WWETAC Projects

Project Title:Complex Restoration Challenges: Weeds, Seeds and Roads in a Forested Wildland Urban Interface

Principal Investigator: Becky K. Kerns, USDA Forest Service, Pacific Northwest Research Station, Corvallis, OR


Collaborators:Paul Doescher and Gabrielle Snider Forest Resources, Oregon State University

Key Issues/Problems Addressed:

Dry forests in the western U.S. are experiencing severe wildfires and a growing presence of invasive plant species. Policies strongly emphasize reducing hazardous fuels at the Wildland Urban Interface (WUI) where human communities and forests intersect. However, these areas present restoration challenges as they tend to have existing populations of exotic invasive species, frequent human disturbance, and the presence of roads. Understanding plant species seed banks is important in planning for desirable post-disturbance community conditions, developing integrated weed management programs, and for complying with State and Federal regulations.

Setting and Approach:

The study was conducted in eastern Washington mixed-aged dry-mixed conifer forest stands (Cle Elum Ranger District, Okanagan-Wenatchee National Forest). We characterized the aboveground vegetation and seed bank, and examined the patterns and relationships between vegetation and seed germinant abundance and richness in relation to seed bank layer source, distance to road, and herbicide treatment. 

Key Findings:

  • Most germinants (77%) and species (36 species) emerged from forest floor litter layers vs. mineral soil.
  • Overall germinant density, frequency, and richness were low regardless of distance to road, herbicide treatment, or seed bank layer.
  • Fourteen percent of germinants were exotic and invasive species, and were found in similar abundances regardless of proximity to road or herbicide treatment.
  • The herbicide treatment did not impact above ground vegetation or seed bank germinants.  
  • Little similarity was found between the largely mid- and late seral vegetation and early seral seed bank floras.   
  • Weed populations were largely confined to near road environments.


Some herbicide treatments may be ineffective and do not impact seed banks in the short term.  The seed bank contributions to post-disturbance understories may be relatively low, and consist largely of early seral species, especially if activities remove the litter layer.  While weed populations are largely confined to near road environments, the weed seed bank, is not.  Post disturbance studies are needed to fully evaluate the role of the seed bank in early secondary succession.

Master's Thesis and Published Abstracts

Snider, G. 2010. Aboveground vegetation and viable seed bank of a dry mixed-conifer forest at a wildland-urban interface in Washington State. Oregon State University Master's Thesis.

WWETAC Project ID: FY06BK7

Liberty Herbicide