RESUMO
We analyzed the contents and stoichiometric ratios of carbon (C), nitrogen (N) and phosphorus (P) in leaves and fine roots of Machilus pauhoi (an evergreen broad-leaved species), Cerasus campanulata (a deciduous broad-leaved species) and Fokienia hodginsii (an evergreen coniferous species) to compare the leaf and root stoichiometry and allometric relationship between different functional groups of trees. There were significant difference in the contents and stoichiometry of C, N and P in the leaves and fine roots among different functional groups. C content, C/N and C/P of the leaves and roots were the highest in M. pauhoi. N content and N/P of the leaves and roots were the highest in C. campanulata, whereas P content of the leaves and roots was the highest in F. hodginsii. The allometric relationship of C, N and P contents as well as their stoichiometric ratios between the leaves and fine roots showed significant difference, which was affected by functional difference. The allometric relationship between C/P and N/P with significantly different allometric indexes in leaves in seedlings of those three tree species, while the isometric relationship between the contents of N and P was found in fine roots. There were significant difference in the C, N and P stoichiometry between the leaves and fine roots. The allometric relationship between leaf C content and root P content in M. pauhoi was detected. C and N contents and C/N, N/P in leaves generally had the allometric or isokinetic relationships with C/N, N/P of fine roots. There were allometric relationships between the leaf C content and the root C, N and P contents in F. hodginsii. It was concluded that nutrient allocation between leaves and fine roots of C. campanulata was more strongly coordinated. The investment strategy of P for leaves and fine roots across those three tree species was similar. The results provided scientific reference for accurate nutrient management at seedling stage and efficient cultivation technique.
Assuntos
Nitrogênio , Fósforo , Carbono , Folhas de Planta , Raízes de Plantas , Plântula , ÁrvoresRESUMO
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.