CAREER: Plant Evolution at Low CO2: Responses of Ice Age Trees

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Atmospheric carbon dioxide is the main source of carbon for living organisms and is a critical substrate for plant photosynthesis. This research seeks to determine how plants evolved in response to low carbon dioxide concentrations that occurred during the last ice age (18,000-20,000 years ago). During that period, carbon dioxide concentrations were approximately half of the current value, and these low levels greatly reduce the growth of modern plants. In order to understand how plants evolved in response to low carbon dioxide in the past, the proposed research uses plant specimens from two remarkable collections dating to the last ice age: juniper trees preserved within the La Brea tar pits in southern California and kauri trees preserved within bogs on the North Island, New Zealand. These specimens allow for comparisons between ice age and modern trees for assessing the effects of low carbon dioxide on plant physiology, growth, and evolution. Plant responses to changing carbon dioxide will be measured with annual resolution using carbon isotope analysis of tree rings, along with measurements of leaf morphology and seed size. Broader impacts for this CAREER project will involve the establishment of a SEEDS (Strategies for Ecology Education, Development and Sustainability) chapter at the University of Kansas that will strive to increase the number of students from under-represented groups that enter the field of ecology. This chapter will involve mentoring of undergraduates, student travel to national meetings, and a speaker series with minority scientists. From this research, a more accurate understanding of plant responses to past global changes will be acquired, and from this, insights will be gained into the evolutionary responses of plants to increasing carbon dioxide concentrations that are predicted for the near future.