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How are the rates and resource costs of plant reproduction affected by global warming?
Lambrecht, Susan*,1, 4, Loik, Michael1, 4, Inouye, David2, 4, Harte, John3, 4, 1 University of California, Santa Cruz, CA4 Rocky Mountain BIological Laboratory, Gothic, CO2 University of Maryland, College Park, MD3 University of California, Berkeley, CA
ABSTRACT- Under predicted patterns of climate change, the distribution of plant species is expected to shift. The capacity to reproduce is one factor contributing to the potential of a species to persist within its current range or to disperse to new ranges as climate changes. To address how plant reproduction may be influenced by global warming, we have used an ongoing experiment in a Colorado subalpine meadow that employs infrared warming to simulate future radiative forcing near the soil surface. We tested the hypothesis that allocation of resources to reproduction may be partially explained by responses to earlier snowmelt in the spring, which leads to increased exposure to episodic freezing events, and decreased soil moisture in the summer. For two species that exhibit reduced rates of reproduction, the niveal emergent Erythronium grandiflorum, and summer-flowering Delphinium nuttallianum, we measured the water costs of reproduction as well as foliar gas exchange rates and properties. For D. nuttallianum, floral transpiration rates were greater in the warmed plots than in the control plots. Furthermore, leaf water potential, photosynthesis, and stomatal conductance were significantly lower in the heated plots as compared to the control plots. However, warming did not produce similar effects for E. grandiflorum, for which increased exposure to spring freezing events damages the reproductive structures, precluding subsequent flower and fruit production. Understanding the mechanisms that reduce reproduction for these species while producing no response in others exposed to the warming experiment is critical for discerning how the abundance and distribution of species will be altered by climate change.
Key words: climate change, water-use efficiency, reproductive allocation, subalpine