PARENT SESSION
Poster Session #59: Fire Ecology II.
Thursday, August 8. Presentation from 8:00 AM to 9:30 AM. Exhibit Hall B & C, TCC
131
Post-fire recovery in Sonoran desert ecosystems in relation to landform and depth to petrocalcic horizon.
Hubbert, Ken*,1, Narog, Marcia1, 1 Pacific Southwest Research Station, Riverside, CA
ABSTRACT- The expanding urban interface in the Sonoran Desert of Arizona has accelerated change in Sonoran plant communities by introducing human-caused wildfires; the frequency and size of which have increased dramatically. Under short fire intervals, saguaro (Carnegiea gigantea) can be eliminated. Over 30 percent of the saguaro-shrub has been burned during the last 3 decades. Water is an important limiting factor for post-fire recovery in landscapes underlain by petrocalcic layers (i.e. zones of secondary carbonate accumulation formed in surficial materials in warm, arid areas), which are impervious to roots and water flow. Soil water holding capacity of these desert soils is a function of depth to the petrocalcic horizon. Our objective was to determine how changes in soil depth to petrocalcic horizons affect soil water holding capacity in relation to simple slope landform positions, and whether this has an impact on the post-fire recovery of saguaro and associated species. Particle size distribution, bulk density, porosity, and soil water content were determined for the mineral soil in two different burn areas and an adjacent control. Ground penetrating radar was used to map the subsurface petrocalcic interface and to determine depth of soil to the petrocalcic horizon. We also evaluated cover and density of the six dominant plant species in relation to depth to petrocalcic horizon. Post-fire survival varied over the landscape and was positively correlated to soil water and depth to petrocalcic horizon. Post-fire recovery in this saguaro-shrub habitat relies on soil water capacity in relation to landform position and soil depth.
KEY WORDS: Carnegiea gigantea, wildfire, petrocalcic horizon, ground penetrating radar