Nitrogen Application Effects On Belowground Bud, Aboveground Shoot Or Ramet Density And Biomass Of Leymus Chinensis In Songnen Plains

Nitrogen is the most important nutrients that affects the growth, development and yield of plants in semi-arid areas. Excessive utilization on grassland and adverse environmental conditions will lead to grassland degradation, and soil nutrition, especially the nitrogen loss greatly. However, the reports that application of nitrogen affects growth and development of Leymus Chinensis are scare.In our study, the dominant species of northeast China, L. Chinensis, was conducted as the experimental material. We applied nitrogen at the different growth stage of L. Chinensis (5-20, 6-20, 7-20), in order to study the effect of nitrogen application on number and biomass of parent shoot and daughter shoot, then on the number of all types buds and young rhizome. With the data, we explored the mechanisms of clone growth and sexual reproduction of L. Chinensis, and provided evidence for resume and management of grassland.The main results showed as follows:1. In 1-2 months after nitrogen application, the density of horizontal apex rhizome buds and upswept apex rhizome buds were significantly increased; but at the end of growth season, the effects on these two buds were not significant; in all three applicated time of nitrogen, the effects of nitrogen on buds of axillary shoot was not significant during the whole growth season; in July 20th, nitrogen significantly increased density of axillary rhizome buds.2. Effects of nitrogen application in May 20th and June 20th on apex rhizome daughter shoot density were not significant, but which in July 20th significantly increased density of all types of daughter shoot.3. When growing in condition of good nutrition, L. Chinensis could increase density of rhizome node buds in order to increase population density.4. The increase in aboveground parental shoot amount was through rather decreasing the mortality rate than increasing natality in newly shoot, which partly resulted in higher aboveground biomass than the control.5. In condition of higher parent shoot density, nitrogen application did not affect the amount and length of young rhizome.6. All nitrogen application did not affect the current heading rate, but that in July 20th increased heading rate of next growing season.