Wednesday, November 15, 2006

Vegetation Changes across Distinct Parent Materials 15 Years after the Dude Fire.

Jackson Leonard1, Alvin L. Medina1, Daniel Neary1, Aregai Tecle2, and Jonathan W. Long1. (1) USDA Forest Service, Rocky Mountain Research Station, 2500 S Pine Knoll Dr, Flagstaff, AZ 86001, (2) Northern Arizona Univ, 2500 S Pine Knoll Dr, Flagstaff, AZ 86001

Recent studies of forest vegetation in the Mogollon Rim area have found that severe crown fires have induced shifts in vegetation from ponderosa pine forests to manzanita-oak shrublands.  Differences in parent materials could potentially alter the responses of different areas subjected to severe wildfire.  To test this hypothesis, vegetation and ground cover in burned and unburned areas were compared across sandstone and limestone parent materials. The study sites are located in pine/juniper/oak forest below the Mogollon Rim on the Tonto National Forest in central Arizona.  The burned sites had been burned by the Dude wildfire in 1990.  Half the sites were sampled in 2001 and 2002, and the other half in 2005.  Woody stem density (stems/ha) was measured in 10 macro-plots (5 x 8 m) at each site.  Sixty sites were evenly distributed across sandstone/limestone parent materials and burned/unburned areas.  All comparisons used a 95% confidence interval with an n = 15.  Ponderosa pine (Pinus ponderosa) density was greater on sites of limestone influence within the burned area than on sandstone sites.  Manzanita (Arctostaphylos spp.) density was higher on the burned sandstone sites  than on the burned limestone sites.  Although, no correlation with soil organic matter and macronutrients was observed, the results suggest parent materials can influence vegetative response to severe wildfire and should be a consideration of post-fire management strategies.