ALBERT

Description: Aims We aimed to evaluate the changes in water-use efficiency (WUE) in native tree species in forests of subtropical China, and determine how coexisting species would be responding to increases in atmospheric carbon dioxide (CO 2 ) concentrations and nitrogen (N) deposition. Methods We used model forest ecosystems in open-top chambers to study the effects of elevated CO 2 ( ca . 700 µmol mol –1 ) alone and together with N addition (NH 4 NO 3 applied at 100kg N ha –1 year –1 ) on WUE of four native tree species ( Schima superba , Ormosia pinnata , Castanopsis hystrix and Acmena acuminatissima ) from 2006 to 2010. Important findings Our result indicated that all species increased their WUE when they were exposed to elevated CO 2 . Although higher WUE was shown in faster-growing species ( S. superba and O. pinnata ) than that of slower-growing species ( C. hystrix and Acmena acuminatissima ), the increased extent of WUE induced by elevated CO 2 was higher in the slower-growing species than that of the faster-growing species ( P 〈 0.01). The N treatment decreased WUE of S. superba, while the effects on other species were not significant. The interactions between elevated CO 2 and N addition increased intrinsic WUE of S. superba significantly ( P 〈 0.001), however, it did not affect WUE of the other tree species significantly. We conclude that the responses of native tree species to elevated CO 2 and N addition are different in subtropical China. The species-specific effects of elevated CO 2 and N addition on WUE would have important implications on species composition in China’s subtropics in response to global change.