Warming and elevated CO₂ affect the relationship between seed mass, germinability and seedling growth in Austrodanthonia caespitosa, a dominant Australian grass
HOVENDEN, MARK J. | WILLS, KAREN E. | CHAPLIN, REBECCA E. | VANDER SCHOOR, JACQUELINE K. | WILLIAMS, AMITY L. | OSANAI, YUI | NEWTON, PAUL C.D.
While the influence of elevated CO₂ on the production, mass and quality of plant seeds has been well studied, the effect of warming on these characters is largely unknown; and there is practically no information on possible interactions between warming and elevated CO₂, despite the importance of these characters in population maintenance and recovery. Here, we present the impacts of elevated CO₂ and warming, both in isolation and combination, on seed production, mass, quality, germination success and subsequent seedling growth of Austrodanthonia caespitosa, a dominant temperate C₃ grass from Australia, using seeds collected from the TasFACE experiment. Mean seed production and mass were not significantly affected by either elevated CO₂ or warming, but elevated CO₂ more than doubled the proportion of very light, inviable seeds (P < 0.05) and halved mean seed N concentration (P < 0.04) and N content (P < 0.03). The dependence of seed germination success on seed mass was affected by an elevated CO₂x warming interaction (P < 0.004), such that maternal exposure to elevated CO₂ or warming reduced germination if applied in isolation, but not when applied in combination. Maternal effects were retained when seedlings were grown in a common environment for 6 weeks, with seedlings descended from warmed plants 20% smaller (P < 0.008) with a higher root : shoot ratio (P < 0.001) than those from unwarmed plants. Given that both elevated CO₂ and warming reduced seed mass, quality, germinability or seedling growth, it is likely that global change will reduce population growth or distribution of this dominant species.
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