Elevated CO2 and water addition enhance nitrogen turnover in grassland plants with implications for temporal stability

Authors: DIJKSTRA, FEIKE - University Of Sydney; CARRILLO, YOLANDA - Western Sydney University; Blumenthal, Dana; MUELLER, K - Cleveland State University; Lecain, Daniel; MORGAN, JACK - Retired ARS Employee; ZELIKOVA, T - University Of Wyoming; WILLIAMS, DAVID - University Of Wyoming; FOLLETT, R - Retired ARS Employee; PENDALL, ELISE - University Of Western Australia

Submitted to: Ecology Letters
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/8/2018
Publication Date: 3/5/2018
Citation: Dijkstra, F., Carrillo, Y., Blumenthal, D.M., Mueller, K.E., Lecain, D.R., Morgan, J., Zelikova, T.J., Williams, D., Follett, R.F., Pendall, E. 2018. Elevated CO2 and water addition enhance nitrogen turnover in grassland plants with implications for temporal stability. Ecology Letters. 21:674-682. doi:10.1111.ele.12935.
DOI: https://doi.org/10.1111.ele.12935

Interpretive Summary: In most terrestrial ecosystems, nitrogen (N) is scarce and therefore economical use of N by plants will affect their survival and reproduction. Plants continuously take up and lose N, but can reduce this N turnover by recycling N internally. Climate change has large impacts on N availability, but the impacts on plant N turnover are unknown. Here we show in a seven year long climate change experiment in a semiarid grassland that species with a high N turnover are less stable in time compared to species with a low N turnover. This suggests that species maintaining high temporal stability of biomass production can do so because they can count on greater internal N reserves at times when external N supply is low, while species with low temporal stability rely more on the fluctuating supply of external N from the soil. The N turnover of the whole plant community increased with elevated carbon dioxide and added precipitation, but was not affected by canopy warming. We demonstrate that an increase in asynchrony of species with different N turnover strongly contributed to the overall greater N turnover and temporal stability of the whole community. Therefore, variable N turnover among grassland plant species is important for stabilizing plant communities and maintaining forage production with climate change.

Technical Abstract: In most terrestrial ecosystems, nitrogen (N) is scarce and therefore economical use of N by plants will affect their fitness. Plants continuously take up and lose N, but can reduce this N turnover by recycling N internally through resorption and reallocation, which may be more economical when external N availability is low. Climate change has large impacts on N availability, but the impacts on plant N turnover and its role on plant community dynamics and structure are unknown. Here we show in a seven year long climate change experiment in a semiarid grassland that species with a high N turnover are less stable in time compared to species with a low N turnover. This suggests that species maintaining high temporal stability of biomass production can do so because they can count on greater internal N reserves at times when external N supply is low, while species with low temporal stability rely more on the fluctuating supply of external N from the soil. The N turnover of the whole plant community increased with elevated CO2 and added precipitation, but was not affected by canopy warming. Further, plant communities with higher N turnover showed greater temporal stability of biomass production. We demonstrate that an increase in asynchrony of species with different N turnover strongly contributed to the overall greater N turnover and temporal stability of the whole community. Therefore, variable N turnover among grassland plant species promoting temporal niche differentiation is important for stabilizing plant communities with climate change.