Abstract: In order to identify the effect of dung extracts of yak and Tibetan sheep on seed germination and seedling growth of six plant species in alpine meadow in the Eastern Qilian Mountains, the dung extracts with different concentrations (0, 25%, 50%, 75% and 100%) were used to treat the seeds and the indices relating germination and seedling growth were measured. The results showed that the effect of dung extracts differed with the change in treatment concentration. Treating with high concentration (from 75% to 100%) extracts of Tibetan sheep dung, the germination percentages of Elymus nutans, Achnatherum inebrians and Pedicularis kansuensis were significantly inhibited. The germination potential of E. nutans was inhibited with the concentration of extracts from 25% to 100% of the yak dung and Tibetan sheep dung, the germination potential of A. inebrians was inhibited with the extracts from 75% to 100% of yak dung and from 50% to 100% of the Tibetan sheep dung. The extract concentrations of Tibetan sheep dung from 25% to 100% and yak dung from 50% to 100% inhibited the seed germination potential of P. kansuensis. The seed germination index of P. kansuensis was significantly inhibited with 100% concentration of Tibetan sheep dung extract. Both Tibetan sheep and yak dung had no effects on the seed germination percentage, germination potential and germination index of Rumex acetosa and O. ochrocephala. 25% of yak dung extract promoted the root growth of E. nutans; 100% of Tibetan sheep dung extracts inhibited the plumule growth of A. inebrians, 100% of the yak and Tibetan sheep dung extract inhibited the plumule growth of P. kansuensis, 75% to 100% of Tibetan sheep extracts inhibited the root growth of A. inebrians and P. kansuensis. The growth of R. acetosa plumule and root was promoted with the concentration of extracts from 25% to 100% of the yak dung and Tibetan sheep dung, while other concentrations had no effect. Collectively, the effects of yak and Tibetan sheep dung extracts on seed germination in alpine meadow have three kinds of action: promotion at low concentration, inhibition or no effect at high concentration, which in turn potentially affects the seedling establishment, interspecific competition and community structure.

Key words: export coefficient method, slope gradient, non-point source pollution, Hujiashan small watershed, measured data