Study On Botanic Characteristics And Ecological Adaptation Of The Ornamental Grass Eragrostis Spectabilis

Eragrostis spectabilis (Pursh) Steud is a perennial grass species of the Poaceae (grass family), native to North America, also is an ornamental grass species with ornamental value and wide applying prospect. It has been used for ornamental purposes in United States. In recent years, it was introduced into Beijing area as ornamental grasses resources. But till now we know littlle about botanic characteristics and ecological adaptation of E. spectabilis, it limits the scientific cultivation and application of E. spectabilis. In order to resolve this question, the basic botanic characters of E. spectabilis were observed in field conditions, and the potential geographic distribution of E. spectabilis in China was predicted. Ecological adaptation of E. spectabilis was analysed through germination characteristics, shade-tolerant and soil nutrien stress. Finally, the ecological adaptation of E. spectabilis in Beijing was summed up to provide a scientific basis and technical support for the scientific cultivation and application.The results showed that:(1) The phenological period of E. spectabilis was observed during the years of2011and2012, results showed that the species was able to adapt to the climate in Beijing, and could complete its life history normally. During the vegetative stage it did not show rapid growth characteristics; during the reproductive growth stage the species produce large amounts of seeds, which showed that it had strong ability to reproduce. The distribution of E. spectabilis in its origin areas could be well predicted by using ecological niche models. And the potential distribution of E. spectabilis in the Cetral and East China had high suitability.(2) Using germination percentage and germination index as evaluated indicators, the optimum germination temperature of E. spectabilis was35℃. According to the seed germination thermal model (T,℃), the germination temperature range was between17.7～43.2℃, with the best temperature of39.2℃. Light was favorable for seed germination, the germination percentage was relatively higher under continuous light condition than continuous dark condition. PEG6000-simulated water stress significantly inhibited the germination. When water potential decreased to-0.8MPa, seeds could not germinate. The soil depth of0.5cm was ideal for germination and the germination percentages from0-1cm were more than60%. The germination percentage decreased significantly with the increase of soil depth between1-4cm.(3) E. spectabilis were cultivated under four light intensity regimes (four shading treatment:0%,50%,75%and90%, which separately show100%,50%,25%and10%of full light) for two years. Results showed that with the irradiance decreasing, height and width were increased, and height fell to the lowest under90%shading treatment during the second growth season. Tillers and seed yield were decreased along with an increase in shade, and the differences are significant; the shading significantly increased chlorophyll content, leaf area, the photosynthetic rate and other related index (Gs:stomatal conductance, Ci:Intercellular CO2concentration); biomass were decreased along with the decreasing irradiance, but root-shoot ratio decreased under50%shading treatment and increased again under75%and90%shading treatment. The results suggested that the requirement of E. spectabilise to light is higher and growth was better under more50%of full light. Less25%of full light significantly inhibited the growth of this plant, and some plants even could not survive under10%of full light.(4) Sandy loam (treatment number:T1) and river sand (treatment number:T5) was as the basic soil. The two kinds of soil are mixed uniformly according to the mass ratio of1:1(treatment number:T2),1:2(treatment number:T3) and1:3(treatment number:T4). The Growth, Photosynthetic Characteristics, and Biomass of E. spectabilis on different Soil fertility was studied. Results showed that plant height, width, tillers and seed yield were decreased with the increase of the soil fertility, and show significant difference to contrast. The treatment decreased chlorophyll content, the photosynthetic rate, stomatal conductance and intercellular CO2, but water use efficiency increased. Intercellular CO2and water use efficiency differented significantly. Biomass were lowered significantly under soil nutrien stress, but root-shoot ratio decreased under T2and increased again under T3, T4, and T5. The results suggested that the requirement of E. spectabilis to soil nutrien is lower and Plants tolerate infertile, poor soils. The soil fertility less than T4treatment hardly inhibited the growth of this plant, and some plants even could not survive unde T5.