Effect Of Different Treatments On Seed Germination Characteristics Of12Alpine Meadow Species

The alpine meadow ecosystem of the Qinghai-Tibet Plateau is extremely fragile with serious grassland degradation which is endangering the Plateau ecological balance and sustainable socio-economic development. Therefore, seed germination research under this harsh climatic regimeis crucial to the vegetation restoration and ecosystem maintenance on the alpine meadow of the Qinghai-Tibetan Plateau.The study involved3experiments which included:(1) the effects on germination of fresh rumen content from yaks and Tibet sheep,(2) the effects of their feces burial during winter on seed germination and seedling growth of species common to the eastern Tibetan Plateau alpine meadow, and (3) the effects of different physical and chemical treatments on the germination of dormant seeds to develop effective methods to break seed dormancy. Seeds of12common species were collected together with fresh rumen content and their fresh feces from three yaks and Tibet sheep that grazed there. Seed germination test (1) was conducted after seeds had been soaked in rumen content for one of six soaking periods (12,24,36,48,60and72h),(2) seed germination was tested after feces burial of seeds for a whole winter,(3) the focus was on those species which germination rate was low the early two experiments and seed dormancy was a likely cause. All the seeds were incubated under natural light conditions of8hours light at25℃and16hours darkness at15℃, for the germination period of5days. The results obtained are as follows.After soaking in yak and Tibet sheep rumen content, the seed germination and seedling growth of the alpine meadow species were affected by soaking time, seed coat characteristics and plant species. After soaking in rumen content, there was no seed germination of Kobresia capillifolia at any exposures of time, the germination rates of scarified (peeled or with the seed coat cut through) seeds of Oxytropis ochrocephala, Medicago ruthenica var inschanica(yak rumen content soaking), Carex enervis, Polygonum sibiricum and Anemone rivularis(yak rumen content soaking), complete seeds of C. enervis(yak rumen content soaking), and A. rivularis were significantly improved (P<0.05) but the duration of soaking was also important. Seed germination percentages of Elymus mttans, Pedicularis kansuensis, M. ruthenica, Achnatherum inebrians, Poa crymophila were significantly inhibited by any exposure to rumen contents. After soaking in rumen content, the germination indices of scarified M. ruthenica at12h treatment, O. ochrocephala and R. acetosa at12-24h treatment, K. humilis at24h treatment, P. sibiricum at24-48h treatment, C. enervis at12-48h treatment and A. inebrians at12-60h treatment were significantly higher than the control under yak treatments(P<0.05), scarified seeds of A. rivularis, O. ochrocephala and C. enervis were significantly increased at short duration of Tibet sheep treatments of the range from12to24h,12h and12h, respectively(P<0.05). Seedling shoot lengths of K. humilis, C. enervis and A. rivularis, seedling root lengths of C. enervis and A. rivularis were significantly promoted after rumen content soaking, with the increase in soaking time seedling growth of other species gradually decreased. With the increase of soaking time, germination rates, germination indices and seedling growth of12species were inhibited or there was no germination of all species.There were there effects of feces burial during winter on the seed germination characteristics of alpine meadow species. Germination of all species significantly promoted was as follows:germination rates of A. rivularis, germination indices of/3. sibiricum under Tibet sheep feces burial, seedling shoot lengths of P. crymophila under yak feces treatments, P. kansuensis and P. sibiricum buried both under yak and Tibet sheep feces, seedling root lengths of P. crymophila (under yak feces burial), P. kansuensis and O. ochrocephala under yak and Tibet sheep feces. After yak and Tibet sheep feces burial during winter, germination characteristics of12species significantly inhibited were as follows:germination rates of C. enervis, A. inebrians, M. ruthenica (Tibet sheep feces burial) and K. capillifolia (yak feces burial), germination indices of K. humilis, C. enervis, E. nutans, R. acetosa and M. ruthenica (yak feces burial), A. inebrians and K. capillifolia(yak feces burial), seedling shoot lengths of R. acetosa and M. ruthenica (Tibet sheep feces burial), seedling root lengths of K. humilis and M. ruthenica (Tibet sheep feces burial). After yak and Tibet sheep feces burial, seed germination rates of K. humilis, E. nutans, P. kansuensis and P. sibiricum, seed germination indices of A. rivularis, P. kansuensis, O. ochrocephala and P. crymophila, seedling growth of E. nutans, C. enervis and A. inebrians, O. ochrocephala (seedling shoot length) and P. sibiricum(root length) were not affected.Chemical treatments(different concentrations of NaOH and GA solutions) and physical methods (low temperature stratification and warm water soaked for10h,15h and30h) were used on K. humilis, K. capillifolia and A. rivularis seeds to find effective ways of breaking seed dormancy. The results showed that K. humilis seed germination rate was significantly increased by NaOH treatments (P<0.05), K. capillifolia seed germination rate was significantly improved (P<0.05) after4%NaOH soaking3h,5%NaOH soaking3h,4h. However, NaOH treatments had negative impacts on either seed germination rate or germination index of A. rivularis. There were no significant positive effects on seed germination rates of3species by GA treatment. Low temperature(4℃) stratification for1month and2month significantly enhanced seed germination rates of K. humilis and A. rivularis.4%and5%NaOH soaking for3-5h, low temperature stratification and warm water soaking significantly increased K. humilis seed germination index, while only4%and5%NaOH soaking for3-5h treatments significantly promoted K. capillifolia seed germination index, low temperature stratification for1month significantly enhanced A. rivularis seed germination index.In summary, yak and Tibet sheep rumen content soaking and their feces burial during winter enhanced, inhibited and not affected the seed germination and seedling growth of the alpine meadow species at Qinghai-Tibetan Plateau, which might influence seedling recruitment, interspecific competition, and the plant community structure of the eastern Tibetan Plateau alpine meadow. Two alpine meadow livestock has a positive effect on the alpine meadow seed germination and seed dispersal, and the effect of seed dispersal by yak is stronger than the Tibet sheep. Effectively methods of breaking Kobresia species dormancy are NaOH solution and appropriate cold stratification, while cold stratification can effectively break dormancy of A. rivularis.