Increased industrial capabilities and the use of fossil fuels in the Anthropocene has led to elevated atmospheric carbon dioxide (CO2), increased nitrogen deposition, more frequent biotic invasions, and declining species diversity. Considered in concert, these factors will likely significantly alter the timing of reproductive events (i.e. phenology) of plant species. Such phenological shifts could alter plant community composition and ecosystem function. However, current generalizations of plant functional group reproductive responses are only accurate in the short term and for individual variables. We assessed the independent and combined effects of CO2, N, and diversity treatments on the phenology and reproductive fitness of sixteen grassland plant species over a span of 17 years within an on-going CO2, N, and diversity experiment – BioCON in Minnesota, USA.
Results/Conclusions
We found that CO2 or N addition treatments alone impacted plant phenology, as has previously been demonstrated. These effects of CO2 and N differed among four plant functional groups (C4 graminoid, C3 graminoid, leguminous forb, non-leguminous forb). Additionally, we verified that the plants response to declining diversity is species specific. When combined, the CO2 and N addition treatments affected inflorescence number as well as the first day of flowering. Such interactive effects may result in altered timing of reproductive events, reduced species coexistence, shortened growing season length, and potentially reduced annual carbon uptake. Our results can inform future models of carbon uptake and climate change by explicitly examining the interactions between global change factors.