Effects Of Nitrogen Additions On The Propagation And Soil And Water Loss Of Bothriochloa Ischaemun Population

The increasing atmosphic nitrogen(N) depostion is altering the terrestrial ecosystem.However, it is not clear how the N deposition will influence the conservation function of soil and water by changing the grass community characteristics and soil properties. Based on four levels of the N addition treatments(0, 2.5, 5 and 10 g N m-2 year-1) for two years, the effect of N addition on the population characteristics, soil physical and chemical characteristics and the soil and water loss of Bothriochloa ischaemum population was studied. The main results could be drawn as follows:There were significant effects of N addition on density, height and biomass of Bothriochloa ischaemum population. While the biomass increased, reached maximum in 5.0 g N m-2 year-1 treatment; N addition had changed the nutrient allocation strategies of Bothriochloa ischaemum, meanwhile, root-shoot ratio decreased with the increments of N addition; N addition had promoted sexual reproduction and vegetative propagation, thus it would lead to high ability of breeding and competition.N addition had promoted tiller, while the cluster diameter increased, reached maximum in 2.5 g N m-2 year-1 treatment; The results showed that moderate N addition will promoted population growth and development, and advantageous to the function of keeping water and soil of Bothriochloa ischaemum population.N addition cannot improve the soil nutrient content. The soil pH and soil organic matter could be reduced with the N addition. With the increase of N addition, the total nitrogen and the NH4+-N, the N03--N contents was increased. Besides, with the increase of N addition, soil total P content were not obvious.N addition could effectively control soil erosion. Compared with the bare plot(CK),runoff and sediment rate in N addition plots were reduced by 45-62% and 83-95%,indicting that Bothriochloa ischaemum plots had stronger effect on reducing sediment than reducing runoff.N added by influencing the physiological and ecological characteristics of Bothriochloa ischaemum, change height, density, biomass, root length, root surface area, undergrounddensity index to influence the function of keeping water and soil.