Nitrogen Fertilization Modified The Responses Of Schima Superba Seedlings To Elevated Co2 In Subtropical China

There are very few studies about the effects of relatively higher CO2 concentration (e.g., 1000 mu mol.mol(-1)) or plus N fertilization on woody plants. In this study, Schima superba seedings were exposed to ambient or eCO(2) (550, 750, and 1000 mu mol.mol(-1)) and N fertilization (0 and 10 g.m(-2).yr(-1), hereafter: low N, high N, respectively) for one growth season to explore the potential responses in a subtropical site with low soil N availability. N fertilization strongly increased leaf mass-based N by 118.38%, 116.68%, 106.78%, and 138.95%, respectively, in different CO2 treatments and decreased starch, with a half reduction in leaf C:N ratio. Leaf N was significantly decreased by eCO(2) in both low N and high N treatments, and N fertilization stimulated the decrease of leaf N and mitigated the increase of leaf C:N by eCO(2). In low N treatments, photosynthetic rate (Pn) was maximized at 733 mu mol.mol(-1) CO2 in August and September, while, in high N treatments, Pn was continuously increased with elevation of CO2. N fertilization significantly increased plant biomass especially at highly elevated CO2, although no response of biomass to eCO(2) alone. These findings indicated that N fertilization would modify the response of S. superba to eCO(2).