ABSTRACT
A factorial nitrogen and water addition experiment was carried out with one year-old Machilus pauhoi seedlings from Suichuan County, Jiangxi Province, with six treatments being established: two water levels with 80% and 40% of field moisture holding capacity and three nitrogen addition levels of 0, 50, 100 kg N·hm-2. Specific root length, specific root area, average diameter and tissue density of three fine root orders of M. pauhoi were measured to understand the main and interactive effects of short-term nitrogen addition and drought stress on root characters of M. pauhoi seedlings. The results showed that average fine root diameter and specific root length differed significantly among fine root orders. With the increases of root orders, the average root diameter increased, with the maximum being present in the third order (0.97 mm), but specific root length decreased, with the minimum being present in the third order (238.99 cm·g-1). No significant effects of nitrogen addition on specific root surface area, average fine root diameter, specific root length and root tissue density were observed. There were significant effects of water treatments on average fine root diameter, specific root length and root tissue density. Drought stress significantly increased average diameter of the third order fine roots of seedlings and decreased root tissue density of the first and second order fine roots. Specific root length of the third order fine roots in arid environments was significantly lower than that under the normal water supply condition. There was no interactive effects of nitrogen addition and drought stress on fine root morphology of M. pauhoi.