PARENT SESSION
Oral Session #53: Elevated CO₂: Communities, ecosystems, soils.
Presiding: G. Lin
Wednesday, August 7. 8:00 AM to 11:30 AM. Coconino Meeting Room, TCC.

Global change and plant communities: multiple resource gradients influence composition and productivity of an annual community.

WOLFE-BELLIN, KELLY^*,1, BAZZAZ, F.¹, ¹ Harvard University, Cambridge, MA

ABSTRACT- Impending global change within the next century is predicted to reduce biodiversity and may alter ecosystem function. The most striking and well-studied abiotic global change factors are atmospheric CO₂ concentration, air temperature, nitrogen deposition, and precipitation. We conducted a study in which a community of annual plants was exposed to multiple gradients of these four resources. Nine annual species were planted into experimental units that received a combination of the following four treatments: six levels of atmospheric CO₂, six levels of daytime air temperature, three nitrogen levels, and three water levels. A novel approach was employed, in which tunnels were used to create CO₂ and air temperature gradients. The CO₂ gradient ranged from ambient to 620 ppm and the temperature gradient ranged from ambient to 3.5°C above ambient. In the annual community, most responses were specific to species or functional groups (C3, C4 or legumes), but some treatment effects were apparent at the community level. As predicted, biomass and community composition responses to the CO₂ and temperature gradients were non-linear, and showed significant interactions with the nitrogen and water treatments. This research highlights the importance for scientists, when making predictions about ecosystem responses to future global climate change, to consider how plant communities respond to gradual changes in multiple abiotic resources.

KEY WORDS: CO₂, air temperature, plant community, annuals