Postwildfire seeding to restore native vegetation and limit exotic annuals: an evaluation in juniper‐dominated sagebrush steppe

Abstract

Reestablishment of perennial vegetation is often needed after wildfires to limit exotic species and restore ecosystem services. However, there is a growing body of evidence that questions if seeding after wildfires increases perennial vegetation and reduces exotic plants. The concern that seeding may not meet restoration goals is even more prevalent when native perennial vegetation is seeded after fire. We evaluated vegetation cover and density responses to broadcast seeding native perennial grasses and mountain big sagebrush (Artemisia tridentata Nutt. spp. vaseyana [Rydb.] Beetle) after wildfires in the western United States in six juniper (Juniperus occidentalis ssp. occidentalis Hook)‐dominated mountain big sagebrush communities for 3 years postfire. Seeding native perennial species compared to not seeding increased perennial grass and sagebrush cover and density. Perennial grass cover was 4.3 times greater in seeded compared to nonseeded areas. Sagebrush cover averaged 24 and less than 0.1% in seeded and nonseeded areas at the conclusion of the study, respectively. Seeding perennial species reduced exotic annual grass and annual forb cover and density. Exotic annual grass cover was 8.6 times greater in nonseeded compared to seeded areas 3 years postfire. Exotic annual grass cover increased over time in nonseeded areas but decreased in seeded areas by the third‐year postfire. Seeded areas were perennial‐dominated and nonseeded areas were annual‐dominated at the end of the study. Establishing perennial vegetation may be critical after wildfires in juniper‐dominated sagebrush steppe to prevent the development of annual‐dominated communities. Postwildfire seeding increased perennial vegetation and reduced exotic plants and justifies its use.

Long‐term evidence for fire as an ecohydrologic threshold‐reversal mechanism on woodland‐encroached sagebrush shrublands

“…First, our study does not define a timeline for reversal of a soil erosion feedback or the shift to "resource-conserving" conditions in these systems. Re-establishment of sagebrush steppe vegetation and associated surface soil conditions on degraded woodlands is highly variable, is driven by conditions at the time of treatment, the type of treatment, and posttreatment weather, and may require seeding Bates et al, 2014;Bates et al, 2017;Bates & Davies, 2016;Chambers et al, 2014;Davies et al, 2019;Miller et al, 2005;Miller et al, 2013;Miller et al, 2014;. However, our study does demonstrate tree removal on late-succession woodlands can effectively re-establish a "resource-conserving" vegetation structure and reverse the soil erosion feedback.…”

“…Re-establishment of sagebrush steppe vegetation and associated surface soil conditions on degraded woodlands is highly variable, is driven by conditions at the time of treatment, the type of treatment, and posttreatment weather, and may require seeding Bates et al, 2014;Bates et al, 2017;Bates & Davies, 2016;Chambers et al, 2014;Davies et al, 2019;Miller et al, 2005;Miller et al, 2013;Miller et al, 2014;. Re-establishment of sagebrush steppe vegetation and associated surface soil conditions on degraded woodlands is highly variable, is driven by conditions at the time of treatment, the type of treatment, and posttreatment weather, and may require seeding Bates et al, 2014;Bates et al, 2017;Bates & Davies, 2016;Chambers et al, 2014;Davies et al, 2019;Miller et al, 2005;Miller et al, 2013;Miller et al, 2014;.…”

“…Cover of sagebrush, native grasses, and forbs and respective seed sources are often insufficient in Phase III for re-establishing these vegetation covers simply through tree removal (Bates et al, 2014;Davies, Bates, & Boyd, 2019). Thus, sites in Phase III are particularly susceptible to long-term degradation following wildfire that removes limited existing cover and exacerbates and perpetuates high run-off and erosion rates (Davies et al, 2019;Miller, Chambers, Pyke, Pierson, & Williams, 2013;Pierson et al, 2011;Williams, Pierson, Robichaud, & Boll, 2014).…”

To burn or not to burn: Comparing reintroducing fire with cutting an encroaching conifer for conservation of an imperiled shrub‐steppe

“…Based on the treatment‐dependent rate of post‐treatment juniper development, a conservative estimate of the difference between cut and burned areas suggests that sagebrush will dominate/codominate the overstory 44% longer on burned areas (Figure ). Mountain big sagebrush cover, in general, can be rapidly recovered after fire in western juniper‐encroached shrub‐steppe with seeding sagebrush (Davies & Bates, ; Davies, Bates, & Boyd, ; Davies, Bates, Madsen, & Nafus, ). With successful seeding, sagebrush dominance can be extended to the majority of the time interval that juniper is controlled in burned areas.…”

“…A concern with woody plant treatments, including juniper removal in sagebrush ecosystems, is their potential to cause undesirable shifts in the plant community, in particular increased exotic plants (Archer et al, ; Bates, Sharp, & Davies, ; Bates, Svejcar, Miller, & Davies, ; Davies et al, ; Roundy, Miller, et al, ). Exotic annual grass increases, however, are generally assumed to be more problematic with burning, likely because of the positive feedback cycle between exotic annual grasses and fire (Chambers et al, ; D'Antonio & Vitousek, ; Rossiter, Setterfield, Douglas, & Hutley, ).…”