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Seed Trait Responses of a Prairie Grassland to Warming and Elevated CO2

Paper Reviewed
Li, J., Ren, L., Bai, Y., Lecain, D., Blumenthal, D. and Morgan, J. 2018. Seed traits and germination of native grasses and invasive forbs are largely insensitive to parental temperature and CO2 concentration. Seed Science Research 28: 303-311.

Writing as background for their work, Li et al. (2018) say it is important to understand seed germination responses to climate change when predicting future changes in the composition, structure and function of ecosystems. And to thus address this topic, the six scientists utilized the Prairie Heating and CO2 Enrichment experiment at the U.S. Department of Agriculture's High Plains Grasslands Research Station in Cheyenne, Wyoming, USA, to investigate the effects of elevated CO2 and warming on various seed properties.

In doing so, Li et al. collected seeds over a six-year-period of two native (Bouteloua gracilis and Koeleria macrantha) and two invasive (Centaurea diffusa and Linaria dalmatica) species that had been growing at this site under ambient or elevated (600 ppm) atmospheric CO2 concentrations and ambient or elevated (+1.5°C warmer during the day and +3.0°C warmer at night) temperatures. The seeds obtained from the plants growing under these treatment conditions were then evaluated for mass and viability, as well as for fill and germination rates. And what did those evaluations reveal?

According to the authors, elevated CO2 and temperature, either alone or in combination, had no significant impact on seed fill, viability or mass, with the exception of one invasive species (C. diffusa), which experienced increased seed mass in the elevated warming treatment.

With respect to seed germination, one native species (B. gracilis) experienced increased germination rates in the combined elevated CO2 and elevated warming treatment. And although Li et al. say that "previous studies reported increased seed production [for the two invasive species] under future climate conditions, indicating that they could be more invasive at the regeneration stage in the future," they report that "final germination percentages of these [two] invasive species were not affected by treatments."

In light of their findings, the researchers conclude that "projected future temperature increases will have little effect on seed reproductive traits of native species." And as to the possibility that the two invasive species might gain ground on the natives, they add that their results "suggest that seed traits and germination play little role in this opportunism for these two grassland invaders."

Thus, based on the authors' findings reported above, it would appear that there will be little, if any, alteration in the composition of these Wyoming grasslands in response to rising atmospheric CO2 and temperatures in the future.

Posted 20 March 2019