Transgenerational effects of global environmental change: long-term CO2 and nitrogen treatments influence offspring growth response to elevated CO2

Global environmental changes can have immediate impacts on plant growth, physiology, and phenology. Long-term effects that are only observable after one or more generations are also likely to occur. These transgenerational effects can result either from maternal environmental effects or from evolutionary responses to novel selection pressures and are important because they may alter the ultimate ecological impact of the environmental change. Here, we show that transgenerational effects of atmospheric carbon dioxide (CO2) and soil nitrogen (N) treatments influence the magnitude of plant growth responses to elevated CO2 (eCO2). We collected seeds from Lupinus perennis, Poa pratensis, and Schizachyrium scoparium populations that had experienced five growing seasons of ambient CO2 (aCO2) or eCO2 treatments and ambient or increased N deposition and planted these seeds into aCO2 or eCO2 environments. We found that the offspring eCO2 treatments stimulated immediate increases in L. perennis and P. pratensis growth and that the maternal CO2 environment influenced the magnitude of this growth response for L. perennis: biomass responses of offspring from the eCO2 maternal treatments were only 54% that of the offspring from the aCO2 maternal treatments. Similar trends were observed for P. pratensis and S. scoparium. We detected some evidence that long-term N treatments also altered growth responses to eCO2; offspring reared from seed from maternal N-addition treatments tended to show greater positive growth responses to eCO2 than offspring from ambient N maternal treatments. However, the effects of long-term N treatments on offspring survival showed the opposite pattern. Combined, our results suggest that transgenerational effects of eCO2 and N-addition may influence the growth stimulation effects of eCO2, potentially altering the long-term impacts of eCO2 on plant populations.