PARENT SESSION
Oral Session #22: Plant function and response to stress. Presiding: K. Miyanishi.
Tuesday, August 7, 2001. 8:00 AM to 11:45 AM. Hall of Ideas P&Q.
Comparative morphology, demography, and ecophysiology between two populations of Chrysothamnus viscidiflorus ssp. viscidiflorus at two different altitudes in the White Mountains, CA.
Kleier, Catherine1, Rundel, Philip1, 1
ABSTRACT- We investigated changes in morphology and water potential of Chrysothamnus viscidiflorus ssp. viscidiflorus[Asteraceae], a high altitude shrub, in response to temperature, precipitation, and wind differences associated with an altitudinal gradient in the White Mountains of California at the White Mountain Research Station between 3,000 and 4,000 m at 37o 33' N and 118o 15' W. Plants at both altitudes showed positive correlation of perimeter and height, but this correlation was stronger at the lower site (R2 = 0.595 at 3,100 m and R2 = 0.412 at 4,000 m). Plants at the highest altitude were shorter, but had greater surface area to volume ratios than plants at two lower altitudes as tested by ANOVA (F2, 2908 = 575.463, p < 0.001). Plants at the highest altitude also showed an increased percentage of flowering shoots than those at lower altitudes (F1, 1375 = 24.059). The average temperature over the growing season was 13.87 oC at 4,000 m and 15.31 oC at 3,100 m. Wind speeds were only slightly higher with increasing altitudes, though this varied greatly with day measured. Across all times and months, water potential for plants at the higher altitude site was higher (less negative) than for plants at the lower altitudes. Maximum photosynthesis rates averaged 16.5333 + 1.5343 
mol m-2 s-1 with temperature at 20 oC and light saturation at 2000 mol m-2 s-1. These studies indicate that water availability and temperature both play a role in structuring the morphology of this species in the White Mountains.
KEY WORDS: Altitudinal gradients, Alpine plants, Chrysothamnus viscidiflorus ssp. viscidiflorus, Plant morphology