PARENT SESSION
Oral Session # 56: Plant Ecology IV: Plant - Water Relations II.
Presiding: D Rosenthal
Wednesday, August 6. 1:30 PM to 5:00 PM, SITCC Meeting Room 200.
The effects of soil surface on community structure and plant function of Larrea tridentata in the Sonoran Desert.
Ignace, Danielle*,1, Huxman, Travis*,1, 1 University of Arizona, Tucson, AZ, USA
ABSTRACT- In the Sonoran Desert, strong plant community and geomorphic soil associations have been illustrated. We evaluated the ecophysiological patterns that underlie these plant and soil interactions by measuring various aspects of plant function seasonally for Larrea tridentata on previously characterized Pleistocene and Holocene surfaces at Tumamoc Hill, southern Arizona. The Holocene soil surface is characterized as sandy with no strong horizonal development, while the Pleistocene surface is a soil that effectively reduces rooting volume. Larrea on the Holocene have greater canopy volumes compared to Larrea on the Pleistocene soil surface. During the monsoon, Larrea on the Holocene had higher fluorescence, leaf nitrogen content and less negative predawn water potentials than the Pleistocene Larrea, but there were no differences in leaf photosynthesis and stomatal conductance. Following the monsoon, Larrea on the Pleistocene surface experienced greater water stress than the Holocene Larrea. Despite differences in water stress on the different soil surfaces, assimilation rates were statistically insignificant and slightly negative. There was greater mortality of Larrea during the dry 2002 growing season on the Pleistocene soil surface as compared to the Holocene site. The results may show how soil surface affects plant function and may shape community structure during episodic drought.
Key words: plant function, Sonoran Desert, Larrea tridentata, seasonal precipitation