Abstract: Global warming and nitrogen deposition are two main global change drivers, often occurring simultaneously. However, most of related studies referred to only single factor. The concentrations of carbon (C), nitrogen (N) and phosphorus (P) in fine roots affect forest ecosystem productivity and C storage. The effects of climate warming and N deposition on fine root chemical components remain unclear. We conducted a two-factor experiment of warming (W, +4 ℃) and N addition (N, +40 kg N·hm^-2·a^-1) at the Forest Ecosystem and Global Change Research Station of Fujian Normal University in Chenda, Sanming, Fujian Province, to explore the effects of warming and N addition on the concentrations and stoichiometry of C, N and P in fine roots of Chinese fir (Cunninghamia lanceolata) seedlings. The results showed that warming increased the concentration of fine root N in spring, but did not affect fine root C and P concentration. Warming decreased C∶N ratio but not N∶P ratio of fine roots in spring. Nitrogen addition increased the concentration of fine root C and N but not P concentration in spring, N addition decreased the C∶N ratio and increased N∶P ratio of fine roots in spring. The interaction between warming and N addition had a significant effect on C concentration of fine root in 1-2 mm diameter class, but not 0-1 mm diameter class. The effects of the interaction between warming and N addition had no significant effect on the concentration of fine root N and P. Our results suggested that warming and N addition could promote nutrient cycling of subtropical forest ecosystem. Nitrogen addition did not change N limitation status of subtropical Chinese fir plantation. The interaction between warming and N addition had different effects on fine root C, N, P elements, which was regulated by seedling C investment tradeoff and the dilution effect.

Key words: landscape pattern, land surface temperature., forest city