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Effects of Nocturnal Warming on a Chinese Grassland Species
Li, Z., Lin, J., Zhang, T., Zhang, N., Mu, C. and Wang, J. 2014. Effects of summer nocturnal warming on biomass production of Leymus chinensis in the Songnen Grassland of China: From bud bank and photosynthetic compensation. Journal of Agronomy and Crop Science 200: 66-76.

The authors write that the warming that is being predicted for the future "is predicted to cause daily minimum air temperature to rise more rapidly than maximum air temperature, especially for mid to northern latitudes (IPCC, 2007; Lobell et al., 2007; Zhou et al., 2007)." And, in fact, over the course of the past century or so, daily minimum temperatures have indeed risen more rapidly than daily maximum temperatures, as conclusively demonstrated by Donat et al. (2013). So the question of the day is (if the earth ever begins to warm again): How will more rapidly rising nighttime (as opposed to daytime) temperatures impact plant growth and development?

What was done
In a study that broached this question, Li et al. wrote that "to understand how biomass production of the dominant grassland species Leymus chinensis responds to summer nocturnal warming in the eastern temperate Eurasian steppes, we simulated summer nocturnal warming (+4°C) using a phytotron system for 100 days operated based on the variation of diurnal temperatures over the past 12 years in the Songnen Grasslands."

What was learned
The six Chinese scientists report that "summer nocturnal warming significantly increased above-ground biomass production of parent and daughter shoots as well as increased below-ground root and rhizome biomass production," noting that "rhizome biomass increased faster than root biomass leading to an increase in the rhizome biomass to root biomass ratio." And they say that "nocturnal warming slightly increased the number of daughter shoots per plant, and significantly increased the number of buds in the below-ground bud bank and the number and length of rhizomes per plant."

What it means
In the concluding words of Li et al. in their paper's abstract, "these findings show that nocturnal warming in this ecosystem improves individual biomass accumulation due to photosynthetic compensation, and may enhance the population density and productivity of L. chinensis by increasing bud number in the below-ground bud bank during the early stage of ecological succession for grasslands dominated by L. chinensis."

Donat, M.G., Alexander, L.V., Yang, H., Durre, I., Vose, R., Dunn, R.J.H., Willett, K.M., Aguilar, E., Brunet, M., Caesar, J., Hewitson, B., Jack, C., Klein Tank, A.M.G., Kruger, A.C., Marengo, J., Peterson, T.C., Renom, M., Rojas, C.O., Rusticucci, M., Salinger, J., Elrayah, A.S., Sekele, S.S., Srivastava, A.K., Trewin, B., Villarroel, C., Vincent, L.A., Zhai, P., Zhang, X. and Kitching, S. 2013. Updated analyses of temperature and precipitation extreme indices since the beginning of the twentieth century: The HadEX2 dataset. Journal of Geophysical Research (Atmospheres) 118: 2098-2118.

IPCC. 2007. Fourth Assessment Report: Synthesis.

Lobell, D.B. 2007. Changes in diurnal temperature range and national cereal yields. Agricultural and Forest Meteorology 145: 229-238.

Zhou, L., Dickinson, R.E., Tian, Y., Vose, R.S. and Dai, Y. 2007. Impact of vegetation removal and soil aridation on diurnal temperature range in a semiarid region: application to the Sahel. Proceedings of the National Academy of Sciences USA 104: 17,937-17,942.

Reviewed 26 March 2014