PARENT SESSION
Tuesday, August 8, 5:00-6:30 pm
Poster Session 9 - Restoration and conservation ecology and ecosystem management
Exhibit Hall, Ballroom Level, Cook Convention Center

Historical land use affects post-fire vegetation development.

Narog, Marcia^*,1, ¹ USDA Forest Service, Riverside, CA, USA

ABSTRACT- Vegetation in nine small watersheds with different resource management and fire histories was compared on the San Dimas Experimental Forest, California after the 2002 Williams Fire. All watersheds were originally vegetated with mixed chaparral and all burned in wildfires in 1938, 1960, and 2002. After 1960, three watersheds were seeded with grass and treated with herbicide; three others were allowed to naturally regenerate, and two watersheds (one each chaparral and grass conversion) contained narrow black lines (areas prescribed burned in 1999)hence creating another vegetation age class. Vegetation composition and structure in each watershed was measured annually beginning in 2003. Vegetation sampling evaluated post-fire ground cover, pre-fire shrub density, post-fire sprouting shrub density, and post-fire shrub seedling density. Each watershed had thirty 10 m line transects, thirty 10 m belt transects, and thirty 1 m2 plots. Recovery of the nineteen species of shrubs and bushes differed among treatments. Herbicide treated watersheds averaged fewer species than untreated, and the 1999 fire treatment showed an intermediate response. This was true for all physiognomic groups: tree, shrub, bush (sub-shrub), and herbaceous. Shrub cover was less on treated compared to untreated plots. Seedling germination of shrub species was observed the first year after fire, but seedling success was low overall due to drought. Increased disturbance caused by land management practices and fire history reduced long-term plant species diversity, establishment and development.

Key words: resource management, chaparral, fire