[Foliar water use efficiency and nitrogen use efficiency of dominant plant species in main forests along the North-South Transect of East China].

Based on the measurements of the foliar carbon content (Cmass, nitrogen content (Nmass), isotope abundance (delta13C and delta15N), and light response curve of 10 dominant plant species (Larix gmelinii, Quercus mongolica, Fraxinus mandshurica, Tilia amurensis, Acer mono, Pinus koraiensis, Cunninghamia lanceolata, Schima superba, Pinus massoniana, and Castanea henryi) in the main forests along the North-South Transect of Eastern China (NSTEC), this paper analyzed the differences and the relationships between the foliar water use efficiency and nitrogen use efficiency of the plant species. There existed significant differences in the foliar Nmass and delta15N among the plant species, manifesting as broadleaved species > coniferous species, and deciduous species > evergreen species. The maximum photosynthetic rate (Pn max) was coniferous species > broadleaved species, and deciduous species > evergreen species. Broadleaved and evergreen species tended to have higher foliar instantaneous water use efficiency (WUEi) and long-term water use efficiency (WUE), as compared to coniferous and deciduous species, but an opposite trend was observed in the foliar instantaneous nitrogen use efficiency (NUE) and long-term nitrogen use efficiency (NUE). Moreover, there was a significant difference in the foliar NUE between evergreen and deciduous species. No significant correlation was observed between WUEi and WUE, but a significant positive correlation existed between NUEi and NUE. There was a significant negative correlation between the foliar water use efficiency and nitrogen use efficiency at instantaneous or long-term time scales. In sum, the foliar water use efficiency and nitrogen use efficiency were dominated by plant life-form, and a trade-off existed between the two resources use efficiencies.