The Study On The Influnce Of Different Irrigation Frequency And Mixed Density To K.Cristata Lawn Stability

The study for the influence of seasonal dynamics and the years dynamics of Koeleria cristata L.+Viola prionantha Bunge mixed lawn’s ecological and physiological characteristics under three irrigation frequency and two mixed ratio conditions, with Poa pratensis L.+Viola prionantha Bunge mixed lawn as control, were presented during 2012 to 2014.Obtained the following conclusions:(1) The water potential of Koeleria cristata L. populations were lower than Viola prionantha Bunge populations, under different irrigation frequency. The different irrigation frequencies had no significant effect on the leaf water potential of Koeleria cristata L. and Viola prionantha Bunge populations.(2)The photosynthetic rate of Koeleria cristata L. was significantly higher than Viola prionantha Bunge in the same irrigation frequency under different irrigation frequency. Different irrigation frequencies had no significant effect on photosynthetic rate of Koeleria cristata L. population and WUE of Viola prionantha Bunge population. The transpiration rate of Koeleria cristata L. was significantly reduced; WUE of Koeleria cristata L. was significantly higher than other treatments and significantly higher than the Viola prionantha Bunge population, under interval of 15 days irrigation frequency.(3) In an age (2012) of Koeleria cristata L.+Viola prionantha Bunge mixed lawn, the relative number of tillers and height of Koeleria cristata L population are higher than that of Viola prionantha Bunge population under interval of 10 days irrigation frequency.10 days irrigation frequency was the most beneficial for Koeleria cristata L. to gain competitive advantages and inhibitted the growth of Viola prionantha Bunge effectively. Sufficient irrigation (interval of 5 days irrigation frequency) was benefit for growth and sexual reproduction of Viola prionantha Bunge. In two age (2013) mixed lawn, Interval of 15 days irrigation frequency was the most beneficial for Koeleria cristata L. and suppressed Viola prionantha Bunge. In the third age (2014) mixed lawn, the coverage of Viola prionantha Bunge population were higher than Koeleria cristata L. population under different irrigation frequency. The total biomass and the aboveground biomass of Viola prionantha Bunge were higher than Koeleria cristata L. In short, after three years of different frequencies irrigation treatments and interspecific competition, the numbers of Koeleria cristata L. population declined, andindividual saving rate fluctuated between 56.25%～62.5%. The number of Viola prionantha Bunge population increased, individual saving rate fluctuated between 195.88%～ 333.38%. The dominance of Viola prionantha Bunge is greater than Koeleria cristata L., and Viola prionantha Bunge becomes dominant species. In the third age of P.pratensis mixed lawn, the number of relative tillers, height and biomass of P.pratensis were significantly higher than Viola prionantha Bunge. Poa pratensis L. had become the dominant species in the interspecific competition.(4)Under different density ratios of one age mixed lawn, Koeleria cristata L. didn’t appeare sexual reproduction, tending to increase the number of tillers to improve their competitiveness, while Viola prionantha Bunge increased the number of fruits to improve the competitiveness.The maximum tillers of Koeleria cristata L. in 1:2 mixed lawn is 20.78% higher than that in 1:1 mixed lawn, and the number of fruits of V.prionantha was 34.61% higher than that in 1:1 mixed lawn. After two years of competition, Koeleria cristata L. had become the dominant specie and V.prionantha become the companion specie, the lawn was more stable in the 1:2 mixed lawn. In the 1:1 mixed lawn, dominance index of Koeleria cristata L. and Viola prionantha Bunge have no significant difference, the lawn had no significant dominant and the lawn was still unstable.