2015 Winner: WATER RELATIONS AND PHOTOSYNTHESIS FOR ARTEMISIA TRIDENTATA ACROSS A GREAT BASIN DESERT-SIERRA NEVADA ELEVATION GRADIENT IN THE HISTORIC DROUGHT YEAR OF 2014

Project Information
WATER RELATIONS AND PHOTOSYNTHESIS FOR ARTEMISIA TRIDENTATA ACROSS A GREAT BASIN DESERT-SIERRA NEVADA ELEVATION GRADIENT IN THE HISTORIC DROUGHT YEAR OF 2014
Social Sciences
Environmental Studies
Understanding variation in water relations and photosynthesis for geographically widespread plant species that occur over environmental gradients may aid in understanding their responses to drought and future climate change. The evergreen shrub mountain big sagebrush (Artemisia tridentata ssp. vaseyana) is widespread throughout the Great Basin Desert and in the southwestern portion of its range, its upper elevational limit is at the ecotone with the Sierra Nevada tree-line. I evaluated the hypotheses that (1) photosynthesis and plant water potential will correspond to soil moisture and precipitation gradients, being lowest at the driest site, (2) experimental watering will rescue photosynthetic characteristics for plants at all sites, (3) germination success will differ for seeds collected from low vs. high elevation sites, and (4) germination will vary between three cool stratification treatments. To test these hypotheses I analyzed parameters determined from photosynthetic response curves to light (A-Q) and CO2 (A-Ci) pre- and post-watering, and through a common garden germination experiment. My results indicated that stomatal conductance (gs), maximum photosynthetic rate (Amax), maximum rate of carboxylation (Vcmax), maximum rate of electron transport (Jmax), dark respiration (Rdark), light compensation point (LCP), and quantum yield (Φ), all differ with elevation, but watering only increased gs, Jmax, and Amax at the lowest site. Germination was greater for seeds collected from the highest, wettest elevation, but did not differ between stratification treatments. These results indicate that both gs and Jmax may be limiting photosynthesis due to drought at the lowest elevation. Decreased carbon gain by these plants may result in lower contribution to community dynamics, higher fire risk, and greater feedback to atmospheric CO2.
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Students
  • Charlotte Chiara Reed (Eight)
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