Location: Adaptive Cropping Systems LaboratoryTitle: Could recent increases in atmospheric CO2 have acted as a selection factor in wild oat populations? Implications for cultivated and wild oat competition
Submitted to: Weed Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/9/2017
Publication Date: 12/1/2017
Citation: Ziska, L.H. 2017. Could recent increases in atmospheric CO2 have acted as a selection factor in wild oat populations? Implications for cultivated and wild oat competition. Weed Research. 57:399-405.
Interpretive Summary: Carbon dioxide, CO2, in addition to water, sunlight and nutrients is a resource plants need in order to grow. As CO2 increases, it will therefore stimulate the growth of plants. But as a resource increases, different plant species will respond differently. This differential response is likely to lead to changes in plant competition. Plant competition in turn, is especially important in agriculture as weeds can compete with crops for necessary resources. To determine if the recent increase in CO2 may have already resulted in changes in crop:weed competition, we compared the result of wild oat, a known weed of cereal crops, collected at the same location but at two different times, once in 1967 when atmospheric CO2 was 320 ppm (parts per million) and again in 2014 when CO2 was 403 ppm. Our results indicate that the newer wild oat population appears to have adapted, or evolved to take advantage of the recent increase in atmospheric CO2. In contrast, cultivated oat, when grown competitively with both the old (1967) and new (2014) wild oat, showed decreased competitive ability. While additional information on the generality of the crop:weed is needed, these data indicate that weeds may be adapting more rapidly to rising levels of atmospheric carbon dioxide; and, consequently, may be harder to manage as atmospheric CO2 increases.
Technical Abstract: Projected increases in atmospheric carbon dioxide concentration, [CO2] may lead to differential selection and competition between weeds and crops. Yet, the current level of atmospheric [CO2] already reflects a rapid rise (~25%) from mid-20th century levels. To assess whether this increase could have already resulted in differential selection between weeds and crops, two temporally distinct populations of wild oat (WO) (Avena fatua) from the same geographic location, one from the 1960s (WOold); and one from 2014 (WOnew) were grown with and without a cultivated oat (CO) line, Clintland 64 (Avena sativa) at their [CO2] collection values (ca 315 and 418 µmol mol-1, respectively). Monocultures of each WO population differed in their response to recent increases in atmospheric [CO2], with WOnew showing a significantly higher response for all vegetative parameters relative to WOold. Assessment of competitive outcomes indicated that at 315 µmol mol-1; CO was at a competitive advantage relative to either WO population for leaf area and total above ground biomass. However at current levels of CO2, an overall increase in WOnew competitive ability was observed relative to the CO line. Overall, these differences are consistent, but not conclusive, of improved evolutionary fitness and increased early competitive ability of WO relative to CO as a function of the recent increase in atmospheric [CO2]. While additional empirical studies are needed, these preliminary results indicate that weeds, may be adapting more rapidly to rising levels of atmospheric carbon dioxide.