| Global change may impact terrestrial ecosystems through effects on the regenerative capacities of plants. Changes in energy allocation to reproduction, as a result of increasing CO2, changing temperature or precipitation, could shift the ecological and evolutionary factors that control plant distributions and species interactions. These changes in energy allocation to reproduction are manifested as seed number, viability and mass change. We conducted a meta-analysis of results from a number of different elevated CO2 experiments with the goal of determining patterns of reproductive response across a large number of species and functional types. In addition, we performed a number of experimental studies that evaluated the patterns of allocation to reproduction in the context of adult performance and offspring consequences. The relative biomass allocation to reproduction is not consistently affected by exposure to elevated CO2. Accordingly, total seed production generally increases, while seed mass decreases upon exposure to elevated CO2, but the response is dependent upon plant functional type. Nitrogen-fixing plants do not exhibit reduced seed mass at elevated CO2, but may actually show enhancement. Changes in seed characteristics based on functional type suggest that the nitrogen economy of plants at elevated CO2 is very important in combination with alterations of allometric relationships, such that both result in potential life history consequences. CO2-affected changes in reproductive characters may have important implications for species distributions and trophic interactions in natural and agricultural ecosystems. |
