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Harvard Forest REU Symposium Abstract 2012

  • Title: Examining the influence of ragweed regional ecotypes on reproductive investment and pollen output under increasing atmospheric CO2 concentrations
  • Author: Courtney C Maloney (University of California - Berkeley)
  • Abstract:

    Global temperatures and atmospheric concentrations of CO2 are predicted to rise throughout the next 100 years. These abiotic changes are likely to have profound changes on Earth’s vegetation. 10-20% of Americans suffer from ragweed-induced hay fever. Ragweed, (Ambrosia artemisiifolia) is a highly allergenic plant which grows throughout the United States, and is primarily concentrated in the Midwest and East. Ragweed pollen contains the protein Amb a 1; which is responsible for inducing an allergenic response in those sensitive to ragweed. We hypothesized that the predicted climate change conditions of elevated atmospheric CO2 will increase ragweed growth and pollen output. Different areas possess varying temperature and CO2 norms, leading to unique ecotypes in each region. Our aim is to understand how high atmospheric CO2 concentrations will affect ragweed growth among different ragweed ecotypes of the New England area. We subsampled 1/16 of a total of 1248 ragweed individuals drawn from 24 different populations from New York, Vermont, and Massachusetts at varying CO2 concentrations; 400 (ambient,) 600, and 800 ppm corresponding to present CO2 levels and those predicted for the next 100 years. We bagged the flowering spikes to capture pollen and harvested the spikes and the pollen after pollen release. After harvesting the spikes, we measured the length of spikes, determined the dry biomass of the spike, and quantified the amount of pollen from the different regional ecotypes in the three CO2 concentrations.



    We tested for differences in flower spike size and pollen production using ANOVA in which CO2 and ecotype were the main effects in the model. We also performed regressions to test for correlations between the continuous variables related to spike size and pollen output. In this preliminary analysis, ecotypes differed significantly in the length of the inflorescence. Inflorescence weight and pollen output per inflorescence were nearly significantly different between ecotypes. Initial analysis has suggested that there may be a relationship between inflorescence length and pollen output per inflorescence, as well as inflorescence weight and pollen output per inflorescence. These relationships can help develop estimators of pollen output, simplifying the data collection procedure for the larger experiment. Ragweed-induced hay fever poses major public health risks. Predicting how increased CO2 affects ragweed growth and pollen output and achieving greater understanding of how different local ecotypes respond to such changes, will better inform decisions regarding ragweed and allergenic plant policy and management.

  • Research Category: Ecological Informatics and Modelling

  • Figures:
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