The Effect Of Different Improving Measures On Nutrients And Its Ecological Stoichiometry Of Degenerated Leymus Chinensis Steppe

As to the improvement measures of natural recovery,harrow,shallow plough and sowing L.chinensis 26 years later on the degenerated steppe of Leymus chinensis, I measured the community characteristics, under-ground biomass, nutrient of soil,plants and roots and its stoichiometric ratio, and compared with the grazing that outside the fencing. The objective of the experiment is to research the effect on of the nutrients and its stoichiometry under different measures, reveal the order and directions of the succession, optimize the current improvement strategies and aims to promote the grassland improvement to benefit the needs of mankind. Further more, through comparison of the four improvement measures, it can provide scientific evidences for controlling, recovering and boosting productivity of grassland, and seek the optimal way for recovering the degraded grassland.1. The biomass, density and litter of communities that after improvement strategies significantly improved than the grazing (a=0.05). The aboveground biomass and litter in the enclosure were:natural recovery> harrow> shallow plough> sowing L.chinensis. High-quality forages in natural recovery and harrow had a high fraction. The density of communities were:natural recovery> harrow> sowing L.chinensis>shallow plough. The diversity indexes and evenness indexes had no significant difference among four improvement strategies and the grazing (a=0.05).2. The impact of different measures on plants nitrogen content was higher than the phosphorus. Through the N/P, we know the area was short of nitrogen on the whole. Further more, harrow, shallow plough and sowing L.chinensis were even worse than the natural recovery.3. The underground biomass in different treatments was:natural recovery> harrow> shallow plough> sowing L.chinensis>grazing. Most of the underground biomass were fastened on the topsoil in all treatments, and the biomass dramatically reduce with increase in soil depth. Further more, the significant differences among the treatments also disappeared as the increase of soil depth. The underground biomass/aboveground biomass in different treatments was:the outside fencing significantly higher than all measures that the enclosures. There were no significant differences among those measures enclosures of underground biomass/aboveground biomass(a=0.05).4. The content of soil organic matter, total nutrient and available nutrient in different treatments were all reduce with the increase in soil depth and the significant differences among the treatments also disappeared as the increase of soil depth. The outside fencing significantly lower than all measures in the enclosures, the natural recovery was the highest in soil nutrient of the four enclosures. There were no significant differences among those measures enclosures of stoichiometric ratio for soil nutrient(α=0.05). The relationship among the soil indexes showed that there was a lack of N in all treatments.5. The overall relationship among the soil nutrient, plants nutrient, aboveground biomass and the density of communities showed that the plant nutrient just effect the density of communities, and further more, the significant correlation only appeared in the shallow plough and sowing L.chinensis (P<0.05). The soil N limited the biomass of communities in natural recovery, harrow and shallow plough and had no effect of the density.