PARENT SESSION
Poster Session #31: Climate Change.
Wednesday, August 8, 2001. Presentation from 3:30 PM to 5:00 PM. Exhibition Hall

Effect of increased summer precipitation on high-temperature tolerance for Purshia tridentata.

ROYCE, GITANE¹, LOIK, MICHAEL¹, ¹

ABSTRACT- Current climate models predict increased precipitation for California by the year 2050. Our research focused on the impact of climate change on the widely-distributed shrub Purshia tridentata (Rosaceae) in eastern California. Three sites were chosen spanning a total of 1400 m elevation. We tested the hypotheses that (1) increased precipitation will enhance the tolerance of high temperatures, and (2) P. tridentata at low elevation are better able to survive high temperatures than at high elevation. In situ watering manipulations were used to determine the potential impact of increased precipitation on P. tridentata. Stress was assessed by measuring damage to cell and chloroplast membranes, as well as the ability to uptake CO₂. Canopy temperatures and ^stem indicate that plants at low elevation are more stressed by heat and drought compared to plants at high elevation. At 45°C CO₂ flux was -0.104 mol m^-2 s^-1 for plants at 1700 m and -3.056 mol m^-2 s^-1 for plants at 3100 m. Based on electrolyte leakage, LT₅₀ was 56°C at 1700 m, 54°C at 2600 m, and 49°C at 3100 m. Increased precipitation alleviated photosynthetic stress. These results indicate that plants at lower elevation sites are better able to withstand extreme high temperatures, and that increased precipitation will enhance the tolerance of high temperatures. Such effects may portend increased P. tridentata biomass at higher elevations of California in a future climate.

KEY WORDS: water potential, photosynthesis, Great Basin Desert, Sierra Nevada