds. Regardless of seeding rate, first growing season precipitation and other factors determining starting densities, these grasses appeared similarly abundant long after seeding. Conversely, starting conditions regulated native shrubs: Though generally rare, shrubs were exceedingly rare where grasses were sown at high rates. Lowering grass rates would reduce costs, benefit shrubs and pose minimal risk of grass establishment failure. In fields where present, the exotic crested wheatgrass increased through time, so preventing this species from establishing is critical, especially around seeding time.

Technical Abstract: 1) Considerable research is currently focused on restoring the World’s degraded grasslands by introducing species from seed. The research is continually providing valuable new insights into early seeded plant establishment, but more emphasis on longer, larger studies is needed to better quantify seeded plant performances across the broad temporal and spatial scales relevant to restoration managers. 2) In this study, we investigated restoration outcomes at nine Great Plains coal mines to generate inferences reflecting relevant temporal and spatial scales without the huge expense of conducting manipulative experiments at these scales. The 327 fields (9±7 ha, 14±6 years post-seeding [mean±SD]) of our study were subject to wide variation in management (e.g. seed rate, soil handling) and environmental (i.e. first growing season precipitation) predictors, and we used compositional data analysis methods to quantified effects of these predictors on relative cover of all plant groups (i.e. annual and perennial weeds; seeded grasses, forbs and shrubs). 3) A small subset of seeded grasses proved capable of suppressing annual weeds. Regardless of seeding rate, first growing season precipitation and other factors determining starting densities, these grasses appeared similarly abundant long after seeding, suggesting convergence to constant final yield. Conversely, starting conditions regulated native shrubs: Though generally rare, shrubs were exceedingly rare where grasses were sown at high rates. Lowering grass rates would reduce costs, benefit shrubs and pose minimal risk of grass establishment failure. In fields where present, the exotic crested wheatgrass (Agropyron cristatum L.) increased through time, so preventing this species from establishing is critical, especially around seeding time. 4) These findings exemplify the practical knowledge that can emerge from studying restoration in practice. We discuss how integrating this method of study into an adaptive management framework would better fill knowledge gaps.