PARENT SESSION
Poster Session 9: Arid Lands and Deserts
Tuesday, August 9, 5:00 PM - 6:30 PM, Exhibit Hall 220 A-E, Level 2, Palais des congrès de Montréal
Responding to temporal resource pulses in a spatially subsidized community: surprising strategies of desert annuals.
Wait, D. Alexander*,1, Anderson, Wendy2, 1 Missouri State University, Springfield, MO, USA2 Drury University, Springfield, MO, USA
ABSTRACT- The physiological responses of plants to resource pulses are well studied, while plant responses to resource pulses in spatially subsidized environments have received little attention. We examined the physiological responses of desert annuals to rain pulses and nutrient subsidies (in the form of seabird guano). Rain pulses occur every 2-7 years across the system (islands in the Gulf of California; precipitation range = 0-300mm; mean = 54 mm). Some communities are constantly subsidized with N and P while others are never subsidized. Subsidized communities have up to 20x higher soil N and P than unsubsidized communities. Mean annual productivity in unsubsidized communities in non-pulse years is 8 and in pulsed years is 55 g/m2; mean annual productivity in subsidized communities in non-pulsed years is 45 and in pulsed years is 225 g/m2. Contrary to expectations, subsidized plants had lower photosynthetic rates, higher water use efficiencies, and experienced greater water stress than unsubsidized plants in both pulsed and non-pulsed years. Greater productivity is achieved in subsidized communities by plants keeping stomatal conductance low, but increasing seasonal and daily carbon gain. Interestingly, this leads to an overall more conservative strategy for responding to pulses of rain over an entire growing season in subsidized than unsubsidized communities, but still allows plants in subsidized communities to respond rapidly to a simulated water pulse. For example, water potential and content of plants in subsidized communities is lower than in unsubsidized communities, but only plants in subsidized communities responded to an artificial water pulse. These data suggest ways in which plant strategies for responding to temporal pulses are modified by spatial subsidies; e.g., by modifying the typical pulse-reserve strategy that is favored by most desert annuals.
Key words: El Nino, plant gas exchange, island primary productivity, water use effeciency