Biogeosciences www.biogeosciences.net 1726-4170 1726-4189 9 1 2012 10.5194/bg-9-375-2012 http://www.biogeosciences.net/9/375/2012/ http://www.biogeosciences.net/9/375/2012/bg-9-375-2012.html http://www.biogeosciences.net/9/375/2012/bg-9-375-2012.pdf 375 384 2012-01-18 Day and night warming have different effect on root lifespan W. M. Bai J. Y. Xia S. Q. Wan W. H. Zhang L. H. Li llinghao@ibcas.ac.cn State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, the Chinese Academy of Sciences, Beijing 100093, China Roots are key components of C cycling in terrestrial ecosystems and play an important role in the regulation of response of terrestrial ecosystems to global climate warming, which is predicted to occur with greater warming magnitudes at night than during daytime across different regions on the Earth. However, there has been no detailed study to investigate the effect of asymmetrical warming on root dynamics at the level of terrestrial ecosystems. To understand the effects of day and night warming on root lifespan in the semiarid temperate steppe in northern China, a field study with a full factorial design including control, day warming, night warming and continuous warming was conducted using modified rhizotron technique during three growing seasons in 2007–2009. Our results show that day, night and continuous warming had different effects on longevity of roots born in spring, summer and autumn, and that day warming significantly prolonged overall lifespan for the roots born in the three growing seasons, while night warning had no effect on overall lifespan. Day and night warming had different effects on root non-structural carbohydrate content, suggesting that allocation of photoassimilate may account for the differential responses of root lifespan to day and night warming. 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