Welcome! This site highlights research findings from Joint Fire Science Program (JFSP) sponsored projects that focused on developing a better understanding of the basic ecology and disturbance history of southwestern Oregon’s oak woodland and chaparral plant communities, and assessing responses of these communities to fuel reduction thinning treatments. These plant communities, which are among the least understood in the Pacific Northwest, were also classified and mapped as a part of this project.  Findings summarized here advance both basic understanding of these ecosystems, and provide valuable information to the land managers that oversee them.

Personnel from the Medford, OR office of the Bureau of Land Management (BLM), Oregon State University (OSU), and Southern Oregon University (SOU) gathered and analyzed data largely from oak woodlands and chaparral in the Applegate Valley to answer the following:

SW Oregon interior valley landscape

Research Questions

  • What plant communities comprise the nonconiferous component of vegetation in the area, and how does their occurrence relate to site conditions and disturbance history?

  • What is the current stand structure, age structure, and regeneration status of Oregon white oak communities? How have structures changed over time?
  • What age structures currently characterize southwest Oregon chaparral?  Does it appear that chaparral been influenced by past fire disturbances and current fire suppression, and, if so, in what ways? Do fuels treatments reproduce structures observed in undisturbed chaparral or mimic the function of fire disturbance?
  • What are the consequences of fuel reduction treatments for native plant communities or native plant species of concern?

  • What is the relationship of fuel reduction treatment to invasion by exotic plants?

  • Is seeding of prescribed-burned sites with native grasses effective at encouraging their establishment or inhibiting invasion by exotic species?

  • Do wildfires behave differently in areas that have been thinned compared to unthinned but otherwise similar areas?  
Old-growth whiteleaf manzanita

This study assessed the relationships of environmental and disturbance variables to current vegetation composition in grassland, shrubland, and woodland vegetation types. Field surveys were used to define and map 13 plant assemblages. GIS was used to investigate patterns of assemblage occurrence on the landscape in relation to site conditions and disturbance history. This benchmark assessment provides detailed vegetation maps and baseline data important for monitoring change over time, and aids in understanding and conservation of unique vegetation types. Go to report.

GIS image near Ruch, OR, of non-coniferous vegetation associations characterized and mapped on BLM lands by E. Pfaff.

 

How do fuel reduction treatments affect understory plant communities and site conditions? Do treatments favor native species or foster expansion or invasion of exotics? Do different plant trait groups respond differently to treatment? Do effects differ between treatment types (hand-cut and pile-burn versus mechanical mastication)? To answer these questions, vegetation and abiotic characteristics were measured along paired transects in thinned and unthinned chaparral and oak-shrub communities. The central goal of this study was to provide information on responses of these communities to fuel reduction treatments to assist land managers who want to design treatments that achieve fuel-reduction or restoration goals without exacerbating problems with invasive species. Go to report or see a JFSP Fire Science Brief.

Aerial photo of thinned landscape

The Buncom Bowl fuel-reduction project in the Applegate Valley of Southwest Oregon was burned by the Squires fire (2002) before project completion. Prior plant community mapping, permanent transects, and established photo-points together with post-fire surveys provided an opportunity to view fire interaction with treated and untreated woodland and chaparral stands.  Post-fire site and vegetative conditions were compared among handcut-piled-and-burned (HPB), handcut-and-piled only (HP), mechanically masticated (SB), and untreated sites. How is post-fire vegetation survival and structure different between treatments? How does wildfire interact with fuel manipulations to affect soil and seedbanks and determine future vegetation? Go to report.

Oaks burned by the Squires wildfire
Aerial map with vegetation associations overlay
Research Projects in Brief

An interior valley of Southwest Oregon. Photo K. Sikes.

Old-growth whiteleaf manzanita. Photo D. Coen.

Page by Olivia Duren. Updated 4/2010.

 

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Aerial photgraph of vegetation after fuels reduction in the Applegate Adaptive Management Area. Photo courtesy of the BLM.
Oaks burned by the 2002 Squires Fire. Photo P. Hosten.

Large acreages of Oregon white oak (Quercus garryana) communities in southwestern Oregon are thinned to reduce fire hazard and accomplish ecosystem restoration under the assumption that current fuel loads are unnaturally high and stands are unnaturally dense as a result of fire suppression.  Although oak communities are a characteristic landscape component in this region, little is known about their current or historic stand structures.  What stand structures characterize southwest Oregon white oak woodlands, and do these appear to vary along environmental or disturbance history gradients? How do structures of southwestern Oregon woodlands compare to those of Oregon white oak woodlands elsewhere? Are these woodlands plagued by the regeneration problems that occur in other parts of this species’ range? When did these woodlands originate --before European settlement, before the onset of effective fire suppression, or more recently? We inventoried stand structure and age structure, tree health, and oak regeneration to advance basic understanding of these systems, and to foster ecologically-based management within them. Go to report. 

Fuels treatments in chaparral shrublands on BLM lands in southwest Oregon aim to mitigate presumed ecosystem degradation and increased fire hazard thought to be caused by fire suppression. The fire ecology of this ecosystem is virtually unknown, however.  What age structures and fire regimes characterize southwest Oregon chaparral, and does it appear that these structures have been altered by fire suppression?  Are current fuels treatments likely to accomplish restoration of these systems?  To what extent are community processes in southwest Oregon chaparral, which represents the northernmost extent of the chaparral range, comparable to California chaparral and other Mediterranean-climate obligate-seeder shrub communities?   To address these questions, we studied patterns in age structure of two obligate-seeding chaparral shrubs, sticky whiteleaf manzanita (Arctostaphylos viscida) and buckbrush (wedgeleaf) ceanothus (Ceanothus cuneatus), and assessed relationships of these structures to environment and fire.  Go to report. 

Ridetop chaparral in southwest Oregon
Buckbrush chaparral often dominates ridgetops in SW Oregon interior valleys. Photo O. Duren
Thinned oak woodland in the Wildland Urban Interface
This oak woodland in the Wildland Urban Interface was thinned to a savannah-like spacing. Photo L. Gilligan.