[Effects of drought stress on the stoichiometric characteristics in different organs of three shrub species].

In order to explore how water stress affects the stoichiometric characteristics in leaves, stems, very fine roots (0-1 mm), fine roots (1-2 mm) and thick roots (>2 mm) of three shrub species, we studied the effects of three water treatments [(75±5)%, (55±5)% and (35±5)% of field water capacity (FC)] on the stoichiometric characteristics of different organs of , and in a pot experiment. The results showed that there were significant differences in nitrogen (N) and phosphorus (P) contents, C:N, C:P and N:P of the same organ among the three species. With the intensification of drought stress, there was no significant change of C content in all organs of the three species. The N content increased in leaves, but decreased gradually in stems. The N content in very fine roots and fine roots increased first and then decreased. The P content decreased in leaves and stems, while increased first and then decreased in very fine roots and fine roots. Under drought stress, leaf C:N decreased, C:P and N:P of leaf and stem increased. There was the strongest effect of drought stress on the C:N of very fine roots and C:P and N:P of leaves. There was the least effect of drought stress on C:N, N:P of thick roots and C:P of very fine roots. There was no significant correlation between the contents of C, N in soil and the contents of C, N and P in shrub organs, but soil P content was significantly correlated with the contents of C, N and P in leaves and roots. It was concluded that the relative P limitation in soil was the most important factor affecting the stoichiometric characteristics of shrub organs. Drought had different effects on the stoichiometry of different organs in different shrub species. The stoichio-metry of leaves and very fine roots was more sensitive to drought stress than that of other organs. Drought might affect the stoichiometric characteristics especially related to P in different organs of shrubs, mainly by affecting plant absorption of soil P and its distribution in different organs.